Master Cylinder or Brake Booster?

You need a new booster...

http://www.justparts.com/Auto_Parts/20156132?q=1999+PONTIAC+GRAND+PRIX+POWER+BRAKE+BOOSTER

I have a great idea. Drive it carefully to a mechanic. Have him fix it.

As much as this might hurt egos and checkbooks, it will save you from much mental strain and a possible accident.

I took it down the road. I had brakes, however some air in the system as we didn't bleed the wheels.

I didn't need to finish reading after this point. Pay a pro.

my dad is a home wrencher, has been all his life!

and can only do so much when I got college and work. Would bleed the wheels after the main problem is fixed.

thanks for the help guys.

I'd suggest that your booster is full of brake fluid from your first defective MC..the vacuum inside the booster probably sucked oil out of your MC and filled itself up.

Do as suggested rather than take any further risk ..replace it.

"my dad is a home wrencher"

They are a dying breed, take it to a qualified mechanic before you have a nasty accident.

Only qualified people should work on brakes, there are so many errors that may take months to come out....

By the way, even brand new cars can have failures in this area.....personal experience!

You probably have a leak in the diaphragm of the booster and the vacuum is pulling brake fluid out of the master cylinder and into the booster housing. When enough fluid builds up in the booster it is being forced out of the booster housing and onto the engine when you apply the brakes. Replace the booster unit.

grav you probably nailed it on the head. Been doing a ton of research and this is what we have found with chronic master cylinder failures.

Debating on whether or not to exchange for another reman or try to get a refund and buy a professional grade MC. Also looking around for a booster.

new car in future as well.

If you're determined to work on it yourself, put both a booster and M/C on it at the same time.

Better, as several as suggested, get a pro to take care of it.

No comment upon ability-the liability of someone who may not be professionally trained to do this is tremendous. Several cases have come through the courts with DIYers coming out on the negative end of lawsuits working on safety related systems on cars.

I reckon its the master cylinder.

If it was the booster then the booster would just not work. have you checked that it is functioning?

The only way for brakefluid to enter the booster can is through the rear seal of the MC. Extreme vacuum might pull it through but any perforation in the diaphragm would render this impossible, so not likely a buggered booster. I can't think how above normal vacuum might be occuring....badly choked airfilter, clutching at straws there as you would have noticed a huge engine performance drop long before the engine was sucking itself inside out (mini rant here....).

When you removed the MCs was the brake fluid escape route evident?

Rebuilt MCs are troublesome things. Get a new OEM or aftermarket MC.

Hello Wal. Seems that previous posts while they have the correct idea,they are using the wrong terms to identify parts in the brake booster. Replace the term perforated diaphragm with perforated front vacum seal in the booster and the 15-18 inches of vacum will pull brake fluid past the rear master cylinder seal.

I'm glad this thread I made is finally getting the attention it deserves, its a screwy problem sprinkled with some mystery.

What I do know is the booster has approx 240 lbs pushing/pulling force. I would say its possible to pull fluid and brake the seal or ruin the primary piston.

As for the safety concern I can understand. However my dad's buddy used to be a mechanic, and he wouldn't let us roll off the driveway without things fixed properly. Although liability I can understand as well.

I'm a college student guys, what do you expect? I can't just go out there and buy a new car or spend $1,000 at some place to fix this issue - when the car is only worth $1,200.

I wouldn't drive it if I didn't think it was safe by any means. I'm not some d***** like that.

I only made the comment that I did, because you worked on it and then put it on the road without bleeding the brakes......................that's a no, no.

Anyway, moving on..................I can only add, (from experience), that you can no longer assume that remanufactured parts are good...................ever. I swear, some of this stuff, they just clean it off, spray paint it and resell it. Complete garbage.

I didn't read every post, but I think one of them recommended replacing the booster and M/C together. That's what I would do. You may even be able to find them in a low mileage car at a junk yard.

The comment:-

I only made the comment that I did, because you worked on it and then put it on the road without bleeding the brakes......................that's a no, no.

Was also my personal tip for a dangerous bit of amateur "wrenching"......nothing worse or simpler that forgetting to bleed the brakes and NOT checking them before driving even 1"....

I once changed out the master cylinder on my truck...........everything by the book. Bench bleeding, etc. Everything went perfectly.

I did the work in my side yard, next to the house. To celebrate a job well done, I drank myself a few beers and relaxed for a little while.

Long story short, I went to drive the truck back up to the driveway and backed it straight into a big ditch. Had to call a tow truck to pull me out. $75.

I forgot to bleed the brakes.

As a very young man (17) I did the same, luckily I kept the handbrake in top condition.....

You only forget once! (both possible results of this comment are intended!!)

