brake reservoir sediment (red mud, rust, ???)

[brucecooner]

5 hours ago, cruiser54 said:

Do the braided lines also!!

I got my valve from Summit Racing. 

When the distro valve is removed, there are larger orifices for the fluid to flow through. 

 

 

Thanks!

 

It bugged me that I didn't know what was taking place under the bed (truck bed), so I crawled under the rear axle this evening and mapped out what goes where. 

Here's the result for the morbidly curious, it might even be correct.

 

 

I had to guess on which was the regular supply and which was the emergency bypass, but I figure the one going to the prop. valve has to be the regular.

And of course, these tubes are hideously complex on the truck, it's like a plate of spaghetti under there.

 

This appears simpler than I thought it would be though, as I think I just need to plumb the regular supply to the flex hose that then goes to the axle.

With the proportioning valve functionality moved up under the hood of course.

 

I'm not sure how much of the old tube I want to rip and replace. It looks like I'd have to drop the gas tank skid plate, and most of the tubing is wrapped in gravel guard too, which I should probably keep, especially across the axle.

 

 

[Eagle]

On 1/10/2023 at 2:21 AM, brucecooner said:

As well, the rear brakes are a little crusty. 

If I'm trying to restore braking function, I really should do something about them.

The hardware's not in horrible shape, but maybe new cylinders and shoes at the minimum.

Also given the gunk I found in the rear chamber of the old master cylinder, new cylinders are probably a good idea anyway.

 

The front calipers are fairly clean and I know they're grabbing good (the smell when I got out last time I drove it told me as much) so not as worried about them.

 

Fixing the rears would probably fix my stopping problem, but I've decided I just don't trust the distro block or the rear prop. valve.

During the bleed, I never saw the dash light come on to indicate the bypass valve had shuttled (and I did clean up the brake light connector while I was installing the new master cylinder.  Goodness knows if the valve is stuck in place or what's going on in there.

 

 

The swing arm on the rear load-sensing valve should be approximately horizontal (parallel to the axle).

 

For the rear, your shoes  have material left, but I would replace the wheel cylinders. Here's my view on why:

 

As with most (probably all) front disk/rear drum brake systems, there's a basic problem. Disk brakes are always adjusted. When you take your foot off the brakes, there aren't springs that move the pads away from the rotors -- all that happens is that the pressure is removed. That doesn't work for the rear, because the rear brakes are "servo assisted." This is why it's important to not get the front and rear shoes on each side reversed. When the vehicle is moving forward, once the shoes make contact with the drum the friction tries to rotate the whole assembly, and the geometry of the internal parts is such that the rotation increases the pressure. This doesn't happen in reverse, which is why your parking brake may hold the truck when you're pointing downhill, but not when you're pointing uphill.

 

So you have all those springs and things to pull the shoes away from the drum when the brakes aren't applied. But ... because the front pads are always ready to rock and roll, it doesn't take a lot of peddle movement to engage the fronts. Once the rear shoes get worn, they may not be making much (or any) contact by the time the front pads are fully deployed. The rear brakes are equipped with self adjusters, but those only work if you back up "smartly" and then slam on the brakes -- multiple times. I suspect that you, like most MJ drivers, are actually driving around using only the front brakes because the rears aren't properly adjusted. With my '88 XJ (which is by far my highest mileage of the fleet), I've replaced the front pads probably three times for each time I've replaced the rear shoes. Why? Because the rears aren't doing anything -- and I used to be sort of anal about adjusting them manually every few months.

 

One of the side effects of that is that the seals inside the rear wheel cylinders get gummed up and don't like to move. Once that happens, even if the shoes are properly adjusted you still won't have rear brakes. Wheel cylinders are cheap. Just replace them.

[brucecooner]

22 hours ago, Eagle said:

 

The swing arm on the rear load-sensing valve should be approximately horizontal (parallel to the axle).

 

For the rear, your shoes  have material left, but I would replace the wheel cylinders. Here's my view on why:

 

As with most (probably all) front disk/rear drum brake systems, there's a basic problem. Disk brakes are always adjusted. When you take your foot off the brakes, there aren't springs that move the pads away from the rotors -- all that happens is that the pressure is removed. That doesn't work for the rear, because the rear brakes are "servo assisted." This is why it's important to not get the front and rear shoes on each side reversed. When the vehicle is moving forward, once the shoes make contact with the drum the friction tries to rotate the whole assembly, and the geometry of the internal parts is such that the rotation increases the pressure. This doesn't happen in reverse, which is why your parking brake may hold the truck when your pointing downhill, but not when you're pointing uphill.

 

So you have all those springs and things to pull the shoes away from the drum when the brakes aren't applied. But ... because the front pads are always ready to rock and roll, it doesn't take a lot of peddle movement to engage the fronts. Once the rear shoes get worn, they may not be making much (or any) contact by the time the front pads are fully deployed. The rear brakes are equipped with self adjusters, but those only work if you back up "smartly" and then slam on the brakes -- multiple times. I suspect that you, like most MJ drivers, are actually driving around using only the front brakes because the rears aren't properly adjusted. With my '88 XJ (which is by far my highest mileage of the fleet), I've replaced the front pads probably three times for each time I've replaced the rear shoes. Why? Because the rears aren't doing anything -- and I used to be sort of anal about adjusting them manually every few months.

 

One of the side effects of that is that the seals inside the rear wheel cylinders get gummed up and don't like to move. Once that happens, even if the shoes are properly adjusted you still won't have rear brakes. Wheel cylinders are cheap. Just replace them.

 

That tracks with my experience.  When I bought it it didn't particularly care to stop.  Even less so now that I've "worked" on the brakes.  *ahem*

 

I had noticed there didn't seem to be any action from the cylinders when I was bleeding and son pressed the pedal.  My duh, non-mechanic self didn't put it together at that time though, replace the cylinders.

