Well, that is interesting. I did not know that you could pump up the brakes with a bad master cylinder and it would hold pressure. But that is good news. How would I confirm the diagnosis? What should I look for? I still have brakes - the pedal does not go all the way to the floor - but it takes a lot of pressure to stop. I can actually drive it some if I am careful but it is not safe.

Does anyone have a good master cylinder 1981 300SD. Is it much trouble to replace? Do you still need to do a bench bleed?

Thanks.