ZR1 Brake Problem

[Charles Arnold (3745)]

I acquired a 90 ZR1 that sat for 7 years. Put in new brake fluid by bleeding at each wheel. After driving for 15 minutes brakes locked up and brake pedal became very hard. After sitting for 20 minutes problem went away. Thought it was just rear brakes with pistons sticking so I replaced rear calipers. Drove again and same problem with the front brakes and possibly still the rears but both fronts definitely locked up. After cool down everything works fine. Anyone have a diagnosis and solution? Thanks Chuck.

[Clem Zahrobsky (45134)]

the inside of the flexible lines could be causing

the problem as they get pin holes in the inter lining and the pressure of applying the brakes will cause to expand blocking the return of the fluid. a friend had this happen to his corvette and the brakes got so hot there was a fire

[Charles Arnold (3745)]

Re: the inside of the flexible lines could be caus

Sounds scary but Not such a hard fix hope you are right.

[Mike McCagh (14)]

Re: the inside of the flexible lines could be caus

agree with clem. good luck. mike

[Charles Arnold (3745)]

Re: the inside of the flexible lines could be caus

Thanks guys since the pedal gets very hard and goes down some have advused it could be a vacuum problem. Also problem goes away 10 minutes after sitting. Any thoughts on a vacuum issue?

[John Hinckley (29964)]

Re: the inside of the flexible lines could be caus

I'd bet on deteriorated flex hoses becoming check valves.

[Jim Trekell (22375)]

Re: the inside of the flexible lines could be caus

It has happened to me, no fire but lots of smoke coming from the right front, thought it was on fire. Drove it to work that morning and going home it just happened. Thought it was the caliper at first, even replaced the caliper like you. Wasted time and money. Having to replace one hose the rest were just as old and replaced all of the rubber hoses.

[Charles Arnold (3745)]

Re: the inside of the flexible lines could be caus

Only thing that makes me think something different is all four lock at once. If it were lines seems like it would just be one or two. Could the vacuum assist check valve be a problem or a clogged return on the master cylinder?

[Clem Zahrobsky (45134)]

Re: the inside of the flexible lines could be caus

is the MC pushrod adjustable,i could be too long and heat expansion taking over.