 

So yes, new cylinders for sure. The shoes aren't thick but seem okay so I'll roll with the existing ones for now.

The rest of the brake guts are not too awful rusty, but I'll have to see if I can get the adjusters to move and tune them out when everything is back together.

 

 

 

 

 

 

[brucecooner]

Waiting on parts now.

I got the Titan double flare tool, but practicing some flares I learned that the crappy nicopp line from Amazon is not up to the job, going to get some better stuff from Summit.

 

However, while I was mapping out the rear lines under the bed, I noticed that the final hard line that mates to the flex line that goes to the axle has this large upward loop (picture below).

(the soft line goes out of the bottom of the frame in the picture below, then continues back into the picture to the brass T on the axle in the background)

 

I'm suspicious that this might be a place for air bubbles to hang out and be very difficult to get out of the line.

 

 

I'm I'm trying to improve things here, would it be better to route this to remove this upward loop?

The metal plate on the right of that photo is the bracket that holds the original prop valve, and I'm wondering

if I could move this bracket from a horizontal mount to a vertical mount position on that bracket, and take out this high point in the line.

 

Also, are the brake fittings on a Comanche going to be 3/8 x 24 ?  I know there's a couple large ones (1/2 inch?) that mate the master cylinder to the distribution block up front, are there other mismatched sizes in the system?

[cruiser54]

The loop is not necessary and the fittings are standard. 

[Eagle]

12 hours ago, brucecooner said:

Waiting on parts now.

I got the Titan double flare tool, but practicing some flares I learned that the crappy nicopp line from Amazon is not up to the job, going to get some better stuff from Summit.

 

 

What did you get? I've bought CUNIFER brake line from Amazon and had zero problems with it. It's much easier to flare well than steel brake line.

[gogmorgo]

The upward loop shouldn’t cause problems for bleeding. Yes, air can accumulate there if there’s air in the line, but it’ll get pushed out while you’re bleeding. The inner diameter of the lines is small enough and brake fluid is viscous enough that air bubbles will move down the line, and brake fluid won’t scoot around them. And a good solid push while bleeding moves the fluid far enough that bubbles don’t really have a chance to creep back to where they were. 

[brucecooner]

12 hours ago, Eagle said:

 

What did you get? I've bought CUNIFER brake line from Amazon and had zero problems with it. It's much easier to flare well than steel brake line.

It was the 4LimeTimes (?) stuff.

 

https://www.amazon.com/Copper-Nickel-Brake-Transmission-Tubing-Universal/dp/B07BMZBT3Q/ref=psdc_15721801_t3_B085GG7KZP?th=1

 

The business end of the flare looks okay-ish.  Some do come out a little oval shaped.

 

 

But they don't have the neat trumpet shape from the side view.

They have this almost spiral look to them, which makes me think that

since the punch/die is threaded into the tool, it is grabbing and twisting the line as it turns.

I took one out after the OP1 step, and that's when they develop this twist.

I did try using more die lube, thinking maybe it had too much friction and that was leading to the twist, but that didn't help.

 

I found a thread somewhere that indicated others had the same problems with Amazon sourced line...

https://forum.ih8mud.com/threads/titan-double-flare-tool-problem.1240821/

But then other people on that thread could also use stuff from Amazon without issue. I wonder if there are batch differences in different products or something.

 

That thread seems to indicate they have better luck with a Summit product.

https://www.summitracing.com/parts/urr-br-ez100

 

 

3 hours ago, gogmorgo said:

The upward loop shouldn’t cause problems for bleeding. Yes, air can accumulate there if there’s air in the line, but it’ll get pushed out while you’re bleeding. The inner diameter of the lines is small enough and brake fluid is viscous enough that air bubbles will move down the line, and brake fluid won’t scoot around them. And a good solid push while bleeding moves the fluid far enough that bubbles don’t really have a chance to creep back to where they were. 

 

Good to know in case I don't have the guts to redesign a lot. 

The amount of bending and rerouting I do under the bed will ultimately depend on how much energy I have after working up front.  :)

Cuz I don't know if I have enough mechanical mojo to run a line alllll the way from the engine bay to the back.  I need to drop the gas tank skid plate and see what I'm up against, which would be a good quick project while I wait on parts.

 

I have noted that were I lazy, I could go to the tee that combines the bypass line with the prop. valve output and goes to the axle, just block off the

prop. valve input side (thus removing the old prop valve from the system), and then just connect the bypass line start up at the front to the new prop. valve under the hood.  So it would go:  new prop. valve (front) -> bypass line -> tee (under bed, with one input blocked it's effectively just a union) -> axle, achieving the desired result. 

Super lazy, like I said. 

 

 

 

 

 

[brucecooner]

In case anyone else in the future is foolish enough to try replacing the master cylinder on their '88 Comanche and goes looking for fittings, I figured out the port sizes.

Front: 1/2 x 20

Rear: 7/16 x 24

Very likely the same on a Cherokee.

These sizes are reversed at the attachments to the distribution block.  Goodness knows why.

I also enshrined it in a picture that might helpfully appear in image searches.

(I also did this so that I can remember it too.)

 

I've got some steel nuts that came with the crappy tubing and look like they'll be covered with rust in a week.

Why is it so hard to find these sizes in brass?

 

[brucecooner]

On 1/17/2023 at 7:16 PM, gogmorgo said:

The upward loop shouldn’t cause problems for bleeding. Yes, air can accumulate there if there’s air in the line, but it’ll get pushed out while you’re bleeding. The inner diameter of the lines is small enough and brake fluid is viscous enough that air bubbles will move down the line, and brake fluid won’t scoot around them. And a good solid push while bleeding moves the fluid far enough that bubbles don’t really have a chance to creep back to where they were. 

About that...

 

Oh, yes, I'm still struggling through this brake job.  The weather got cold and I got sick (still dealing with it) which has meant my poor Comanche has been driveway decoration for months now. 

