timberwolf63

I replaced my power brake booster about two or three months ago, this last week i noticed the dreaded air sound again and upon further investigation I noticed some fluid leaking from the master cylinder at the booster connection, I just replaced the master cylinder in hopes that the booster is still ok. As soon as I started the car and pushed my brake pedal it went straight to the floor and stayed there, not even any loose play to get fluid back in the system just a thump and nothing else. if i manually pull the pedal back up it will simply just thump back to the floor when i push it.
Damn i hate being a back yard mechanic any help would be greatly appriciated.
Do i need to replace my booster again?
Thank you for your help.

Peter

chucks88

It sounds more like a M/C issue than a booster problem to me. Did you buy a re-manufactured M/C. I just put a re-manufactured M/C in my car about two weeks ago from NAPA only to find that I will have to pull it out a swap it for another. It isn't holding pressure

You can test your booster by pulling the vacuum line off of it, and hooking a Mighty-Vac(or similar)to it, draw some vacuum and see if it is holding vacuum.

Kinkajou

Had the same exact problem about a month ago.
I was returning from a twisty road and had to make an emergency stop. After that I had no brakes what so ever, fortunately I was near my house and drove back safely.

I removed the MC and there was no leak.
I changed the brake fluid ( which was probably never changed), purged the system as stated in the Helms manual, and I have brakes again.

I will still replace the MC because I do not really trust it.

I understand that to test your booster unit you have to put your car in neutral, depress the brake pedal with some pressure and then start the car. You should feel the pedal going down slowly.
That is the power assist.
But in order to do that you need to have your MC working.

Maybe the brake fluid boiled and you have an air bubble trapped in the system.
I would start by purging the whole system.

Good luck

CentralCoaster

Did you bench bleed the master cylinder?

AZC4Guy

did the booster rod disconnect inside the booster?

czissman

I don't think your pedal dropping to the floor be caused by your booster. My ride's a 92 and I had a similiar problem that was related to the slave cylinder at the bell housing. After installing your new MC, did you bleed the entire system, including the slave cylinder? In my case, my slave actually failed and I had to replace it, but before I bled it properly I had similar trouble.

CentralCoaster

If your master cylinder is full of air, the brake booster could probably suck the pedal all the way to the floor when you push it. I wouldn't think the booster vacuum could overcome the brake return springs, but I've seen where bottoming out pistons in a bore causes them to bind.

timberwolf63

Thanks for all your help everybody,
I decided to just bite the bullet and torch the car, Just kidding...
I bought a new power booster and master cylinder, bled the entire system and behold I have new brakes it stops quick and straight, it is better now then it has ever been. This makes being a backyard mechanic all the more fun when you correct the problem by yourself and the help of this forum.
Once again thanks for all the advice.

Peter

redwing76

Thats important and its says to do just that right on the box. But some folks read the directions after the fact. I know that I do.