Help with brakes

[jerseyjeep2003]

AAARRRGGHH, Master cylinder rebuilt, Airpack & slave cylinder rebuilt, added remote reservoir, and pressure bled system. Nothing, nada, nunya, pedal still goes to the floor. I had massive amounts of air at the wheel cylinders, but finally got straight fluid under pressure. But still no pedal. OK, thought about bench bleeding the master, but, it should have been OK since I bled it at the air pack. I then discovered a missing copper washer at the output of the master cylinder. Thought that was the problem, NOPE!! I am at wits end here. Should I just continue to bleed the system, or put on a different master cylinder I have ( it was oozing fluid even though it was new)? Any thoughts from those smarter than I?

I had another post on rebuilding my air pack, but it seems to have gone dead, so I'm making a fresh post for some thoughts.

 

[jtrojan715]

does the pedal pump up then bleed down or just nothing? might be the master. any leeks in the system?

 

[jerseyjeep2003]

After first bleed, pedal kind of was at the halfway point, but then on third pump went to floor...no pressure at all. I could hear the fluid moving, which meant more air. So, I started checking and discovered the missing copper washer on the line out of the MC. I replaced it with a new washer and rebled the system starting at the airpack then the RR wheel, LR wheel, RF wheel and the LF wheel. I did use a pressure bleeder with minimal pressure, just enough to push the fluid. Got clear fluid, some air then clear fluid again on each bleeder. I didn't see any leaks anywhere.

 

[jtrojan715]

sounds to me like the seals in the master are shot and i wouldnt use the one that ozzes eather. id try to find a rebuild kit and reseal it. im by far no expert but those are my thoughts

ohh didnt se that the master was just rebuilt. did a seal get niched. other then that i dont know

 

[jerseyjeep2003]

I rebuilt the MC and the airpack at the same time. The original problem was a leaky airpack letting air into the fluid side of the system and brake fluid into the air side of the pack. I am baffled as everything associated has been rebuilt.

 

[Clay James]

If there's no leaks it has to be air in the system. This sounds similar to what my buddy's deuce was doing. It turned out to be tons and tons of air coming out of the front left wheel cylinder so it was in the line going from the front to the air pack. It would shoot out lots of air bubbles then go back to fluid, kept bleeding and got a bunch more air bubbles. This went on for a long time and I bled a lot of fluid, but finally didn't get anymore air and there was pressure on the pedal. On this truck I blew that line out with compressed air so it was completely empty. On my truck I didn't and I didn't get all that air when I was bleeding it.

 

[DeucesWild11]

Did you hone the cylinders during the rebuilds? I had been loosing pressure after the airpack rebuild so I went for the MC. Once I rebuilt the MC it was perfect. If you are not loosing fluid I would suspect an internal problem in the MC. I was not loosing any fluid anywhere but was loosing pedal pressure. Either that or air is getting in the system somewhere.. If you can't find air getting in anywhere or a leak then I would go for a new MC as they are not that expensive..

 

[jerseyjeep2003]

Yeah, cylinders were honed. I took about .003/side, the cups still fit snug, so I don't think I took too much out of them. Going to try and bleed the snot out of everything before I start at square one.

 

[jerseyjeep2003]

Before I started the project the MC had leaked itself bone dry on my way home from work one night. I limped it home by going slow and downshifting before pumping what little braking power I had left.

 

[Motorcar]

The fact that you had pedal after bleeding then all the sudden it dropped to the floor and you could hear fluid pushing, leads me to lean towards the master bypassing on an inner seal failure. I wish there was a cheaper solution than install a "known good" master and bleed at air pack to see if the problem has been eliminated.

 

[DeucesWild11]

try bleeding one more time starting with the Airpack and see if that works, then I would try a new MC..

 

[phil2968]

Have you built a power bleeder yet? How are you bleeding the system? Hook up a power bleeder and a hose to the bleeder screw to catch the fluid in to be reused. Start at the airpark then move on out to the wheels.

 

[dozer1]

I believe he said he power bled the heck out of it. Impossible to know for sure from here, but I would chuck the MC and put a new one on. I have heard they have some kind of an internal bypass checkvalve that can stick open and cause grief. Can anyone verify this?? That would make it do what you say it is doing.

 

[rlwm211]

It sounds to me like internal leakage.

The only way the pedal can go to the floor and have no effect is if it is bypassing in the master.

As long as it is not escaping the Airpack you will eventually build up a pedal if the master is good.

Even if the brake fluid is bypassing internally in the airpack it will not create the situation where the brake pedal does not build some pressure. Once the airpack is full the pressure will build unless it is leaking onto the ground from the airpack and according to the OP it is not.

 

[jerseyjeep2003]

OK, I bled everything AGAIN. Bed at the line fittings and bleeder valves without having started the truck, had gotten the beginnings of a pedal (about 1/3 up from the floor) not great, but felt like I might have it this time. So I started the truck and built air pressure, and BOOM to the floor, nothing. Went back and checked the lines and bleeder at the air pack and got air again. So I just finished pulling the airpack and the air side is nice and dry as is the air valving on the slave side. Air has to be pushing past the valve chamber is all I can figure. Yes all of the cylinders and seals are clean and no pits. Going to double check my assembly to make sure I didn't do something stupid. Then recheck the master cylinder, I just rebuilt that also. I have seen several different master cylinders, could each one have it's own kit, and I got the wrong kit for mine? All of the replacement parts appeared the same.

When I would "pump" the pedal (after disconnecting the pressure bleeder) I have bubbling back into the remote reservoir. Sorry about being long, just trying to hit the details as much as I can.

I even called Jimo at Caveman Trucks as he is not too far from me (45 minutes), he said, yeah they can be a real pain, and he spent quite a bit of time trying to get one right. And recommended switching to a hydroboost from a large civvie truck.

Heading back out to the shop to analyze the situation before reassembly. I'll check back for comments/suggestions.

 

[jerseyjeep2003]

I believe he said he power bled the heck out of it. Impossible to know for sure from here, but I would chuck the MC and put a new one on. I have heard they have some kind of an internal bypass checkvalve that can stick open and cause grief. Can anyone verify this?? That would make it do what you say it is doing.

I am leaning in that direction. I do have an emergency spare MC. It was oozing fluid, but worked when I switched it out. It was new less than a year ago, so it may give me an indcation if it is the "rebuilt" MC. Yes there is an internal valve at the end of the piston/seal assembly.

 

[jerseyjeep2003]

WOW....I would have never figured this to be the problem. The vent tube by the air cleaner that had what looks like a brass plug, is actually an orifice plug. The tiny hole in it was completely plugged with dirt, causing any air venting from the air pack to not vent and over-pressurize the whole system, and force air back into the slave cylinder. I removed the plug and replaced it with a sintered brass filter and was able to bleed the system normally. Now I have brakes again, but they need adjusted. SO, if ya have any issues in the air system....check the vent line and the final fitting.

 

[jtrojan715]

WOW never would have thought of that

 

[dozer1]

Good job on the diagnosis! Going to have to remember that one.

 

[rlwm211]

When I bleed brakes I do not use the vent line until I am done. I also use the time tested method of using a hose on the bleeder with the other end in a bottle with BFS in it with the end under the surface and I pump the pedal a couple of times and then add more to the master.

This is the one fact that you need to know. The master contains enough extra brake fluid to push the pedal all the way to the floor a maximum of three times.

If you think you have a brake line leak while on the road, this will limit how many times you can pump the pedal before you are out of BFS in the resevoir.

A remote resevoir will increase this of course.