Yes, everyone point and laugh that it's taken me like, four months to do this, (even I think it's sad) then when you all have your breath back let me ask about something.

 

For the front lines, the line comes out of the master cylinder port then goes down toward the location of the old distro block.

Down there it meets a T, which sends one line down to the driver's side front, and the other line exits the T straight back toward the firewall.

This line headed for the passenger side caliper line runs beside the booster then turns UP, basically following the route of the original line, turning passenger side just below the pinch seam, and following it for a while before turning down before it goes around the charcoal cylinder and out the passenger wheel well.

 

Note that it no longer passes through a distro block (that thing is gone).

 

The line headed to the rears comes out of the m.c. (front port) goes under and around to a proportioning valve right next to it, that is currently closed.

From that valve a line goes down and meets the original bypass line to the rears, which is plugged at the back until I get new rear hardware.

And don't worry, I have wrapped fuel line around the booster bolt/nut so the brake line isn't rubbing metal there.

And note that this picture was made during a test fit, hence why there's no tape on the NPT adapters on the valve.

 

 

Anyway, getting to my quandary.

I bled the front lines today and could NOT get the pedal to stiffen up.

I was getting solid flow without any air bubbles out of the bleeders at both front calipers.

But the pedal is going nearly to the floor, is very soft.

The calipers do grab, and after jacking up the fronts and verifying they do stop the front wheels, I very slowly eased it around the neighborhood.

But that pedal is super soft and the fronts just aren't grabbing and stopping was iffy at best.

 

Which leads me back to what gogmorgo wrote.

My front passenger line goes UP to run along the firewall, then DOWN to meet the wheel, giving it a length of high spot.

 

I'm suspicious that all that upward bend may contain an air bubble that's not moving.

Like I said, the rear line is closed at the prop. valve, which I think would mean that short segment between m.c. and valve is holding pressure.

 

But, like gogmorgo said, it would be very hard for very much viscous fluid to slip past an air bubble in a tiny 3/16 inch line.

 

Note that I followed the route of the original line, it's even snapped into the original clips, so this shouldn't be some new problem I've introduced.

 

I'm going to bleed them again, and probably give the high part of the line a few light taps as I work to hopefully loosen any bubbles.

 

But if anybody has any ideas about why the softness persisted I'm all ears.

 

 

 

 

[cruiser54]

After 1/2 cup of coffee this morning, I'm thinking you shouldn't bleed until the rear brakes are plumbed in. 

 

Cold in Goodyear???  You shoulda felt what it has been like up here!!

 

Where did you get the adjustable prop valve? 

[gogmorgo]

How hard is it to slip your hand through the air? That’s about how hard it is to push air out of a thin tube. Having an upward loop in the lines shouldn’t be causing problems. 
 

Starting at step one, we know the master cylinder is pushing fluid? You can bench bleed on the truck with a short length of brake line running from the port back to reservoir. If it’s been pushing back and forth dry it’s possible the seals got damaged. Depending on the level of damage it’s possible the thing could hold just enough pressure to move it with no resistance to flow but not be able to put much pressure into the system with it closed. 

 

I’m a little skeptical of NPT fittings in a brake system. Spiral leak path, could potentially be causing problems although generally if air is going in fluid would also be coming out the same place. 
 

2 hours ago, cruiser54 said:

 

Cold in Goodyear???  You shoulda felt what it has been like up here!!

Being outside in any sort of cold while sick is the worst.
I was just up in Resolute, Nunavut. For reference, it’s further north than the northernmost point of land in Alaska. Without much comment on temperatures, it’s gonna be at least three months yet before the ocean thaws enough for boats to get in. And there’s no trees to block the wind up there either. Laying underneath a truck in the snow to diagnose a 4x4 issue was… a time. 

[brucecooner]

7 hours ago, cruiser54 said:

After 1/2 cup of coffee this morning, I'm thinking you shouldn't bleed until the rear brakes are plumbed in. 

 

Cold in Goodyear???  You shoulda felt what it has been like up here!!

 

Where did you get the adjustable prop valve? 

My cold is not most peoples' idea of cold.  I start shivering at about 65 degrees, it's ridiculous.  It also didn't help that it decided to rain on almost every, single day, I thought I might go out and fiddle with the truck.  I appreciate the precip but its timing was poor.

 

The mini prop valve came from Speedway.  I actually live a few miles from the warehouse here on the west side.

https://www.speedwaymotors.com/Speedway-Compact-Adjustable-Brake-Proportioning-Valve,1979.html

This valve was used by someone else around here who gave it high marks.

 

I did get the big Woodward(?) one, but could NOT find a place to mount it, while the mini one slipped in right next to the cylinder. I can still get the big ole stock windshield washer reservoir back in.  Well, if I were to ever get done with this brake job I could.

 

I did briefly debate mounting a valve under the rear end, where I could reach beneath the wheel arch and work it, but didn't consider that a good long term arrangement.

 

 

4 hours ago, gogmorgo said:

How hard is it to slip your hand through the air? That’s about how hard it is to push air out of a thin tube. Having an upward loop in the lines shouldn’t be causing problems. 
 

Starting at step one, we know the master cylinder is pushing fluid? You can bench bleed on the truck with a short length of brake line running from the port back to reservoir. If it’s been pushing back and forth dry it’s possible the seals got damaged. Depending on the level of damage it’s possible the thing could hold just enough pressure to move it with no resistance to flow but not be able to put much pressure into the system with it closed. 

 

I’m a little skeptical of NPT fittings in a brake system. Spiral leak path, could potentially be causing problems although generally if air is going in fluid would also be coming out the same place. 
 

Being outside in any sort of cold while sick is the worst.
I was just up in Resolute, Nunavut. For reference, it’s further north than the northernmost point of land in Alaska. Without much comment on temperatures, it’s gonna be at least three months yet before the ocean thaws enough for boats to get in. And there’s no trees to block the wind up there either. Laying underneath a truck in the snow to diagnose a 4x4 issue was… a time. 

