Symptoms:
Hard brake pedal and no power brake boos at startup. I have boostafter about a minute of driving,but lose it if I pump the brakes to stop.
Trans shifts normally if I baby it from a stop butslips/flares if I step on it..Trans fluid level is OK.
Vacuum gauge shows ~15in a idle directly off of the vacuum pump. Anotherpost regarding an '85 300D said vacuum was ~21.
Door locks work. Testing with Mityvac, vacuum holds steady on circuit feeding inside the car and the power brake booster.

Questions:
1. What should "normal" vacuum read off of the pump?
2. Do these symptoms indicate a bad vacuum pump?

THX in advance,
Jack W

 

the vacc pump on this engine m617 is pretty strong normal vacc should be upward of 22hg' min. but these cars are old and rubber crackes over time as with many other componets in this car . remember that this cars uses a vacc. resivor which stored vacc. for aux acc. like central locking plus that sys only uses around 5-10 hg' to operate . i would start cheepest first . check for cracked vacc fittings(the 3,4 way rubber splitters found under the hood ,),check the main vacc supply hose from vacc pump lt front engine to brake booster you should be reading min. 22hg' amx is around 28-29 hg' with 30 being perfect ofcourse altitude plays a part higher up less vacc. i would begin there the main supply hose i see the lock collar loose causing alittle leak but enough to create weird problems