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View Full Version : Braking Issue - Sticks - Help Troubleshoot


duaux
11-15-2011, 10:29 AM
For those who are familiar with brakes and their inner workings...
---------------

My Problem:
When I brake "hard", the pedal sticks to the floor.
I have to pump (2-3x) for it to come back up.
"Regular" braking works fine... e.g., Stopping is not an issue, is only when I firm it up at that "last bit" for it to "lock" and the pedal sticks.

Bentley Says:
1. Air in the brake lines
2. Bad master cylinder

What I have checked and done:
1. No leaks that I know off...
2. Bleed my brakes "again" (full flush)

Background info:
1. I recently just replaced both my Clutch Master & Slave Cylinders as my clutch was "stuck" to the floor... (that is another story). My clutch now works 100% fine now.
2. Full brake and clutch fluid flush

So I have flushed the brakes "twice" now, once after installing the Clutch Master & Slave Cylinder, and once since I started getting this issue which was approximately 1 week after the install.

I just want to have some reasonable comfort that it is the Brake Master Cylinder before I spend the TIME and the MONEY to replace it. Braking seems to be "working".

Any pointers appreciated.

Thanks!

E30M42cab
11-15-2011, 12:03 PM
I'd bet its a bad master cylinder.

Do your brakes release properly?

duaux
11-15-2011, 12:16 PM
Thanks for responding E30M42cab.

*Are you referring to the actual brake calipers themselves release?
I believe they are... but I guess I should go and confirm that as well.

Only hard thing is, I will have to put the car on jack stands, and have someone press the brakes hard enough for it to stick/lock.

As noted, it only sticks when I brake hard. e.g. Press the brakes all the way.

Other note:
Not sure if this is useful additional info, but I did replace all 4 brake caliper bleed valves since the old ones were rusted out and filled with crap. Those who bleed their brakes probably know what I am talking about.

dcramer
11-15-2011, 02:20 PM
Yes, actual brake calipers.


Have someone turn the wheels while you brake. Then release the pedal see if the calipers release.

duaux
11-15-2011, 03:28 PM
Good idea...
Thanks, I will give that a try. Hopefully when I get some time this week.

dcramer
11-15-2011, 03:31 PM
FWIW, I have other problems with my brakes and I happen to have one rebuilt caliper on the car and the other 3 are original. The rubber bushings on the 3 original ones are very tight, the rebuilt one slides properly. I've ordered new bushings for the other 3 calipers as I'm sure the 13 year old bushings are getting old and hard. The bushings have to slide properly for everything to work.

duaux
11-15-2011, 07:43 PM
Hey dcramer,

I am actually thinking of rebuilding the calipers or buying some reman one's.

Which bushings are you referring to?
1) Piston seals

OR

2) Guide bushings


http://bmwfans.info/parts/catalog/E30/4-doors/USA/325e-M20/LHD/M/1987/january/browse/brakes/front_wheel_brake_brake_pad_sensor/
http://bmwfans.info/parts/catalog/E30/4-doors/USA/325e-M20/LHD/M/1987/january/browse/brakes/rear_wheel_brake_brake_pad_sensor/

duaux
11-15-2011, 07:53 PM
OK, I just realized that there are two types of front brakes... I will need to go and check mine to confirm.

GIRLING and ATE

dcramer
11-15-2011, 08:03 PM
Well it all has to work properly, but the guide bushings are what I was referring to. I think they are often overlooked.

Before you buy the kits you should make sure the pistons are good. About the cheapest way to get pistons is to get reman calipers. Unfortunately this means taking them off the car and pulling them apart.

Dave

duaux
11-16-2011, 08:53 AM
I C. Good advice dcramer.

Thanks.

FWIW: I got one quote from a TDOT shop (for those who may be interested)

Midwest Caliper (Rebuild)
"Hi, what type of calipers do you have on the front, are they Girling or ATE. We have have them both in stock and they are $55 each for the fronts and $55 for the rears. It would be they same cost to rebuild your calipers.
Thanks for the inquiry"

dcramer
11-16-2011, 08:55 AM
For that price don't bother rebuilding them, especially if they include new bushings which mine did.

duaux
11-16-2011, 09:34 AM
I see your point...

But I also have to take the cost of the "possible" Master Brake Cylinder replacement into consideration as well.


:::Rambling:::

Parts only:
$220+tax to replace all four calipers with reman
$200+? to replace the master cylinder

I like the E30's but its killing me (I know all old cars would have similar headaches) lol.

dcramer
11-16-2011, 09:51 AM
well its your brakes ... If you really don't know what you are doing take it to a mechanic

duaux
11-16-2011, 01:07 PM
I think I'll be fine. Thanks.

DIY
11-17-2011, 03:26 AM
I've rebuilt my calipers and in all honesty its the easiest thing in the world. I have the Girling ones. If if sticks only under hard braking it could be the rears that are bad, but thats probably if its just the calipers. If you see scuff marks its bad... a rebuild kit is 15$ I think for 2 fronts, I forget how much the rear was but its dirt cheap usually. Its somethin to try if your up for it, as a bonus you can properly strip the rust from your calipers and paint em good! You will get newseals with the kit, you might need the rubber boots that cover the sliding pins... if their cracked you could have alot of corrosion in the bushings, a wire brush and a good glob of caliper greese will help sove it...

duaux
11-17-2011, 09:07 AM
Hey DIY: Thank you for the assurance.

I did find some DIY (no pun intended) on both r3v and m30tech, I think I may go that route... the actual slider pin bushings are more expensive though. either way I will have to take the calipers off to inspect them first.