Brakes lock??

[mquinn66]

My brakes have started locking when the car get warmed up and engine bay is hot. I replaced the master cylinder and added a heat shield thinking that was the problem. But after a short test drive today to the store they still are locking after engine bay gets hot and I park the brakes will lock until it cools. I jacked the front wheels and both sides are locked then you can hear it release after cooling about 10 minutes. I had the master cylinder cap off and when it released fluid pushed up into the master. Could this be a bad booster? The entire system is all new including the lines. The booster is a China bendix knock off. It almost seems like the booster is getting hot and not releasing pressure when I let off the brake . Calipers are not stuck. Any help or similar experiences are appreciated.

 

[dvw]

Loosen the nuts holding the master cylinder to the booster. Do the brakes release? If yes. It's possible the booster pushrod is bottomed out in the master.
Doug

 

[Under Pressure]

When this happened to me 2 years ago on my 70 GTX, I took off the master cylinder and looked inside the booster and it was a collapsed mess inside, sent out to be rebuilt and all good now

 

[mquinn66]

Loosen the nuts holding the master cylinder to the booster. Do the brakes release? If yes. It's possible the booster pushrod is bottomed out in the master.
Doug

I will try that tomorrow. But I just swapped master cylinders and the problem happens with both. I measured and set push rod length with a pin tool.

 

[mquinn66]

When this happened to me 2 years ago on my 70 GTX, I took off the master cylinder and looked inside the booster and it was a collapsed mess inside, sent out to be rebuilt and all good now

I wonder if they can rebuild the China knock offs? It is only a year old I guess it couldve failed already.

 

[Under Pressure]

Not sure on that, mine that I sent off was the original

 

[mquinn66]

I will try that tomorrow. But I just swapped master cylinders and the problem happens with both. I measured and set push rod length with a pin tool.

UPDATE.
First thank you to everyone that offered advice.
Second I feel like a dumb @#% for forgetting to mention I have a line lock on the car. The line lock was the problem it was holding pressure on the brakes even though the switch was not activated and only when the car got hot. So I have it bypassed and all is good now. Next decision is do I look for a better line lock? I have a b&m and have always thought of them as a good company for quality but everything is China made now so I'm leaning towards just ditching it for good since I don't race and it was only for me to burnouts easily.