The m.c. is definitely pushing fluid, but at what pressure I couldn't say.

I didn't give any context to the bleed procedures... there's so much more to this saga.

 

I did have this cylinder on the truck when I had only replaced the booster and cylinder (no lines or other hardware).

At that point it had been bench bled. I used the procedure from the included instructions though. You put little red plastic plugs in the ports, add fluid, and slowly

work it back and forth until no more bubbles come up into the chamber.

 

Once I realized the "new" booster was leaking worse than the 30-year old one, I decided to ditch the distro block and run lots of new lines.

So I ordered a new booster, and at the same time ordered new rear brake cylinders (from Crown), but my plan was to replace the cylinders at a later time so I could get back on the road sooner.

Anyway, the new master cylinder came off the truck, the port plugs went in, and the cylinder was stored in a sealed ziploc bag in the garage, still with fluid inside, while I learned how frustrating it is to run brake lines.

The cylinder never sat up dry and was in an airtight bag the whole time.

Fast forward a bit, and upon finding out I need to run new lines on the rear axle, I decided to replace all the rear hardware too.

So I order rear hardware kit (Crown Mfg. again) and discovered it was gonna be like three weeks till it even ships.  Argh.

So I formulate a brilliant plan to...

1. mostly drain the m.c. so it's not holding onto much of the  fluid that was in the old crusty lines

2. bench bleed the rear chamber while on the truck (using the port plug procedure) to pressure test the rear line, since its fittings would be easier to reach before final plumbing on the front line

3. bench bleed and pressure test the front lines and, hopefully, have just enough brakes to let me ease around the neighborhood

 

So I did mostly drain the front and work the cylinder with it in that state while bleeding the rear chamber, but the seals and everything were still wet as I didn't completely drain the front chamber.

 

Those NPT fittings, yeah.  Apparently others have used them with success. I will say the cylinder side fitting tape was visibly wet the day after my initial pressure test and there was a tiny drop of fluid on the bottom.  I loosened the flare fitting and cranked the NPT fitting down some more, hopefully that will do the trick.

 

I just talked to Summit today, but there's still no ship date on my rear drum hardware, argh. If it don't ship soon I'll have to cancel and find another source.

It's a Dana 44 rear so have to get the 10x2.5 hardware.

But I should go ahead and at least plumb the rear axle and install the new rear cylinders, so the whole system can be pressurized out to all the wheels.

And the old hardware will work just fine, I just wanted shiny new stuff on all four corners.

 

But I did at least ease it gingerly around the neighborhood yesterday!  That felt like progress.

 

But since The Heartbreaker (the truck's name) always has a surprise up its sleeve, it decided to idle at 1500 rpm for the test run.

I thought oh great, another leaking booster, but back in the driveway I pulled the line to the booster and put my thumb over it but it was still idling high.

Just something in the control system was out of its head.

After a while warmed up, with few moderate revs the idle settled back down to its usual 500-700-500-700 cycle.

God this truck just, argh!

I've halfway given up on ever getting this thing out of the neighborhood. 

It might as well be one of those theme park rides where you crawl around a premade track in a little gokart.

 

Anyway, I do NOT envy you having to freeze your fingers off on metal parts while dodging polar bears on the arctic waste.

I'll take a walk around my neighborhood in 100 degree air over that any day.

 

 

 

 

[gogmorgo]

Polar bears aren’t much of a concern on land, they’re mostly out hunting on the sea ice. Or so I’m told. But I’ll take the cold over the heat any day. You can always put more layers on, but you can only pull so many off.
 

I’d missed that little detail. I don’t really know what sort of effect having the rear line blocked off would have, but I have a hard time imagining it would be good, at least if it’s been bled at all. If it’s bled completely then it would be trying to compress something incompressible. Probably not the case because the pedal would be rock hard once the MC passes the fill port. If there’s a lot of air in the line (or it’s just open) it would squeeze it down as far as the front cylinder allows it to travel. If it’s got somewhere between those two ends of the spectrum, I imagine it would squish the air until it can’t compress much further, which may not be allowing for the full stroke of the master cylinder, impeding proper front brake bleeding and performance.

[brucecooner]

The ETERNAL BRAKE JOB continues.  I am nothing if not persistent.

 

Still don't have brakes (more on that later), but I FINALLY got brakes lines everywhere brake lines are supposed to be, and got the rear drums pointlessly rebuilt with shiny new hardware.

Man, reassembling drum brakes is like trying to stuff everything back into an old timey pocketwatch.

 

It's not horrible under the back. It looks clean with the crusty old prop. valve gone (now have one under the hood).

I got gravel guard on all the lines so they look correct, and I at least figured out not to run lines directly between the axle and the bump stop.

The rear lines are now running from the previous bypass/emergency line to the rear, which was much cleaner than the main line.

I tried as hard as I could, multiple times, to remove that tee from the line so I could use a simple union, but the fitting on the master (supply) side would NOT budge with any amount of penetrant, patience, heat nor hammering.

I finally said eff it and plugged off the now unused side, then ran the other side out to the hose.

 

 

Anyway, everything is now plumbed and nothing leaks (so far), and I've bled quite a bit, but the brakes are still effectively non-functional.

After plumbing was done, I re-bled the master cylinder with it in the truck, with fittings that ran lines back into the reservoirs and making my son pump the brakes until there was no more air coming out of either port.

I then re-attached the lines to the ports and bled all the corners, farthest first (though now that the front/rear are on separate lines I can tackle the ends in any order).

I did some of the bleeding with a vacuum pump (tricky), but I'd always follow that up with a few applications of the old "push the brake pedal in with a plank of wood then go to the wheel and crack the bleeder" trick.

All four corners show a solid flow of fluid when you open the bleeders with the pedal down.

The new prop valve is over half open, and I was definitely getting fluid at the rears so don't think the valve is a hindrance.

