Problematic Brake Upgrade: The Saga Continues

[Salvagedcircuit]

Problem:

Finally completed the WJ dual diaphragm brake upgrade. My front disc brakes don't seem to be doing anything. Bleeding does not yield stiff pedal.

 

Symptoms:

After a quick 40mph test on a closed paved road, Rear drums grab and get warm. They get to about 210f with a thermal gun. Front brakes barely hit 90f, so they don't seem to be doing anything.

 

Observations:
no brake fluid leaking anywhere. No fluid leaks from front calipers, rear drums, rear axles, master, or prop valve. When bleeding entire vehicle, brake fluid flows easily from all brake fittings.

 

Work Done:

1. Removed original master, booster and distribution block
2. removed prop valve under bed
3. installed new WJ Cardone 5C-473163 booster + Raybestos master MC390511 combo.
4. master cylinder properly bench bled. 1in travel on shaft at most, according to cardone. Pumped for 15min. no air bubbles.
5. master properly aligned to booster outside vehicle and then installed into comanche.
6. new DOT3 fluid used
7. new wilwood 260-13190 prop valve
8. new nickel chrome brake line to the rear axle drum brakes
9. removed all old brake lines to the back
10. new fittings.
11. old front passenger brake line
12. old front driver brake line
13. new rubber brake lines on all wheels
14. old passenger front caliper
15. new driver front caliper
16. new passenger and driver caliper brake pads
17. disk brake fittings in up position, not down, so calipers should be installed correctly.
18. bled entire vehicle 8 times. No more air bubbles last 4 times bled.
19. bleeding does not yield a stiff pedal.
20. bled vehicle in proper passenger rear, driver rear, passenger front, driver front fashion.
21. bled system with prop valve in middle and then again at 30%, no change.
22. I bleed vehicle with engine off. When engine on, pedal becomes soft.
23. Engine pulling vacuum well, I removed many vacuum leaks, but there may be some I missed.

 

I called wilwood on 10/31 about the brake problem I have. the technician mentioned that I need a 10lb residual pressure valve for rears. This would be installed right after the brake line out of the prop valve. He mentioned that many car companies implemented a 10psi pressure valve into the master cylinder distribution blocks on older vehicles. He mentioned this helps resolve the rear drums locking up before the fronts. While this may help resolve that issue, I don't think it's going to solve my soft pedal problem and the front discs not doing much.

 

I'm really drawing at straws here trying to determine the source of the problem. I've been through 3 whole 16oz bottles of dot3 fluid and I cannot get usable brakes. I'm about ready to hand it off to a shop, but I have a feeling they will not be able to solve the problem either.

 

My first inkling is to make new driver and passenger brake lines, but I have a feeling that will not solve the issue. If anyone has any input, that would be great. Thanks!

[ghetdjc320]

Any chance you have the front and rear outputs reversed on the MC? 

[gogmorgo]

X2, that was my first thought, reversed front/rear lines, either at the master cylinder or on the prop valve.
While I’m not really in a position to argue with Willwood, I don’t think you’ve got accurate information there. The residual valve on a drum brake is used to hold pressure in the brake line after you release the brake. The reason for this is to stop the return springs on the brake shoes from pulling them all the way back away from the drum. If you don’t have a residual pressure valve, your rear brakes will engage more slowly, as if they’re out of adjustment. I think there’s some confusion with the effect a residual pressure valve has on a disc brake system, where it’s used to deal with weirdnesses that come up when you mount the master cylinder lower than the callipers (very unusual but it happens), one of which is a spongy pedal due to gravity pulling the brake fluid out of the callipers, lightly sucking the pistons back in. I don’t think your issue is due to a lack of a residual valve, which in my understanding is there to speed up brake applications.

On the other hand, the front callipers require a much larger volume of fluid to expand the pistons than the rear wheel cylinders do. In the case of the WJ, the front callipers have two pistons the same size as the single rear piston, meaning twice the volume.  If you’re pushing a huge amount of fluid into the rear brakes and only a small amount into the fronts, the rears are going to grab hard and the fronts aren’t going to do much at all, and I imagine the brake pedal would seem a little odd. 
One other valve that a disc/drum setup usually needs is a metering valve for the front brakes. This is used to slow down the pressure buildup in the disc brakes to account for the time needed to build up pressure to overcome the return springs on the drums, so they both apply at the same time. Generally this is included in a factory distribution block or proportion valve. But again I don’t think one missing from the system would cause your issue, considering it’s also there to slow down front brake application relative to the rear brakes. The only reason I bring it up is in case the prop valve you’re using has one built in that either is way too aggressive or malfunctioning somehow, and blocking more flow to the front brakes than it should for longer than it should. 

[cruiser54]

Did you eliminate the distro block in the engine bay?

 

What about the valve in the rear? 

[Salvagedcircuit]

Just edited the original post. distribution block and rear prop valve removed.

 

It is possible that I connected the two lines from the master cylinder to the prop valve in the reverse manner. There was no documentation with the raybestos master cylinder stating what each line was for.

I have to double check my photos.

 

Thanks for all the input guys.

[ghetdjc320]

9 minutes ago, commissioneranthony said:

Just edited the original post. distribution block and rear prop valve removed.

 

It is possible that I connected the two lines from the master cylinder to the prop valve in the reverse manner. There was no documentation with the raybestos master cylinder stating what each line was for.

I have to double check my photos.

 

Thanks for all the input guys.

