My son has a 90 626 as a first car, got it from my grandmother. Runs and drives good, but the brake pedal seems real soft. Pumping the brakes with the engine off it feels fine. As soon as you start it the pedal drops down some. Not sure if it is booster or m/cylinder. Fluid is full and looks good. Could it be air in the lines? Tried pumping brakes with the cap off of the m/c, did not seem to help.

 

Go to page 49:

http://www.autoshop101.com/forms/brake05.pdf


In any case, replace the brake fluid completely.