I left only a little clearance between the new drums and shoes, and if you jack the rears up and spin a wheel then press the brakes they do grab enough to stop the wheel.

Same on the fronts, you can spin one then press the brake and it will stop.

 

But still, the pedal goes pretty much to the floor, it has no stiffness at all, and there just isn't much pressure behind what fluid gets pushed through.

I can drive it, slowly and gingerly, around the neighborhood, but that's it.

 

So I've had a lot of practice at bleeding brakes, but no luck so far, and have no idea where the air bubble or bubbles might be.

At this point my options seem to be starting over by pulling the cylinder, emptying the darn lines of fluid, then just starting again from step one,

or sell this darn thing to the next sucker who wants to spend every spare evening and weekend of the rest of their life trying to get it roadworthy.

 

Anyway, are there ANY diagnostic tools that might help me determine where the softness is coming from?

 

I am wondering if, after bleeding the master cylinder, when I removed the bleed fittings from the cylinder I basically just undid all my work and let air back into the cylinder.

But if that's the case, how DOES one attach lines to a freshly bled m. cylinder without getting air all in it?

 

Also, just because I'm getting fluid out of a cylinder does not mean there isn't air left somewhere up the line, and maybe I actually need to keep bleeding more to get that air bubble to the end of the line and out the bleeder.

 

Argh!  If I ever get this done I hope I never see another drop of brake fluid in my life.

 

 

 

 

[cruiser54]

Did you have the calipers off the truck? 

Just asking because if they get put back on upside down on the opposite side from where they belong, they'll never bleed. 

[gogmorgo]

You should be able to re-bleed the master after the lines are hooked back up and the rest of the system is bled, same as you would at the wheels by stepping on the brakes and cracking the fittings, letting them squirt. Just make sure to wash all the fluid off or it’ll wreck your paint. 
 

I’m running out of ideas. Unless the master cylinder is toast, or mismatched size to the calliper/wheel cylinders, or maybe the brake booster is over boosting, but the brakes should still work. Could also be a mechanical issue with the pedal I suppose. 

 

[gogmorgo]

You should be able to re-bleed the master after the lines are hooked back up and the rest of the system is bled, same as you would at the wheels by stepping on the brakes and cracking the fittings, letting them squirt. Just make sure to wash all the fluid off or it’ll wreck your paint. 
 

I’m running out of ideas. Unless the master cylinder is toast, or mismatched size to the calliper/wheel cylinders, or maybe the brake booster is over boosting, but the brakes should still work. Could also be a mechanical issue with the pedal I suppose. 

 

[brucecooner]

17 hours ago, cruiser54 said:

Did you have the calipers off the truck? 

Just asking because if they get put back on upside down on the opposite side from where they belong, they'll never bleed. 

Yep. The calipers and cylinders are new, but I was very particular to get them on right. The bleeders are all higher than the fittings and banjo bolts, which I take as a sign I got it correct.

 

 

11 hours ago, gogmorgo said:

You should be able to re-bleed the master after the lines are hooked back up and the rest of the system is bled, same as you would at the wheels by stepping on the brakes and cracking the fittings, letting them squirt. Just make sure to wash all the fluid off or it’ll wreck your paint. 
 

I’m running out of ideas. Unless the master cylinder is toast, or mismatched size to the calliper/wheel cylinders, or maybe the brake booster is over boosting, but the brakes should still work. Could also be a mechanical issue with the pedal I suppose. 

 

I did not know that trick of pressing the pedal then just cracking the m. cylinder fitting (essentially using it as a bleeder, I guess).

I'll definitely give that a try. 

 

The pedal travel is the same whether the engine is running or not, I don't think the booster makes any difference to it.

 

And I've been thinking about some sort of catch basin to fit under the cylinder.  When I pulled the lines last time I had about half a roll of shop towels stuffed under the cylinder, and still had to clean up a bunch of fluid.  I keep a bottle of water handy to splash on spots after I wipe up the brake fluid.  And then I wipe up the water.  My son has said part of my problem with it is that old Jeeps aren't supposed to be that clean.

 

I guess there's a chance the master cylinder might be toasted. 

It's a rebuilt one, but I got it at Autozone so, rolling the dice on it I guess.

It's odd to me that the cylinder allows as much travel as it does so easily. 

When I was bench bleeding it I had to really work to push it an inch, but that was without the mechanical advantage of the pedal.

 

I'd put "lack of mechanic's skill" above any part failure at this time though.

 

 

 

[Salvagedcircuit]

You are using a new Brake Booster, right?

Have you adjusted the booster push rod?

That was the end result of my WJ dual diaphragm brake booster upgrade saga. A1 CARDONE ships new boosters with rods fully seated. They are not adjusted from factory. You have to adjust the threaded center rod to match your master cylinder or your booster push rod will never push the master cylinder fully and pump. If you call their "ASE master technician support line" they will tell you how to prime the master cylinder, but they have no literature or documentation on their boosters. For a major corporation, it is unacceptable that they do not possess the documentation on the parts they make. It is possible that other booster manufacturers are also shipping boosters with push rods fully seated.

 

Booster push rod adjustment issues might pop up more on this forum in the future because there are very few bendix / mopar brake booster + master parts left. I ended up buying a dual diaphragm 1996 XJ era booster+master combo from omix-ada. It turns omix-ada still has the genuine mopar booster+master cylinders, but they are ~20yrs old from when the previous owner purchased what was left from a closing dealership nearby. Why I am mentioning this? The booster push rod in the omix part was properly adjusted to the master cylinder. It's possible that the mopar boosters were adjusted properly on purchase and owners never had to deal with adjusting the booster push rods in the past. It's clear to me that the 3rd party vendors are taking a vacation on QC or they are just enjoying slapping their logo on someone else's part.

