Front brakes won't bleed. Help me my friends!

[MishapMaggie]

I'm sure this has been covered on many threads but none that I've been able to dig into, as a newbie, that have led me down to a path of success. 

 

Please tolerate me, as I'm as old as my jeep, and I'm just a damned partsmen whom is clearly over her head these days! 

 

Background :

 

My '86, 2.5, 2WD has been sitting in a field since 2005. It was then towed beside a garage that eventually caught fire...tons of melty issues, all have been worked out but this. I bought "Darnit Daisy" in hopes to relieve myself from a JK fuel mileage of 20L/100 (outfitted for overlanding) daily driver that isn't so happy as a daily. Canadian here. :)

 

Issue:

. I replaced as much as I could... master, calipers, rear cylinders, new friction, lines from the master to the directional valve under the master. I haven't done the other lines as they cracked fine when replacing the brake hoses and rear cylinders. No leaks. But the front kinda seems to keep pushing air? No leaks visible on the booster area either. 

 

I bench bled the master so many times, I've had hands on deck to assist me with bleeding too. The rears are a-ok while bleeding, pumping builds pressure, pedal drops after the cracking, no air in the bleeder tube or in that side of the master, the rears are happy. 

 

Once we get to the front, there's no pressure building on the pedal, and no pedal drop on "hold". The front brake portion of the master foams with air. Still, there are no visible leaks anywhere. 

 

100% factory system, from the parts diagrams it all looks bueno. The rear proportioning valve is hanging out and dry, doing its thing and probably having a drink toasting our suffrage.

 

I think I understand the brake bleeding process, passenger rear, driver rear, passenger front, driver front, ignition on, crack front, brake light, bleed rear, close front, go back to passenger rear, do it again

We can't get past the passenger front.

 

Where do I start diagnosing from here? I'm not looking to get fancy with swaps, deletes or anything that isn't warranted past stock if I don't have to. It's fishing season :)

 

Thank you for any input you may have, I greatly appreciate it. I'm a bit worn on patience with this 'ol gal, and I'd like to see more road and less garage floor these days. I'm pooped trying to sort it out. 

 

 

-Rhonda 

[75sv1]

Did you change the rubber brake lines? They sometime delaminate internally. Acts as a one way valve. My neighbor just went through this with a KIA SUV he was working on. 

[mjeff87]

Make sure your new calipers are on the right sides.  The bleeders have to be at the top, not the bottom.

[MishapMaggie]

1 hour ago, mjeff87 said:

Make sure your new calipers are on the right sides.  The bleeders have to be at the top, not the bottom.

 

 

They are on the correct sides, bleeders up. I was hoping I'd had a "doh!" moment...but nope they're good.

[Eagle]

20 hours ago, MishapMaggie said:

Once we get to the front, there's no pressure building on the pedal, and no pedal drop on "hold". The front brake portion of the master foams with air. Still, there are no visible leaks anywhere. 

 

 

You are seeing air foam IN the master cylinder, or at the caliper?

 

Actually, I'm not sure it matters. Obviously, a hydraulic brake system is supposed to be a closed system, except when you open the master cylinder to add fluid. If you're getting air into master while bleeding, that suggests to me that the master is defective.

 

How are you bleeding? I have seen a lot of inexperienced (and some experienced) do-it-yourselfers who pump the peddle rapidly and vigorously between bleeds to refill the line after each bleed cycle. That's wrong. Rapid pumping creates air bubbles (foam). When bleeding, peddle movements should be slow, and after each bleed cycle it only needs one or two peddle cycles to replace what was pushed out of the line. Pumping the peddle rapidly a dozen time doesn't help, and can cause issues.

[gogmorgo]

I think you may be over complicating the bleed sequence and doing it a little out of order. 
Start by cracking the front bleeder, then bleed the rears. Close the front bleeder, bleed the rears again, then the fronts. 
If you don’t have the rear brakes fully bled before trying to bleed the fronts the emergency bypass will do strange things.

 

Just to confirm, this is the correct orientation of the weight/height sensing proportioning valve:

 

If you don’t have the rod going down to the diff, you can tie the bar up in more or less that position, pointing at the passenger side and a little above horizontal.

It’s not unusual to find the two flipped over centre with the rod sideways and the flat bar pointing downwards, or the rod might be missing completely with the flat bar dangling. If that’s the case you won’t get much braking power at all from the rears, and it may also affect bleeding.

 

As Eagle points out, light but steady pressure is best for bleeding. Think just enough pressure to hold an automatic in place while you’re in gear on flat ground. Hold pressure on the pedal, crack the bleeder, let the pedal sink while maintaining the pressure on it, and close the bleeder again just before the pedal hits the floor. I like to watch the air bubbles coming out of the bleeder and close it while they’re still moving. 
When I’ve been on my own without access to a vacuum bleeder I’ll make sure to use a hose with a tight fit on the bleeder and run a few inches straight up off of it, possibly with a couple loops before going into the container. I’ll leave the bleeder open and pump the pedal slowly a bunch until there’s clean fluid. Bonus if your hose reaches far enough you can see the bubbles in it. This doesn’t get a perfect bleed, but it’s generally going to be good enough to get around until you can do it properly.

Also critical, don’t let the master cylinder drop too low while bleeding. If you suck air in, you need to start all over again. 
 

 

Failing all this, there’s another recent thread about brake bleeding. Among other issues, the master cylinder and booster had been replaced and the push rod hadn’t been adjusted correctly out of the box or something. 
 

Hopefully you’re not too close to the any of the fires, and your air isn’t too bad. Doing anything outside in the smoke is not a good time.

[MishapMaggie]

I greatly appreciate the help, I'm pretty easy on the pedal pushing. I've been in charge of that in all our projects since I could reach the pedals and have fond memories of my dad losing his mind for being too aggressive with the pumping on his fairlane lol. Never did that again.. 

I'm getting back to it tonight, I had to get my house b*@ch duties done last night. 

 

Quite a few people have mentioned a bad master, here and in my trade (but I work with Toyota techs who are younger than me, so they are confused by the ol jeep on many things, you should have seen their faces when I explained TBI.) I respect your guy's opinions greatly. I'll confirm the load valve position and try again and try the bleeding process you suggested. I found a booster rod measuring tool in the tool room, when I asked if I could borrow it my foreman said "What is that? Sure, never used it". So I'll check that too

 

I'm just losing my patience I think, the whole engine Diag was enough for me, but I'm close...so I have to keep trucking! 

 

I'm close enough to the smoke it's annoying, especially with the heat but it's cooling off and raining soon, so if all goes well it won't be too painful! Yay Alberta! Thank you all so much for your kindness :) 

I will report back! 

[MishapMaggie]

Thank you all for the help, after a long night of trying to bleed the system on Tuesday, confirming your suggestions, and getting the same issue over and over, I got a new master today and installed it.

My Comanche has brakes for the first time in a long time! 

 

Thank you so much for the suggestions!