RXRodger

iTrader: (2)

the next time I hit the brakes to floor again but with a pump is solid. When the pedal becomes firm I can stop at the limit and I don't lose any pedal which I am assuming means the master cylinder is probably ok. I have literally spent hours on this forum trying to find information on this problem.

Here is what I have learned after my hours of search and messing with the car.

1. Apparently the proportioning valve for the brakes is built into the ABS unit.
2. As stated above it seems the master cylinder is ok due to the fact once I pump the brakes and the fronts engage I don't lose pedal.
3. When it goes almost to the floor, the only brakes that engage are the rears, the fronts don't seem to catch at all. When I pump, the fronts come on hard as you would expect.
4. If I apply the brakes and the fronts engage, if I let up a little but not all the way off the pedal and then reapply it almost always goes almost to the floor and only the rears seem to catch. But if I pump a couple of times and apply the brakes, the pedal is high and the fronts engage as expected and no pedal fade.
5. Pulling the ABS relays does nothing to help the situation.
6. I have bled the brakes multiple times, there is no air in the system.
7. The car was rescued from going to the salvage yard because it had taken a hard hit on the left rear and broke all the control arms and busted the brake line on this caliper and all the fluid drained out over the time it sat. I replaced the brake line and bled multiple times. Since then all wheels bled multiple times.

I am assuming at this point wherever the proportioning valve is in the ABS unit, that is where my issue is. But, I am looking for anyone that has encountered this issue and what they ended up finding.

t2d2

iTrader: (8)

Have you pulled ABS codes, by any chance? (OBDI is: jump Tc & E1, count the blinks on the ABS light. '96 you would probably just plug in a code reader.)

RXRodger

iTrader: (2)

The ABS light is not on, so am I correct in assuming there are no ABS codes? I haven't tried to flash them, will do that and see what it says.

I drove the car today, now I am thinking it might be in the master cylinder. Here is what I did today. Every time I needed to brake I slammed on the brakes. I was thinking if the v ring type seals were hard when you press on the brake hard it would force them to seal due to the quick high pressure. The brakes worked every time when I did that, always a full pedal. It only would be an issue when I would apply brakes lightly which then I would pump and they would work fine. Anyway, just a theory, still could be in the ABS unit, but now I see a possibility of how it could be the master cylinder. Will update what I find out later.

t2d2

iTrader: (8)

I would assume that's correct, but file it under the "couldn't hurt to check" category.

logix7

keep us posted- im having a similar issue where my pedal slowly gets soft at red lights. havent bothered to dig in to it yet

vipsoarer

Just because you get pressure after a pump doesn't mean the seals in the master aren't bad...most likely that is your culprit. On the 4 cars I've had either a sinking pedal or it takes a couple pumps to build pressure, the end fix was always the master cyl leaking internally and bypassing itself. Only once the rear seal had fluid was dripping down the firewall in the cabin. It can be hard to see these leaks because of the pads on the firewall and the thick plastic bottom carpet. These cars are old and brakes are pretty important. Cheap insurance especially with what you said in your recent test of hard pedal pressing.

Logix7 - yours sounds spot on like your master is dying as well.

good luck fellas

RXRodger

iTrader: (2)

Yep, the more I drive it and think about it, it just about has to be the master cylinder. I will try to get it replaced this weekend and update what I find out.

Blkexcoupe

iTrader: (8)

Your problem sounds like the master cylinder. Most problems with the pedal being soft is related to the MC and most problems related to a hard pedal is the brake booster.

I've heard of master cylinders going bad because of the brake bleeding procedure we use. The trapped debris gets into the back of the MC and under normal driving we never extend the pedal enough to push that debris out. During bleeding we fully extend the MC and it forces the debris out causing the seals to fail. I don't know how true this is, but it kind of makes sense. I noticed my MC started leaking where the MC meets the brake booster after the last time I bled my brakes. Luckily, the MC is rebuild-able with OEM parts for relatively cheap.

Rebuild kit: 04493-30241
MC Gasket: 47275-12020
Brake Booster Gasket: 44785-14020

RXRodger

iTrader: (2)

So I should have researched this a little closer on parts. I didn't order a master cylinder for this 96 model thinking I would use one from my parts stash for the race car which is a 92 model. The 92 has the 3 bolt flange, the 96 has the 2 bolt. So, looks like next week before I can do this job.

Update: Replaced the master cylinder, good to go now. However, the level sensor apparently does not work on the Raybestos "Professional Grade" master cylinder. That really irks me. It's not that it has be replaced its the time, the brake fluid, etc that irritates me to have to do again.