 

I went through ~3 pints of brake fluid diagnosing my issues before I caved in and checked the booster push rod. I thought it was air in my lines but it was not. I thought it was my helper being sloppy with pumping or over torquing my brake bleeders, so I installed speed bleeders. I have to say, speed bleeders (brake bleeders with ball bearing checks inside) work wonders and are worth every penny. They made the job a lot easier, even with 2 people.

 

Cruiser54 has a document from lexus on how to properly adjust the brake booster push rod. This is the way to adjust it. I could not find a single piece of documentation from Jeep, AMC or chrysler on how to adjust the booster push rod. The lexus document is very detailed.

 

Before I adjusted my booster push rod, my pedal was like softserve icecream. I adjusted it and my brakes work properly now. I would seriously look into this. That's the conclusion to my problem. It might be yours too. I attached the document and post from @cruiser54 below.

 

[Salvagedcircuit]

On 9/15/2022 at 4:49 PM, cruiser54 said:

There is a critical measurement between the booster pushrod and the master cylinder. 

 

 

booster rod.pdf 607.64 kB · 8 downloads

 

[brucecooner]

4 hours ago, Salvagedcircuit said:

 

Thanks for posting that @Salvagedcircuit.  I read the doc and it makes sense.

If the booster rod contacts the cylinder piston after it has used up some of its throw, it won't have as much travel left to push the cylinder.

 

It's interesting you mentioned this, because the booster I bought from Crown was explicitly listed for an '88 MJ, BUT the body was a different shape than the one that came off. 

The body of the one I got was not as "deep", and had an adapter bracket on the back to make up for the narrower body, so it would still mate to the firewall correctly.

Everything still bolted back up, so I assumed it was okay, but now I'm wondering.

Also the end that attached to the pedal was subtly different, and I had to leave out the plastic bushing in the pedal switch, or the brake lights would be always on.

I left out the bushing and the brake light switch worked normally, but I should have been more suspicious.  By that point I was so tired of working on brakes I'd take anything that seemed to work, unfortunately.

 

So, my current plan is to remove the cylinder and double check it by plugging the ports and taking it through the bench bleed again.

If it's good and tight I'll know that's not the problem.

While it's off I can measure the cylinder depth and compare it to the booster.

 

I am very very curious about an aspect of bleeding though.

When I was bleeding the cylinder in the truck, I had clear lines from adapters on the ports over the top of the cylinder and back into the reservoirs, as normal.

I would watch and when my son pushed the brake pedal, fluid and a few little bubbles would come out of the ports and over into the reservoir, BUT,

when he released the pedal fluid would draw back through the lines and back into the port.

I would guess that's normal operation, when the cylinder returns the pressure it built into the lines backs off, and fluid travels back toward the cylinder.

 

Okay, say there's a bit of air in the line near the cylinder.

You press the brakes, the air in the line compresses a bit, maybe it gets pushed along a little.

But when you release the brakes, does that air not just "back up" back toward the cylinder?

Thinking about it, I guess the fact that the bleeder is open lets the air travel further toward the wheel every time you press the brake.

Because when you close the bleeder, the cylinder has to work against a closed system, and thus doesn't pull the fluid as far back.

 

Basically I'm wondering, if there is air near the cylinder, even though I'm seeing no bubbles at the wheel, I have to pull those bubbles alll the way to the wheel,

so I have to pull the whole contents of the line through before I even see the air.

Which reminds of the definition of insanity, keep doing the same thing expecting a different result.

I'm almost tempted to take push all the fluid out of the lines while I have the cylinder off, and just restart from scratch.  Now who's insane?

 

 

[Salvagedcircuit]

Order of operations:

1. Make sure you bench bleed the master cylinder
2. Measure your booster rod and adjust like in the lexus document. Add loctite or a group of washers then snug down the adjustable rod so it's not loose and changes position when the vehicle is moving. If you use washers make sure they are a  similar outer diameter to the shaft. The booster should have an adjustable knurled threaded bolt and a knurled shaft. Grab the knurled shaft and tighten the threaded bolt against it.
3. Have a helper push the brake pedal on the comanche, which pushes the booster rod out, then install the master cylinder. This way you properly line up the booster rod into the master cylinder. Keep the master cylinder level as best you can. You can install the master onto the booster with the booster bolted to the firewall. Or you can bolt the booster to the master on a bench table then install into the vehicle. It does not matter which way.
4. I did not do this at first, and my booster rod did not seat in the master cylinder and instead just scraped the outside body of the master cylinder. Yes, it is possible to install a booster with the rod miss-aligned, it will still bolt up. Take your time and make sure everything fits right.
5. I used speed bleeders because it's not worth the hassle of tightening and loosening the brake bleeder when pumping. It just becomes cumbersome. It's a whole lot easier to just pump and not have to worry about when to tighten on the back stroke of the brake pump.
6. Do not over tighten the brake bleeders. My brothers like to show off their super human hand strength and doing so damaged all 4 of my brake bleeders. Brake bleeders should have small "o" shaped holes, not oval holes or lines. If your brake bleeders do not have circular holes, throw em out and buy new ones. That there alone will prevent brake fluid from flowing properly and releasing air bubbles.

 

[brucecooner]

Thanks for the instructions. 

Sorry, this post got long and ranty. 
 

Today was a hard day with these stupid brakes.

I was so, so close to being done and driving again, then my entire hopefully final weekend of work just went out the window.

 

Just jump to the end if you want to try to help with my joyless, never ending quest to bleed a set of brakes.

 

 

I'm honestly about ready to sell this dang truck over the effing brakes. 

Every time I think I'm close to being done, something doesn't work and I have to undo a day or two's work and start over.

I've literally tried to bleed this thing two or three times now.

I got the closest I've come today, but then at the end it all quit working.

It's all because I'm doing things wrong, I know, it's just very frustrating because I read and follow all the instructions carefully and I still can't get the job done.

More below...

 

The rod on the latest booster was definitely too short. I could tell by holding it up to the original booster and the bad booster I bought last year.

I measured the cylinder bore depth, subtracted the flange, and it came to 0.962 inches.

