Sounds like your modulator valve is either bad or not getting vacuum.

And I am sure that you are keeping the fluid at the right level. If it gets to low it will do that.

__________________
R. Downs
1985 500SEL (260,000 miles) SOLD!
1974 280 SOLD!
1994 Volvo 850 Turbo Wagon (Yuppie Ice Sled)

"I know I have a Benz and they know it too." If you start bragging about it or shoving in people's face, you then become a Wally; especially to the girls.