I had an '83 Accord which had the same problem. The seal between the master cylinder and the brake booster went bad. The booster then filled up with brake fluid (over a period of time), and I kept refilling the Master cylinder. After a couple of months, I finally got around to replacing the master cylinder and everything was OK for a while, but eventually the power part of the brakes quit working. When I pulled the booster, it was full of brake fluid. The fluid had deteriorated parts in the booster, and it no longer worked... so normally, the brake booster shouldn't go bad, but it is not meant to contain brake fluid.

That Honda was the BEST car I ever had, but after 250K miles and 20+ years, it reached the point where it was not worth the money and time to keep it going so it went away.

Bill

If the fluid came out of the master it is bad.

Once it was allowed to stay inside the booster, it also became bad.

Replace them as a pair, if there is a reason to suspect the booster. Be safe.

replaced brake booster, got a new MC.

it was absolute hell to get the original brake booster out. With new one in, all buttoned up.

rough idle, vacuum leak brake booster. THE BRAKE BOOSTER IS BAD.

!&*!(*26!(*@^&*!@%&*!%^)!!!!!!!!!!!!!!!!@*!*)@)!@

at this point im thinking of just getting a new car.

Anyway, moving on..................I can only add, (from experience), that you can no longer assume that remanufactured parts are good...................ever. I swear, some of this stuff, they just clean it off, spray paint it and resell it. Complete garbage.

From post # 14. I went through this with an AC compressor a couple of years ago. I felt like blowing up the car and the parts place that kept selling me junk.

Before you go tearing everything apart, double check every hose, and particularly any hard plastic connectors or elbows that lead to the booster. Check them good..............they can be cracked and look fine.

Was the booster a reman.?

I feel your pain..................been through it more times than I want to remember.

Just as an add on to yours K...

My Honda had a "One Way Valve" in the vacuum line running from the engine to the brake booster. I am NOT familiar with the OPs vehicle so he may or may not have such a critter. It might be something for him to check on.

Bill

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UPDATE:

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Booster came in from Rock auto. Re-Manufactured, but that's ALL they sell. I can't find any brand new. Regardless this booster is in top notch shape.

Put in the booster, new MC, buttoned up everything, BLED THE BREAKS.

I have from what I can tell only in my driveway, pretty sweet brakes...

now here is the bad part.......................................

*!*_!_*&@_(@!&@(!*!!!!!!!!!!!!!!!!!!!!

VACUUM LEAK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

rough idle, vacuum leak, you can hear the hiss from inside the car, brakes feel absolutely fine. Car elopes at idle, its not pretty... detached the rubber vacuum hose from the booster, put finger over it and idle is perfect.

Not sure what to do anymore...

At least it's an audible hiss.

Get a length of hose, hold it to your ear, track down the hiss, and fix the leak.

Your brakes may feel perfect in the driveway, but if there is a vacuum leak from the booster, you won't have power brakes.

are you saying I should maybe take out the booster again, find the leak, and like epoxy it?

maybe even do it under the dash, without taking the thing out.

yea not going to happen. I just did everything I could from inside under the dash. Vacuum leak hiss is just getting worse.

3-4 master cylinders and 2 boosters now.

I'm ready to take a sledgehammer to my car.

How do you know that the booster was in top notch shape? Like I said I got 4-5 reman AC compressors a couple of years ago and none of them were good. Same story from the parts place.................there are only one or two places in the country that remanufacture parts. This is looking like an opportunity to me. Remanufacturing parts is not difficult work.

I might just look into it.

maybe its just my wishful thinking.

Ive been through 3 MC and 2 boosters now. I've also never had a problem with rock auto.

REMAN is an absolute nightmare.

Im sending this one back, picking one up from advance auto. That one will also be reman.

is that DOESNT WORK. Im getting a new car ASAP

this has turned out to be a complete and total nightmare and finding rides to college back and fourth is rrreeeaalllyy wearing me down.

From the conditions you describe, it sounds like the wiper-breather is not sealing the brake pedal push rod correctly. Have a look where the brake pedal push rod exits the booster. If you can see the rubber cover and felt material has slid away from the booster, and on to the push rod, you can simply return them to their designed location. It should be a very obvious thing. If it does not look obvoius to you ask an experienced brake repair person to look. Otherwise, it is exchange time again.

Caution Spell-check sleeping still.

I know the nightmare. I've always had a good experience with Rock Auto myself. Unfortunately, the same remanufacturers supply all of them.

Yeah, buy one locally. I would highly recommend having someone find a way to pull a vacuum on it before you put it in the car. You may be able to make a plate to fit over the hole where the mc goes, and hook it up to your actual vacuum hose in your car. If it's hissing/leaking, you will know about it before it's installed.

On second thought, you may not need to block the mc hole at all to find out if the diaphragm is functioning properly. I'm guessing not.

ehow sucks, but double check the one way valve, as another poster mentioned. This is an adequate description.

http://www.ehow.com/how-does_4829365_testing-procedure-brake-boosters.html

Let me know how it goes.