The new booster was about a quarter inch short.  Given that the pedal has a mechanical advantage, I was probably losing a good deal of throw to the shortness.

It was difficult to gauge the rod depth on the new booster since it's in the truck, but it was easy to put nuts on the cylinder mounting bolts to that depth, so I put nuts on the two bolts, then held a straightedge across them to tell when the rod was just shy of the depth.

It was a little tedious, having to hold the rod while working the lock nut and turning the end out, but I actually enjoyed this step.

 

I had already pulled the new cylinder Saturday for the rod adjustment, and even though I had theoretically bench bled it before the last installation, I planned to bench bleed it again anyway.

I had already plugged the ports upon removing so I mounted it and began pressing the cylinder gently, using a spare rod that came with the booster.

I could get gushers in the front chamber (rear brakes), but even with just a quarter inch of fluid in the rear chamber (front brakes), I NEVER got a geyser of fluid to come up.

That coupled with the fact the snap ring in the bore looked slightly moist made me think it was bad. I took it back.

It was probably fine and I just don't know what the hell I'm doing, but Autozone didn't give me any flack and just replaced it on the spot.

 

There was a lot of casting flash around the inside and outside edges of the the chambers on the new cylinder so I taped over the ports, and held the cylinder upside down while I lightly filed the flashing off, until the edges were just smoothed.
I had held the cylinder upside down the whole time I was filing, and I blew some air into it before tipping it back rightside up.

Here's where I made my first mistake...

I untaped the ports and, because I thought I should clean it just to be sure but did not want brake cleaner in the ports, I put some brake cleaner on a shop towel and wiped the insides of the chambers.

I did not know it at the time, but I had just left a whole bunch of little bits of shop towel on the inside walls. I wouldn't discover this until later though.

Anyway, I mount it on the bench, and begin working the cylinder very gently. 

My setup allowed leverage and a great deal of control by using a screwdriver as a lever in the end of the spare booster rod.

I was extremely careful not to push the cylinder quickly nor very deep.

 

 

The instructions that came with the first new cylinder I bought said to do this for about fifteen minutes, until you see no more air bubbles coming out of the ports.

Here's where my mistake with the shop towel came back to bite me, as I could see little blue bits floating about in the chambers,

I stopped constantly to remove the little blue bits and curse my stupidity.

Anyway, it took more like an hour and fifteen minutes of steadily working the cylinder before the air bubbles quit appearing.

I wasn't sure if I should take that as a sign of making another mistake or a bad cylinder or what, but I was tired of messing with it and the wife wanted to go out so I called it a stopping point, carefully closed up the cylinder and put it in a gallon sized ziploc bag on a shelf between two things to hold it upright.

 

Today I went looking for speed bleeders. Apparently I'm going to be bleeding brakes every weekend for the rest of my life, so I figured they were a good idea.

I got a set for the fronts from Napa that looked like they've been opened but not used, and were the only set Napa had in the entire city of Phoenix.

It was easy enough to get them into the front calipers, and I was a little excited that bleeding the brakes might be easier next time I did it. (as if!)

 

Anyway, before putting the new master cylinder in I decided to check the state of my bleed job.  I mounted it back on the bench, got a couple more bits of shop towel out, and began working the cylinder and what do you know, more little air bubbles.  I was worried again I had effed something up, even though I had been super careful with the cylinder.

It only took a couple of minutes before the air bubbles stopped this time though, which I took as a good sign.

 

I used a right-sized plank against the seat bracket to hold the brake pedal forward, then put the cylinder on.  The plank popped out as I pushed on the rod but I seemed to have gotten the cylinder centered, so I tightened up the nuts on the cylinder and went through the struggle YET AGAIN of fighting the lines onto the ports.

 

So it was time to start bleeding.  I'm good and tired by this point, every few minutes I'm spilling brake fluid on something and just, tired, tired of working on brakes, tired of not having a vehicle I can enjoy, tired of hanging out in the driveway.

 

Anyway, my wife volunteers to work the brake pedal, I take up station at the passenger rear wheel and the bleeding starts going, pretty well actually.

The passenger rear goes solid with just a few presses, and my wife reports the pedal is stiffening a little bit. The pedal had never done that before.

The wrench of course pops off the bleeder as I'm closing it for the final time, popping off the hose and getting brake fluid everywhere, which sends me into another cursing tizzy as was sure the wrench popped off while the bleeder was open. We reset, press, open, close, release again a couple times but the fluid is still solid so I call the passenger side good.

 

I moved to the driver side rear, and this bleeder shoots out little bubbles for many many push-and-open-and-close cycles, but finally the bubbles all seem to be gone and I get a solid flow.

I clean up the fluid spilled on the axle from the wrench incident, cap the bleeders, and put the rear wheels back on.

 

I'm actually excited now, I'm thinking I might actually, finally be DONE working on brakes.

But no, this is where things went south in a hurry.

 

I lift the passenger side front, get the tubing and wrench ready. Since this one is now a speed bleeder though, I open it and leave it open.

My wife gets on the pedal, but no amount of pushing produces any fluid at the bleeder.

I make sure it's about a half turn open, and she's pressing, but still no flow.

In the cylinder, bubbles come out of the rear chamber ports (front brakes) with every  brake press.

On and on, no matter how many times we press the brake, there are bubbles in the chamber and no flow at the bleeder.

I can hear a slight gurgle from somewhere inside the cylinder with every push of the brake pedal, before the bubbles come out.

I become suspicious of the cylinder and feel underneath it, and there's a trail of brake fluid down the lower front of the booster.

I'm pretty sure it's leaking from the cylinder, so I begin another swearing tirade.

I'm defeated.  The pedal had actually stiffened after bleeding the rears. I was on the last step, and suddenly it's like the past two days have been for naught.

Continually swearing, upset that I've given so much of my life to these brakes, I removed the cylinder YET AGAIN, and find out that actually the bore is dry.

