Good evening all,
a new perplexing problem with my 86 300sdl. First of all I have new rotors, brake pads, sensors, and rubber brake hoses. Fluid level in the master cylinder reservoir is normal and not changing. Brakes work excellent EXCEPT occasionally at idle at a red light my pedal will sink slowly to the floor almost.
At first I thought master cylinder, but no leakage and no fluid level drop.
In my driveway with the car off, I can pump the brake pedal two or three times to release all of the built up vacuum in the booster and the pedal sits there hard as a rock. So I am thinking not the master cylinder.
Today at a red light it did it again so I pumped the brake pedal 4 or 5 times and the pedal comes all the way back to normal, but I hear a whooshing sound at my feet. Could my booster be leaking? Could I have a vacuum leak somewhere? My transmission shifts perfectly so I was ruling out the vacuum source for it, BUT... a Climate control vacuum leak? Could that affect your brakes?

Thanks in Advance for all comments.

__________________
John
1986 300sdl
1985 380se