Brake Problems

#1

Anyone know the difference in the brake master cylinder for the ATE brakes and the Girling brakes? I am still chasing brake problems on my car and noticed that there are two different master cylinders and I am sure I got the ATE one instead of the one for the girling (made by lucus). Next anyone know how to test a brake vaccum booster? Anyone ever put a pressure gauge on the brakes and check the pressure per the Bentley? And now for testing the ABS pump? Any ideas.

Brakes just don’t seem to stop and sometimes seem to go to the floor and sometimes are very hard. I disabled the ABS and that seemed to help the feel but if I pump once I got a very hard pedal.

Thanks for any help.

Michael O.

#2

If the brakes tend to go to the floor it indicates that the master cylinder is acting up. Ask Damion if he got his problem fixed with a new master cyinder and I’ve had the same positive results in changing out cylinders.

Regareds, Robert Patton

#3

I asked Zigglet and he said you need to replace the master with the same brand you took out.

#4

I have a new master cylinder but I think I put on an ATE. It looked just like the one I took off. I was wondering if there was any functional difference in the two. Maybe a different bore size.

Michael O.

#5

A different bore size would affect pedal effort, but it would not cause the pedal to go to the floor sometimes and feel hard other times. That sort of behavior sounds more like a bad master cylinder.

The usual failure of a brake booster is failure of the diaphram, which results in a hard pedal and poor braking performance. But a problem with the valve internal to the booster or a fault in the vacuum line or check valve could result in good brakes and low pedal effort sometimes and a hard pedal and poor brakes at other times. Disconnecting and plugging the vacuum line will let you see how the brakes behave with no boost and that can be compared to what’s happening now.

#6

Jim - I agree. I know several folks in our region who do not even have the brake booster hooked up (i.e., have the vacuum lines from the intake removed). Every master cylinder that I have had fail resulted in leaking - usually onto the floor (and shoes!) This problem sounds like a bad/clogged up proportioning valve, a sticky piston in one of the calipers, etc. The brake hydraulics are pretty simple, although the ABS circuit complicates it somewhat. Have the calipers been rebuilt - lines checked, etc? As far as the master cylinder manufacturer is concerned, I believe a call to a dealer or Zygmunt, Bimmerworld, etc., should be able to sort that issue out.
Ed

#7

Maybe saying the pedal goes to the floor is too harsh. When the ABS was hooked up I felt like I had my foot on the floor and no stop but that may have just been the ABS not letting the car stop.

All the calipers have been rebuilt. I have removed the proportioning device and took it apart and cleaned it. The brakes seemed better without the ABS on and most of the problem may have just been the slow to react ABS. I did try to pump the brakes once and on the second application of the brakes got a very hard pedal. I am going to try an test the pressure at the rear calipers and make sure it is within spec.

Keep the ideas comming.

Michael O.

#8

Another question for the group, Re: testing the ABS pump. After Rockingham, I’m not too confident in my ABS and will probably just disable it, but I’d like to hear if there’s a good way of testing. Can it be disassembled to clean?