 

The supposed "leak" down the booster was just fluid that was splashing over the top of the open cylinder chamber and running down to the bottom and getting on the booster.

I can't do anything around this brake job without getting brake fluid all over my truck.  I'm so tired of wiping down, wetting rags, cleaning up brake fluid just, augh.

 

Anyway, so maybe the cylinder's good, I honestly don't know and I wouldn't even be able to tell.

I've been working on these brakes for literal months, and I still never seem to know enough to actually finish the job.

I was so close today, and then at the end, nope, final step sailed. 

I've followed all the instructions, carefully, and it never seems to get me to the finish line.

 

I pulled off the cylinder, again,  thinking it was bad, effectively undoing a whole weekend's worth of work. I probably pulled it for nothing.

Now I have to re-install the cylinder, again, and bleed all the brakes, again. This is probably the third or fourth time I've attempted to do this.

 

I'm so tired of failing at this.  I've come so far, but every time I try to bleed these brakes I fail in some new way.

Every time I try it, I have to discover some new thing about bleeding brakes I don't know.

I have learned any youtube video where a guy talks about how easy it is to bleed brakes is a filthy lie.  If the video starts with a guy talking about how easy it's going to be do his brakes, I just quit watching.  That's great dude that the universe smiles on your brake job but that ain't been my experience.

 

But yeah, I was done, I mean done with working on this thing forever.

I was so close, I thought I might get to finally enjoy my Jeep but NOPE. Nope nope nope.

I've probably effed something else up.

I hate looking at the thing now, it just reminds me of all the work and effort I've put into this thing to accomplish NOTHING.

I've been working for literal months, around sickness and weather, spending so many days and evenings crawling around this thing, and I still can't get it done.

The ONLY thing I've effectively done to this Jeep, in a year, is to replace the injectors.

I mostly enjoy working on it, or I did back when I started.

But months and months and it's still sitting in my driveway, gas in the tank slowly going bad, while I flail about underneath it.

And when I feel like I'm having no effect the work is just pure drudgery.

Maybe I'm just not mean to own this thing.

 

And I can't say that Jeeps suck. The Jeep is in pretty good shape. It's not that the truck or the brakes are poorly designed.

The problem is that I suck, I can't even get my stupid brakes to bleed.  I feel like such an idiot for just going on and on and on and on and on with this stupid job to get nowhere.  So many days and evenings I could have been doing something.

I think about how I could have just grabbed any random beat to hell Tacoma and I'd actually be out there enjoying the beautiful Arizona scenery. But there I am, crawling around under a Jeep because I bought what I wanted instead of what I needed.

At this point, I don't know if there's any point to me going on.  I'm this close to just posting it on bring a trailer, taking whatever I get, and letting some other fool give up all their weekends to this hunk of inert steel.  I'll just get the first beat to hell Tacoma I see and get back to enjoying my life.

 

Anyway, rant over. It's been a hard day.

 

------------------------------------------------------------------------------------------

Main question:

If your master cylinder (front brakes, in my case), doesn't seem to make pressure, and you see bubbles coming from the ports in the cylinder, what could that be a sign of?

 

One variable factor was the addition of speed bleeders to the mix.

Are there any issues that might be caused by a bad speed bleeder? Can they get "stuck" and refuse to allow fluid out.

I guess I should have cracked the one on the other side and seen if I got different results, but I was so upset when it seemed like the cylinder was leaking I was just angry and upset.  If I were remotely smart I would have jammed the old bleeder back in there and seen if that had any effect.

 

But even with dozens of presses, I never saw a single drop of fluid come out at the caliper. 

It looked like the cylinder just wasn't building any pressure to the front lines at all.

 

Bonus question. 

Can you get speed bleeders for the Dana 44 rear cylinders?

I googled extensively but couldn't find any sort of indicated part.

 

Also, big thanks to everyone who has helped. I have genuinely learned a lot.

 

 

 

[Salvagedcircuit]

Brake fluid gets everywhere when troubleshooting. I had to paint the entire right side of my engine compartment after I did the WJ brake upgrade. Diagnosing the braking situation was not an enjoyable process, but to me it sounds like your passenger front brake line is clogged or passenger side speed bleeder has failed. One of my speed bleeders failed because of over-tightening, making the hole into a line. Fluid did not flow well after this.

The passenger side front line runs from the back of the master cylinder block along the top back of the firewall, under the firewall seam and then down to the passenger front wheel. Every brake line in my '88 had failed when I was diagnosing my brakes, except this passenger front brake line. The armored brake line tends to hold dirt and debris close to the line and rot it out.

 

Originally, before I even tried the WJ booster + master upgrade, my  dual chamber MC was full of mud. I cleaned it out with paper towels and added new dot3 fluid, then pumped and pumped. The fluid came out brown on the driver side rear. After a half a quart, the fluid looked a little less brown, but the line exploded and started spewing out fluid from 2 pin holes in the brake line just about around the fuel filter area. At that point, my brother and I decided to replace every armored brake line on the vehicle. The passenger brake would flow fluid just fine, was not the armored kind and on inspection looked to be just fine, so I am still using it today. I used nicopp nickel-chrome line for all the replacement brake lines, you can find it online or at the auto parts store. It's nicopp CNC-325 or often labeled by the parent company, AGS.

 

I also had what I thought was a "leak" down the booster front, but it was from me accidentally not holding the MC level and spilling some onto the surface of the booster. Unfortunately, some of the fluid entered the front of the booster and that booster was no longer fit for use (brake fluid eats rubber).

 

I understand your pain and shear frustration with your vehicle. I've been working on my comanche for a year straight and it just finally passed inspection. It was a lot of work and stupid little things that added up to a lot of time and headaches. Hopefully your headaches should be over soon.

 

I am by no means a master at doing this, but in my opinion, your bleeder may have failed or your front brake line is clogged. I wish you the best of luck man! I know the pain all too well.