brake behavior

[n/a]

I have a 1964 230sl.  the booster and master cylinder have been replaced.  the brakes work fine except that after the car warms up the brakes don't release unless I hit the pedal again a few times.  Also the idle goes up slightly when the brakes are applied with the pedal pushed down at rest.  could this be a vacuum hose problem and if so what can be done to check it.?  what is the simplest way to handle the non release problem?

[Cees Klumper]

Here's older info I collected off Yahoo! that we will get loaded into the technical articles on this site in a few months:

"I recently noticed that pushing the brake pedal at idle causes my engine speed to increase by 100-200 RPM. Suspecting a vacuum leak in the brake booster, I removed the brake vacuum hose from the intake manifold and plugged the intake hole with a rubber ball. The brakes no longer affect the idle speed.  Does this mean I need a new brake booster? Is there another test I should do to confirm the booster is in fact faulty? Are booster rebuild kits available?

Tom Hanson says: MB doesn't supply kits for these boosters. Maybe there is some aftermarket alternative. I have access to them direct from A.T.E at a decent price. Check the booster hose carefully.

When I come to a stop, and apply the brakes, the rpms increase up to 1500-1600. When I release the brake the rpm drops nicely to the 800-900 range again. Note that this is a 4 speed stick shift, not an automatic. I even tried to lift the accelerator pedal to see if somehow the brake is pressing on the accelerator somehow, but it didn't drop the rpms. Hmmmm... any takers?

Sounds like you have a vacuum leak in your brake booster. To test, remove the booster hose where it connects to the intake manifold, and plug the resulting hole in the manifold. The idle should now remain constant when the brakes are applied. Reattach the hose before driving the car to restore the power brakes."