CO track thread

[fsmtnbiker]

And now after doing more reading I think I might need a new MC soon. My pedal will sometimes be a normal amount of soft and once I let off the quickly apply brakes again they are nice and firm. They have never sank to the floor though. Thoughts?

This sounds more like bad caliper mount bushings or a bad wheel bearing.

A bad master will slowly sink with pressure applied until it reaches the floor.

The most common cause of a bad pedal with no air in the lines (and no other recent brake work) is a bad wheel bearing.

[Cloudbase]

I have a pedal that slowly sinks about 1-2'' when pressed. I've replaced the master cylinder 3 times with known used ones. I was thinking it was a bad caliper. Why would a bad wheel bearing replicate that symptom?

[Bimmerman325i]

I'd imagine a bad wheel bearing will cause the wheel assembly (rotor, blah blah blah) to wobble enough to where the caliper pistons no longer act parallel to the rotor face. It'd be tiny amounts of misalignment, but could have an effect. Otherwise...I dunno.

[blefevre]

Also interested in the wheel bearing info. One of my fronts is only a year old and there are no noises what so ever from the other one. I have new calipers and lines in the mail right now so it sounds like I should just get those on and see what it does.

[fsmtnbiker]

I have a pedal that slowly sinks about 1-2'' when pressed. I've replaced the master cylinder 3 times with known used ones. I was thinking it was a bad caliper. Why would a bad wheel bearing replicate that symptom?

Also interested in the wheel bearing info. One of my fronts is only a year old and there are no noises what so ever from the other one. I have new calipers and lines in the mail right now so it sounds like I should just get those on and see what it does.

If the pedal gets better if you pump it multiple times, or if you notice that you have a very low pedal only after taking a corner, it is indicative of a wheel bearing problem. The bad bearing allows the rotor to push the pads apart further than they normally would be, effectively 'compressing' the caliper a little bit.

Bad guides allow the caliper to not sit square to the rotor at rest, which means you have a soft pedal until the pads wear to match the geometry of the guides. I see this problem fairly often in E36's, the old pads are worn with very bad taper, and when new pads go in the pedal is softer until the pads are driven for a while and the wear pattern is corrected. Obviously the right fix here is new caliper guides.

If you apply pressure to the brake pedal and it goes down a ways, stops, and then slowly continues to compress, your master cylinder is leaking fluid out of the pressurized area and back into the resevoir... OR, you have a fluid leak somewhere else in the pressurized side of the system.

Bad calipers usually show up as a pull to one side under braking, typically because the piston is binding or seized in the caliper. If your car pulls to one side under braking, your problem is likely on the opposite side of the car. It will always pull towards the side of the car that the brakes are working better on.

[clarkkey594]

If the pedal gets better if you pump it multiple times, or if you notice that you have a very low pedal only after taking a corner, it is indicative of a wheel bearing problem. The bad bearing allows the rotor to push the pads apart further than they normally would be, effectively 'compressing' the caliper a little bit.

Bad guides allow the caliper to not sit square to the rotor at rest, which means you have a soft pedal until the pads wear to match the geometry of the guides. I see this problem fairly often in E36's, the old pads are worn with very bad taper, and when new pads go in the pedal is softer until the pads are driven for a while and the wear pattern is corrected. Obviously the right fix here is new caliper guides.

If you apply pressure to the brake pedal and it goes down a ways, stops, and then slowly continues to compress, your master cylinder is leaking fluid out of the pressurized area and back into the resevoir... OR, you have a fluid leak somewhere else in the pressurized side of the system.

Bad calipers usually show up as a pull to one side under braking, typically because the piston is binding or seized in the caliper. If your car pulls to one side under braking, your problem is likely on the opposite side of the car. It will always pull towards the side of the car that the brakes are working better on.

I don't know about you guys but I like having Chris on the boards. lol

[blefevre]

No kidding! Now here's my most annoying one. Dead zone in the steering.

Problem: When turning left or right, but it is more noticable when turning left, there will be a dead zone of about 45-degrees where no steering will happen. If I turn lightly I can sometimes avoid it and the steering response will be normal. When parked with no PS it will do it all the time when turning the wheel. I'm guessing it's the rack went bad somehow, but maybe I'm wrong!

[Bimmerman325i]

that seems odd. I don't have a solution, but that sounds really odd.

[blefevre]

It can be scary! I have learned to predict it but my wife is worried I might lose all steering sometime. I have done control arms, control arm bushings, tie rods, PS fluid flush, no PS, tightened that nut on the steering column by the pedals, alignment.

[fsmtnbiker]

Definitely something broken inside the rack it sounds like. It might be worth inspecting the steering column closely at all of it's joints, just in case.

[Cloudbase]

Thanks Chris. My symptoms all point to a leak or a bad MC. But I've replaced all my lines, can't find any leaks, and replaced the MC twice after bench bleeding. That left me thinking a bad caliper. It def doesn't pull in any direction though. Hmmm....

[blefevre]

You can try my old calipers once I get my new ones if you want.

[blefevre]

Definitely something broken inside the rack it sounds like. It might be worth inspecting the steering column closely at all of it's joints, just in case.

Bah, not what I wanted to hear. Autosport werks pretty much said they won't swap a E36 rack in and a new E30 one is such a waste. I need more free time....

[Bimmerman325i]

It's not a bad swap on an e30 to put an e36 rack in, probably a weekend. I'd go with the 95 M3 rack since it's got better geometry than the Z3 rack (scrub radius). The Z3 is much quicker lock to lock though, twitchy/darty almost. I haven't driven the 96+ M3 rack though.

[blefevre]

I would be fine with any E36 rack, whatever is cheapest rebuilt.