Am currently having problems with my brakes in my 1984 300TDT. The car has strong brakes on the 1st pump but on the 2nd consecutive pump, the brake pedal gets stiff & I loose brakes.
I have a relatively new brake booster & newly rebuilt vacuum pump. Current vacuum at idling 20-22 and increases as the accelerator is pressed. I tried to plug the 2 small vacuum stems connected the main vacuum hose from the vacuum pump to the brake booster, but to no avail... still stiff brake pedal on a consecutive pump. Thus, eliminating all possible leaks from its branches, the leak source possible involves the vacuum pump, brake booster, and/or the main vacuum line. Can anyone help me with this? Can the main vaccum hose be the culprit?
- Tippee
84 300TDT
84 240D
84 230E
66 250SE

your brake booster might be bad but i would bet that it is the check valve on the top of the vac pump. probably broken. if it is make sure you get all the little pieces out.