I have a 1962 Impala with a 409 engine and drum brakes and new stainless lines throughout. The engine runs hot. If I drive the car more than a few miles (maybe 25), the brake pedal is at the top and I cannot push it down at all until the engine cools down. During this the brakes are somewhat locked up. Someone told me the brake fluid is boiling. Is this possible or is something else going on.