That’s a good possibility. Keep in mind too that there is some confusion about what an actual proportioning valve is and how it works. From what I’ve been able to gather the Wilwood is not a true proportioning valve unlike say the oem ZJ/XJ/YJ valve. A true “proportioning” valve should maintain equal brake line psi percentages. In other words, say 60/40% split regardless of input pressure. The Wilwood adjustment valve caps the max pressure for the regulated side (the rear) so it’s not truly maintaining proportional fluid pressure at all times. At least, that’s what Wilwood described a few years back. That’s why it has an adjuster on it. 

[Salvagedcircuit]

I guessed that the front of the unit is for the front and the rear is for the back. Again, Raybestos makes no effort to provide any documentation about the item. They don't even list the part on their website. I'm calling their tech support now but I am conveniently getting an answering machine.

[ghetdjc320]

I believe that’s backwards. The larger outlet is usually the front. It’s the port closest to the front of the bore

[Salvagedcircuit]

6 minutes ago, ghetdjc320 said:

I believe that’s backwards. The larger outlet is usually the front. It’s the port closest to the front of the bore

I'm looking back through the WJ service manual to see if I can straighten this out. Thanks for all the input. I really, really, really appreciate it. Seriously, Thanks.

I'm hoping this is the solution.

[Minuit]

I'm at least 90% sure that the back of the unit is for the front brakes.

[89 MJ]

Same with the others, usually the rear of the reservoir is for the front brakes. 

[Salvagedcircuit]

Here's a snapshot from the WJ service manual.

 

Quote

The primary piston supplies hydraulic pressure to the front brakes.

The secondary piston supplies hydraulic pressure to the rear brakes.

 

Here's the master cylinder properly labeled.

Well, That's all folks

 

Is there anyway to know if I damaged the master cylinder or prop valve by having the lines reversed? I ran the comanche 5 times at 40mph for brake testing.

 

 

 

 

 

[ghetdjc320]

1 hour ago, commissioneranthony said:

Here's a snapshot from the WJ service manual.

 

 

Here's the master cylinder properly labeled.

Well, That's all folks

 

Is there anyway to know if I damaged the master cylinder or prop valve by having the lines reversed? I ran the comanche 5 times at 40mph for brake testing.

 

 

 

 

 

Should be fine but you’ll need to re-bleed the system. 

[Salvagedcircuit]

Thanks again for all of the help guys. I swapped the lines and re-bled every wheel (rear passenger, rear driver, passenger, driver). I now have brakes but the pedal seems very weak.

 

I removed the rear drums and inspected the drum cylinders and there were no signs of brake fluid leaking anywhere on the drum backing plate assembly.

I reinstalled the drums and adjusted the rear drums again, following advice on how to properly adjust the star-adjusters. The pedal still feels soft up until the last, say, 1/8 of the travel length.

My wilwood proportional valve is set on 5 turns, about 50%.

I have a new brake line in the back and old brake lines in the driver front and passenger front.

I notice there is a large sucking sound whenever I press the brake pedal to the floor.

I then disconnected the vacuum from the booster and plugged the hose. If I do not plug the hose, the engine revs pretty high. My brake pedal now feels pretty stiff. However, when I use the brakes with the vacuum disconnected from the booster, they barely work. It takes a while to stop from accelerating to 5mph. It does indeed stop and it is not just rolling resistance.

I plugged the vacuum line back into the vacuum booster and the pedal is soft again until the last 1/8 of travel. However, the brakes work a lot better. I put my rear tires on the lawn and my two front tires on the pavement. I was able to do a burnout while the front brakes held the vehicle from going forward.

I conducted another burnout test with all front and rear wheels on the pavement and the front brakes hold the vehicle in place while I spin out the rear tires.

It just seems incredibly strange that 7/8 of the pedal travel feels incredibly soft.

Am I not getting enough vacuum to the booster? My vacuum gauge is measuring 15in-mg when the engine is idling (~400rpm). I connected the gauge with a T as stated in the 01 WJ manual.

I did my very best to baby the master cylinder during bench bleeding. I did not mishandle it in anyway. I did not push the shaft more than 3/4in when bleeding for fear of flipping seals. I triple checked the master and booster alignment so they are definitely aligned properly.

 

I am at a loss of words to why this does not work.

If anyone has any advice, I would greatly appreciate it. Thanks!

[Salvagedcircuit]

An update on this. I checked my driver front caliper and I noticed the 3 month old autozone caliper shifted on me. I do not know if either I did not torque the slide pins enough, or maybe I forgot to push the caliper in all the way. I have never had this happen to me on any vehicle I've worked on. 

I am also investigating the rear driver side drum cylinder to see if its leaking internally and lastly I will double check the booster push rod length.

 

I originally decided to leave the booster rod length stock as there was no documentation from jeep on adjustment in the WJ manual and the cardone technical asce technician did not mention the process. The photos included show the booster length just before I installed it. This is the length shipped by cardone. The adjustment nut is fully seated on the push rod shaft. I did not make any adjustments.

I will be calling cardone again tomorrow and re-reading the lexus booster rod length adjustment process cruiser54 mentioned.

This could be the reason why I am experiencing a soft pedal for 7/8 of the throw and it then gets hard the last 1/8 of the throw.

[cruiser54]

Cardone will likely be no help.

 

I have used clay to measure and it can be done with a caliper. 

[Salvagedcircuit]

I am going to address my glaring issues with the driver side brakes and then inspect the booster. Worst case, I will grab some clay or mounting putty and take a measurement. Thanks again cruiser54 for the input.