Brake pedal squeaks!

[jolllibean]

Hi all!

When the ignition is on and you're stepping on the brake pedal, has anyone ever got a squeaking sound from the pedal? It souds like a mouse squeaking, or a bit like farting. I traced the sound to the servo, I believe. I've also greased the area under the steering where the brake pedal meets the dash, but that doesn't help. Today I bleeded the brakes and the sound disappeared for about half a day, but returned at night. Anyone got any idea where the problem is? Thanks in advance!

[Kalevera]

Bean,

First, read this:

http://www.bimmer.info/forum/showthread.php?t=14093

Without knowing what kind of car you have/for what market it was produced, we can't give as accurate of an answer.

Here's what I think. If the car has a vacuum brake booster (ie - brake BOMB), you've got a bad valve in it. These units work on the principle of changing the atmospheric pressure on one side of a rubber diaphram, essentially subjecting it to engine vacuum. The other side of the diaphram (that mounts to the firewall and passes through into the driver's footwell area) has a valve designed to quietly exchange air between its chamber and the car's cabin. They can often get clogged with dust and wheeze.

best, whit

[Traian]

Mine gets a bit of a squeak too, usually right about when the windshield stops squeaking. Tag team you see. Anywho, I've got nothing to contribute, just turn up the stereo...

[jolllibean]

Hi Lowell,

Thanks for your thoughts. My apologies for missing out the car details. Mine is a 95 520I Auto. Hope this is enough info. Good news is that I did try a search but didn't turn up wif anything.

Your explanation sounds logical. Looks like there's no easy fix for me then...

Bean,

First, read this:

http://www.bimmer.info/forum/showthread.php?t=14093

Without knowing what kind of car you have/for what market it was produced, we can't give as accurate of an answer.

Here's what I think. If the car has a vacuum brake booster (ie - brake BOMB), you've got a bad valve in it. These units work on the principle of changing the atmospheric pressure on one side of a rubber diaphram, essentially subjecting it to engine vacuum. The other side of the diaphram (that mounts to the firewall and passes through into the driver's footwell area) has a valve designed to quietly exchange air between its chamber and the car's cabin. They can often get clogged with dust and wheeze.

best, whit

[Kalevera]

You might want to remove the lower trim and vacuum the area to see if that helps. Otherwise, replacing the brake booster isn't that big of a deal. Four nuts on the inside of the firewall, two on the brake booster/master cylinder junction, and a vacuum hose from the intake manifold. And I'm sure there are tons of used ones floating around in junkyards, assuming you're in Europe.

best, whit

[jolllibean]

Thanks Lowell or whit! Will try that and let everyone know the result.

[jolllibean]

Whit, guys,

So I took Whit's advice and bought a reconditioned brake booster from the scrapyard and got it installed. Whoa, the brakes feel like a new car's and there's absolutely no more wheezing sound coming from the bomb. Once again, I am amazed at the precision of the advice provided by this board. Ok, but I must say that it took me a long time to take out the brake bomb together with the master cylinder, as there were many items in the way. I would suggest that anyone attempting this set aside the afternoon to do it.

One glitch though, and this is where I need help again. After I had finished fitting back the interior trim pieces at the glove box area, I discovered that the backlighting for the speedometer, the climate control, the fog light / front light switches were not working anymore. The other interior lights like the dome lights were all working. So I thought that I must have blown a fuse, in particular one that joined to the speedometer and the climate control console, cos these were the only ones whose backlights were not working. Got it checked out with the mechs, but they said all the fuses were working. I'm now wondering if I could have accidentally clipped a wire somewhere in the glove compartment area, or near the brake bomb, but my visual inspection just didn't reveal anything. Does anyone have any ideas? I'm really quite clueless. Btw, the cars a 95 520IA RHD.

You might want to remove the lower trim and vacuum the area to see if that helps. Otherwise, replacing the brake booster isn't that big of a deal. Four nuts on the inside of the firewall, two on the brake booster/master cylinder junction, and a vacuum hose from the intake manifold. And I'm sure there are tons of used ones floating around in junkyards, assuming you're in Europe.

best, whit

[632 Regal]

you want to check the fuses with a multimeter, although they may look good somethines ther burn and you cant tell visually.

Whit, guys,

So I took Whit's advice and bought a reconditioned brake booster from the scrapyard and got it installed. Whoa, the brakes feel like a new car's and there's absolutely no more wheezing sound coming from the bomb. Once again, I am amazed at the precision of the advice provided by this board. Ok, but I must say that it took me a long time to take out the brake bomb together with the master cylinder, as there were many items in the way. I would suggest that anyone attempting this set aside the afternoon to do it.

One glitch though, and this is where I need help again. After I had finished fitting back the interior trim pieces at the glove box area, I discovered that the backlighting for the speedometer, the climate control, the fog light / front light switches were not working anymore. The other interior lights like the dome lights were all working. So I thought that I must have blown a fuse, in particular one that joined to the speedometer and the climate control console, cos these were the only ones whose backlights were not working. Got it checked out with the mechs, but they said all the fuses were working. I'm now wondering if I could have accidentally clipped a wire somewhere in the glove compartment area, or near the brake bomb, but my visual inspection just didn't reveal anything. Does anyone have any ideas? I'm really quite clueless. Btw, the cars a 95 520IA RHD.

[jolllibean]

Hi Regal,

Actually, I got the mechanic to check out the fuses, he said they were all working fine. But is there a particular fuse that affects only the speedometer backlights, the climate control, the headlights, foglights backlights?

you want to check the fuses with a multimeter, although they may look good somethines ther burn and you cant tell visually.