My 1980 300D has a vacuum issue. These are the symptoms.
When starting the car, after a half a minute the brakes feel 'normal'. After a short drive to the first stop sign at low speed, the brakes go rock hard - much pedal pressure needed to stop. after a drive of 1/2 mile, the brakes feel normal again during slowdown to 2nd stop sign, then they go rock hard again. If I accelerate quickly to about 45mph, if the brakes are used they remain hard as a rock. If I get on the freeway, after a mile the brakes are fine again if I only touch them once. Two applications and the brakes are hard as rock. I have replaced the diaphragm and cleaned the valves in the vacuum pump. At a stop sign the climate control will stop working if the brakes are applied. If the car is put in park at a light the climate control keeps working. I measured the vacuum at the booster - when the pedal is depressed vacuum drops way down. The booster is leaking, Yes? I'll replace it. But would these same symptoms manifest if the valves in the vacuum pump are worn out?
When starting the car, after a half a minute the brakes feel 'normal'. After a short drive to the first stop sign at low speed, the brakes go rock hard - much pedal pressure needed to stop. after a drive of 1/2 mile, the brakes feel normal again during slowdown to 2nd stop sign, then they go rock hard again. If I accelerate quickly to about 45mph, if the brakes are used they remain hard as a rock. If I get on the freeway, after a mile the brakes are fine again if I only touch them once. Two applications and the brakes are hard as rock. I have replaced the diaphragm and cleaned the valves in the vacuum pump. At a stop sign the climate control will stop working if the brakes are applied. If the car is put in park at a light the climate control keeps working. I measured the vacuum at the booster - when the pedal is depressed vacuum drops way down. The booster is leaking, Yes? I'll replace it. But would these same symptoms manifest if the valves in the vacuum pump are worn out?