chll69

I have a 1986 C4 and my problem is that when i hit the brake sometimes it squeals (high pitch sound) obnoxiously loud, i found that when sitting still and i push the brake pedal to the floor all the way that i can get the sound every time, like i said other times while driving it will go off even if the brake is not fully engaged and even happened once when i just started the car up? any ideas, i had the brake booster and master cylinder replaced about a year ago.

powerpigz-51

If it happens when the car isn't moving, that eliminates all the things that rotate. Narrows it down to the brake pedal assembly or a caliper (which I don't think move much).

chll69

I was thinking maybe an air hose or brake line, but im not leaking any fluid?

powerpigz-51

Check the hose to the brake booster.....is it a balloon-like squeal? or metal to metal? Does the engine have to be running to make the noise?

chll69

I would say maybe more a balloon like, it is a very high pitch sound, cant hold the brake too long because it starts to really bother my ears, i will try pulling that line to see if anything changes, thanks

powerpigz-51

ahhh....its a continuous squeal? engine running only? almost has to be the serp belt. 2nd guess....brake boost diaphram

chll69

Only when the car is running, how would it be the serpentine belt? The brake booster was what i was thinking possibly.

powerpigz-51

You said you replaced the booster a year ago....was it making the noise then? (before replacement). You also said that it made the noise without the brakes being applied and when you started the car. This is more "belt" like. Maybe depressing the pedal and illuminating the brake lights is loading the alternator enough to squeal the belt. Also....the tensioner could be squealing. Anyways....just guessing on my part. Get someone to get it to make the noise and poke around with a stethoscope, pipe or screwdriver until you narrow it down. Good luck!

chll69

So i was just working on it and I figured out what is is but dont know why it doess it because it never did before. The Brake Booster hose that goes from the back of the Air box to the brake booster seems to be the culprit, when i detach the hose from the brake booster and mash the brake i get no noise! When i reattach it to the brake booster and mash the brake i get the noise again?> Is it okay to keep the hose detached? Any idea why it does that? Is the brake booster going bad maybe?

chll69

Right replaced it JAN 2010 so a year an a half almost. Never ever heard the noise before this.

powerpigz-51

The hose is a vac source.....when you unplug it, the diaphram no longer has the vac pressure to make it squeal. Sounds like the diaphram has a hole in it. Without it, you will not have power assist to the brakes and a very stiff pedal and longer stopping distances. As well as a giant vac leak on the motor, you will have to plug the hose.

chll69

So is it still drivable if i plug the hose? I just need to take longer time to brake with it like that, right? So i need to replace the brake booster again it sounds like, right?

powerpigz-51

Yes. but drive at your own risk. You might try sucking on that hose and see if it holds pressure. If not, its toast. (if the hose and connections are good) Also...with everything hooked up, place your foot on the brake pedal, then start the car. If you feel the pedal depress slightly, the booster should be ok.

chll69

ok will do, thanks for all your help!