MY CAR WILL NOT STOP, THE PEDAL JUST GOES TO THE FLOOR AND MAKES A AIR NOISE. I JUST PUT A NEW MASTER CYLINDER ON,NEW PADS AND BLEEDED THE SYSTEM. STILL THEY WILL NOT STOP. CAN THE PROBLEM BE THE BOOSTER? WONT IT STOP A LITTLE EVEN IF THE BOOSTERS BAD? PLEASE RESPOND WITH ANY INFO. I NEED TO GET MY CAR RUNNING AS SOON AS POSSIBLE, THANKS

 

Yes, if the system can hold pressure it should give feedback to the pedal. My guess is that you resivoir is empty now. Rear wheel cylinders can blow out, but that should still give some feeling in front brakes. Your problem is absolutely impossible if the system is holding pressure.

 

did you bench bleed the master cylinder before putting it on? if not you need to.

are there leaks anywhere? are you sure you bled correctly? i think a bad vacuum booster will result in a very hard pedal.

go easy on CAPS LOCK too

 

I propery blead both the master cylinder and the brakes, the resevoir is full with all new fluid and there are no leaks anywhere. The vacume going to the booster has alot of suction as well. Hoa many times do you guys blead you brakes at a time? I blead mine twice a piece. Also, i have front disk and rear drum, if i was to blead the fronts, master cylinder but not the backs would this cause such a problem. I mean the car cant even hold still when stoped in drive. It stops barely if at slow role in nutural. Thanks

 

Like I said, something aint addin up. Start at the pedal and go forward, something's horsed up somewhere. Make sure the pedal is physically connected to the MS. BTW if you can bleed the sys. then pressure should be getting to the piston. If you're not leaking fluid, are able to bleed, and the res stays full then I'd say it's time to tear it all down and start over.

 

i was affraid it would come down to this. What do you mean by the pedal should connect to the master cylinder, how do i check? if the booster went ot would that happen?

 

A bad booster will produce the "air" sound you're hearing but the pedal should get firmer , not travel to the floor.

It is possible you got a bogus master cylinder. I've had that happen before - from the dealer no less. If the master cylinder is bad, the pedal will travel to floor and the brakes won't hold.

Like the others have suggested, you need to go step by step and examine everything to make an accurate diagnosis.

 

Did you check the depth of the hole in the new master cylinder
against the depth of the old one? I REMOVE all bleeders and let
gravity do the dirty work. After they are bled, I put the bleeders
back in and tighten them. Then I have an assistant push on
the pedal and I loosen both lines at the master cylinder at the
same time. When the pedal is to the floor I tighten the lines and repeat the sequence until the bubbles of air stop comimg out
and the pedal is hard.

 

Doesnt the bleeding kit that came with it do the same thing? Or do i have to do more than that?

 

Yes, it is supposed to do the same thing. A mechanic at a
Pontiac dealership showed me the above method of bleeding
brakes years ago and it has always been quick and effective.

 

I would have to say it's vacume related. Check the check valve. See if there is vacume at the booster ant after the check valve. Very well could be the booster. That's what happen to me when my check valve broke.

 

check the proportioning valve to i have sen these cause this problem. In fact my buddy recked his car when the brakes failed. It was the prop valve. he said he went to stop and the pedal just went to the floor. ran a red light and got t-boned. also do you have ABS this could also be the prob. I'm not sure but I think there is a specific way to bleed a system with ABS.

 

This is exactly what happened to my car a few months ago!

Here were my symptoms and what was done to fix the problem, this way you can compare the symptoms of your car to what I had, perhaps this can save you some time, trouble, and money.

Symptoms:

* Car fails to maintain a full stop, even when the brake pedal is pressed all the way down.
* Repeatedly tapping the brake pedal (better known as "feathering" the brakes) does not build up enough pressure for the car to come to a full stop.
* From a roll, the car can decelerate (slow down) quickly if the brake pedal is pressed, but the car cannot fully stop.

What was done; keep in mind this helped, but didn't ultimately solve the problem:

* Power brake booster replaced
* Master cylinder replaced
* Verified that pads, shoes, and shoes were in proper working condition
* Verified that the brake fluid resivoir was filled with non-contaminated, up-to-specification brake fluid
* Verified that the condition of the tires were good (eliminating any possibility of traction loss contributed to the problem)

What was determined was wrong:

The proportioning valve (a valve that distributes the brake pressure to both the front and rear wheels) was damaged and needed to be replaced.

