Hello. Today I took my 250sl out and the brakes felt really hard ... like non-assisted brakes but even harder ... scary. The brakes felt pretty decent last time I drove it, not excellent, but decent ... this change is sudden. I assume it's not the master cylinder as it didn't feel spongy. I searched and have read quite a bit on this forum about failed Boosters and the common test seems to be that I should see a RPM increase when I press on the brake pedal and this is not happening ... no change in RPM.
I did the test of pressing the pedal a few times, than holding down the pedal and starting the car and the pedal is supposed to push down farther once started ... it did not.
I'm looking for help on how to confirm it's the booster. Could it go bad suddenly, without much warning? The RPM when cold seems normal and after warm up drops to normal.
I have a later 250sl ... and would appreciate any advise on some tests to confirm the fault. At the moment I happen to be in Southern California and if it turns out to be the booster I can take it to Power Brake Booster (Bell Gardens, California).
Would appreciate any advice.
Thanks
Oz