Brakes sticking/holding/dragging

[fineinbase4]

First post! The ink on the e30's title hasn't even dried yet, but I'm ready to dig in. :borg

The brakes will continue to hold after the pedal is released such that the car won't move if I'm idling on a hill. I can also hear them slightly when coasting to a stop.

I will relubricate the caliper pins, but this seems unlikely to be the main problem, as the brakes release as soon as the engine turned off.

The braking system was completely rebuilt by the previous owner and consists of:

e36 m3 front calipers
e36 318ti rear calipers
e32 master cylinder
e21 brake booster
ABS delete
stainless lines
BMW amber fluid, recently flushed

Everything worked properly as recently as several months ago, but since then, the car has sat in the driveway. I've driven it about 500 miles with no improvement.

I'd characterize the pedal feel as 'hard'. The brakes work effectively. It's been cold out, which is likely preventing any heat issues, but certainly this isn't a problem to ignore.

It would seem that if master cylinder or the booster were to fail, this would cause a decrease in the power-assist on the brakes, whereas my problem is that the boost seems to be too much.

I'm new to e30's and don't have much experience with power-braking systems, so any suggestions would be appreciated!

[fineinbase4]

Update:

I re-lubed the caliper pins. They were dry, but the issue persisted.

It seems like the problem relates to pedal position. It doesn't seem to retract completely after releasing the brakes. If I manually pull it back (only about 5mm), the dragging goes away completely.

What is the mechanism for the brake pedal coming back to neutral? What can I do to help make sure it comes back all the way?

Any thoughts?

[Kershaw]

have you tried greasing everything that moves down there? white lithium grease is my go to.

[fineinbase4]

I sprayed everything I can see... didn't seem to have any meaningful impact.

Could it be a problem in the linkage? I see that there's a small return spring, but it seems far too small to have any impact.

[TobyB]

You already diagnosed it- your pedal's sticking. It's holding the booster on a bit.

Crawl under there and see if there's anything physically hitting the pedal,
then take the pedal and linkage apart and see where it's binding.
It'll be pretty obvious.

If it's not, the next place to look is to make sure the pedal's not depressing
the booster a little bit even when it's at full retract.

t

[Seawolf]

Could it be a problem in the linkage? I see that there's a small return spring, but it seems far too small to have any impact.

Could be that your brake pedal linkage needs adjusting, if the setup is wrong then this may block the master cylinder vent port - though this could also be the result of crap blocking the port or a broken master cylinder high pressure return spring.

If the vent port is blocked then high pressure system fluid cannot return to the master cylinder reservoir and your brakes system will remain pressurized.

Read here for more info on how this works:

http://www.freeasestudyguides.com/brake-master-replenishing-port.html

And how to adjust the pedal linkage:

http://spece30.com/forum/39-brakes-and-abs/71726-adjusting-brake-pedal-height

[Kershaw]

I sprayed everything I can see... didn't seem to have any meaningful impact.

Could it be a problem in the linkage? I see that there's a small return spring, but it seems far too small to have any impact.

On really stuck items, try a penetrating oil. It may take a day or two to get in there and unstick stuff.

[unloadedak]

I did put a new pedal set in there when I put the interior back together; I bought it with AKG bushings pre-installed. I wonder if they weren't installed/torqued properly?

[AndrewBird]

If the clevis on the end of the master isn't thread on far enough, it will hold the brakes on and the booster will slowly pressure the system until it won't move anymore. I would start by looking here. There should be just a tiny bit of play in the pedal before moving the MC. If not, you need to screw the clevis farther in.

[unloadedak]

If the clevis on the end of the master isn't thread on far enough, it will hold the brakes on and the booster will slowly pressure the system until it won't move anymore. I would start by looking here. There should be just a tiny bit of play in the pedal before moving the MC. If not, you need to screw the clevis farther in.

It HAS to be the pedals and bushings. The booster is the same one that was used on two swap cars without issues; length was properly matched to a stock E30 booster.

[fineinbase4]

It HAS to be the pedals and bushings. The booster is the same one that was used on two swap cars without issues; length was properly matched to a stock E30 booster.

Probably just the pedal bushings that would need to be replaced, right? What part of the pedals themselves would wear out or go bad?