Since our F-Bodies have the FR setup (Front engine, Rear drive, also known as RWD), the wheels that make our cars move are in the rear, and a damaged proportioning valve can cause brake pressure to not get to the rear wheels, which explains why your car is not able to maintain a full stop. You may have also noticed that, if the car is in Neutral, it's a lot easier for the car to stay at a full stop, since the rear wheels are not moving at all (assming you're not on any kind of hill, and on flat ground). If you have 4-wheel disc brakes installed, you might have noticed that your car can slow down quickly while at a roll, even though it can't stay still when at a stop. This is because there is plenty of brake pressure going to the front wheels, which aid in slowing down the car, but ultimately, don't keep the car fully still.

You mentioned a hissing sound coming from the rear when you tap the brakes. A bad proportioning valve can be to blame for this as well, since you're essentially losing brake pressure when the rear brakes try to make contact with the rear wheels to slow the car down; usually, a crack in the proportioning valve will produce a sound like this.

While you're at it, you might want to inspect the hoses that are part of the brake system to ensure that there aren't any additional cracks or related damage that could cause brake pressure to be lost.

If you're comfortable doing this yourself, by all means, go for it!

If not, or if your schedule is to the point where you can't afford to take the time out of your day to do the repairs yourself, take the car to a shop that will do it, AND WILL WARRANTY THEIR WORK! Your safety (and the safetye of others that are in the car with you) will be affected as a result of their work, and the car's occupants' lives are well worth the extra money you pay for in order to get the warranty.

In any event, especially if you live in a hill-based area, get this done ASAP!

Hope this info helps, and stay safe out there!

 

Here I go again with my "advertisement" (I -should- get paid!!)... visit http://www.brakebleeder.com and get the V12 w/Smart Pak. That thing fixed my brakes! Bench bleeding our m/c's is a btch because of the quick take-up valve- it sucks air in like you wouldn't believe. The video that comes with the V12 features plexiglass master cylinders- you can actually see where the air gets trapped! I bench bled my m/c about 4 or 5 times.

I also took the m/c back and got another rebuilt one. The second was a definate improvement over the first, but I still didn't get a firm pedal. I think that the rebuild companies will rebuild these things, then send them out to sit in a hot, dry warehouse for years. So when we get them, and push the piston in, we tear the seals. You could also spend $25 for a master cylinder rebuild kit. Yeah it seems silly, because you paid 20 for a master cylinder, but at least you'll know two things- 1, you did it right, and 2, the seals will be "fresh". Pop the piston out of your current m/c first and inspect the bore. The early 82-84 master cylinders had a steel (iron?) body and could be honed if they are corroded. The later m/c's have aluminum bodies, and have special coatings inside that a hone tool will destroy. Plus, with honing, you risk getting metal into the quick take up valve.

Oh, one more thing, if you don't want to rebuild the m/c, check the bore anyway. If the bore has a cut in it, it could be letting air in when the rear seal of the primary piston glides over it- and that cut in the bore could slice the rear seal eventually.

Another thing! The dude at Phoenix systems gave me another tip for bad brakes. he told me to get some of those hose crimpers... you see them in stores like Pep Boys, they crimp fuel hoses shut, look like a pair of plastic scissors. He told me to put them on all the brake hoses, and then try the pedal. If the pedal is hard, then there's a problem with one of the calipers. If the pedal is soft, the problem is higher in the system.

You could also find the correct metric (metric!!) plugs for the master cylinder. Put the plugs in, and try the pedal. If the pedal sinks, the m/c has air in it. Pedal hard? Put plugs into the prop valve and try the brakes again. I couldn't find metric plugs so I bought pre-flared brake line from Pep Boys, and looped the lines from the prop valve back into the m/c reservoirs.

Also, note how I said METRIC plugs- none of the bench bleed kits I got with the master cylinders had metric plugs. They were all SAE threads, and air would escape past the plugs into the m/c- exactly the thing I (and you) wanted to avoid.

I have a ton of other tips I've posted before, if you <a href="search.php?s="><img src="images/top_search.gif" alt="Search" border="0"></a> for "brake bleed" by "TomP" in the "Suspension/Chassis/Brakes" forum, you'll find a ton of tips. I went through hell.