I have an'81 240D that is my daily driver from Marysville to Boeing Field. While she has 295T the car has always received very good care by mechanically adept owners (I am the second owner) and runs beautifully.
Except- when it rains quite a bit after a few miles the brakes will act as if the pedal is “hard” or fading and it takes longer for the car to stop. If I hold my foot (medium to light pressure) on the brake for a few moments, there is a barely perceptible pull to the right-then the brakes return to their normal good stopping ability.
The problem may not occur again-not even if I go through a mud puddle. This only occurs when it rains and we’re talking a steady rain! It never occurs with dry pavement or simply moist pavement (fog, misting etc.).
When I had the front end aligned and new shocks put on last week they inspected my pads and rotors and reported them as good. Brake reservoir is up (just flushed and replaced with new MB brake fluid the week before) and the wear light is not showing. Tires are those recommended by MBNA and good. Vacuum system is working just fine with no apparent problems.
So, what is causing this?