Finally got around to driving my newest creation and found after a few miles that the both front calipers lock up and the peddle gets hard as a rock. I have Wilwood calipers, pads and rotors. The master cylinder and booster are from Summit Racing, the fit was great and another friend of mine is using the same set up with success. After the car sat for 20 minutes everything freed up and worked as advertised, any thoughts please.
If it was just one side I'd guess the flexible line was collapsing inside. Do you have a combination valve or proportioning valve? Also you need a little free play at the pedal, should be able to wiggle the master cylinder pushrod.
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No proportioning valve, and about 1/8 inch of free play. Could air in the line get hot, expanding and cause this condition?
As I see the situation (it happened to me), the only way brakes can lock up is if fluid gets trapped in the system and cannot return to the reservoir. As it heats and expand, it cannot return to the reservoir and pressure builds. Trapped air would not cause the problem in a properly operating system.
Jim is correct about the free play, but it is also possible the front piston sticks and does not return all the way, trapping fluid. Boosters can also be the culpret, but I know nothing about them.
Bill
I had that problem on a bike once. The master cylinder was assembled with the wrong cup seal, which extended over the pressure port even when fully retracted. In that case I drilled a new port in the cylinder but the correct seal should have also fixed it.
Jim
Is it possible Wilwood stipulates what psi residule check valve to use, if any ?
The next time this happens, back off the nuts that hold the master onto the booster. If the brakes release then you need to adjust the clearance between the booster pushrod and the master cyl.as it's not letting the master return fully.
Cheers
Fred
Fred has the answer! Ding, ding. My money is on that. That happened to me on a '69 Roadrunner I put a booster on.
Tim