Strange brake problem!!

airwolf

New Member
Joined
Mar 6, 2003
Here's the deal. Just got motor rebuilt and a new tranny installed. The car sat for about three months. While the motor was out I installed a vacuum conversion kit. Now the car is running but when I drive it the brakes get stuck. It's fine for the first few minutes and then the car starts to slow down and eventually comes to a complete stop without me touching the brake pedal. Then they won't release! I know it's in the rear brakes because they smoke! The parking brake is fully released so that's not it. I tried a little trick that worked temporarily. While the car was running I loosened the rear line on the master cylinder until fluid came out and the brake suddenly released! The fluid actually squirted out like someone was applying the brake. What can cause this??? Air in the line, bad MC, bad booster?? Anybody seen anything like this?? Thanks in advance for any help!
 
I suspect you may have a bad master cylinder. Probably some type of restriction in the master cylinder. Is your brake light on? you also may have a stuck combo valve.
 
I had the same problem after playing around with the rear axle. Turns out the rear brake hose was bad. Apparently letting the rear hang loose with the frame on jack stands was the cause. Might be worth checking out on your car.

Eric Fisher
 
But if he releases the line at the master cylinder and the pressure releases, the lines leading up to the wheel cylinders should be fine. just an opinion
 
Yeah,Thats what I would have thought. I did the same thing, when ever I apllied the brakes the rears would lock. If I cracked open a bleeder valve or any of the lines the pressure would release unlocking it until the next time the brake was apllied. Took me an entire afternoon to figure it out. Eric
 
brake problem

Thanks for the suggestions. I've never seen anything like this before. The brake light does not come on. The pedal feels fine, not too low. None of the brakes were touched during the rebuild other than the conversion kit which I did buy used as a kit. Any tests that I can do other than just replacing the master cylinder?? The brakes feel perfect except for this problem. I'll try bleeding all four wheels and see if that helps. Man, I had no brakes with the powermaster and now too much brakes with the conversion, I just can't win!!!!:mad: Thanks for the help, any other ideas are more than welcome!!
 
Brakes

Turbofish38,
The only difference with yours is they don't lock up every time. It takes a few times using the brakes. Kinda like it builds the excess pressure gradually til they finally lock up. I drove around for about 4-5 miles the last time. It's happened twice so far.
 
Had the identical problem with a Jaguar .Took about a week for rear brakes to tighten and lock up.Bled the rear nipple and they were good to go for another week.Was a bad master cylinder
 
brake problem

Thanks guys, I think I'll try a new master cylinder. Since I did buy this conversion kit used I don't know how old the parts really are. I'll just replace the master cylinder and the check valve and I'll post the results. Thanks for the help!
Don G.
 
Originally posted by air
Here's the deal. Just got motor rebuilt and a new tranny installed. The car sat for about three months. While the motor was out I installed a vacuum conversion kit. Now the car is running but when I drive it the brakes get stuck. It's fine for the first few minutes and then the car starts to slow down and eventually comes to a complete stop without me touching the brake pedal. Then they won't release! I know it's in the rear brakes because they smoke! The parking brake is fully released so that's not it. I tried a little trick that worked temporarily. While the car was running I loosened the rear line on the master cylinder until fluid came out and the brake suddenly released! The fluid actually squirted out like someone was applying the brake. What can cause this??? Air in the line, bad MC, bad booster?? Anybody seen anything like this?? Thanks in advance for any help!

Usually what causes this is there isn't enough free play or its partially applied between the master cylinder and the apply rod on the booster .

basically fluid is trapped in the line as it gets hot it expands applying the brakes.
 
brakes

petesgn,
So would a new master cylinder solve this problem?? Not looking for guarantees, just educated opinions! Thanks.
 
I might cure it. Maybe you got one that was made on monday or friday.

When you undo the two nuts holding the old master it should not spring out should be flush with booster just by holding it .

When you replace it just check to see that you have some play between the rod that sticks out of the booster and the master cyl..:D
 
brake problem

OK I'll check that. Just picked up a new M/C and check valve just in case. And you're right about that Monday or Friday thing, seems like everything I do on those days gets jacked up!!:D It's ging to have to wait a couple of hours cause it's 108 degrees outside right now!:eek: Thanks for the help, I'll post results later tonight.
 
Re: brake problem

Originally posted by airwolf
It's ging to have to wait a couple of hours cause it's 108 degrees outside right now!.



Wow thats hot

about 89 degrees here:cool:
 
brake problem

Thanks to everybody that responded. I just put on the new master cylinder and check valve and guess what? The problem went away!! I drove the car for about 45 minutes and had no brake lockup! The brakes feel really good, a lot better than the powermaster system. Now moving on to other issues! Thanks again everybody!!!
Don G.
 
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