300 CD vacuum problems
 

1984 300 CD no power brakes and unable to shut off. On again off again problem.

checked the vacuum hose connections by the oil filter as had the shut off problem berfore.

It might be time to rebuild the vacuum pump. Search the Diesel archives.
Gently pull off one of the hose by the brake booster line - see if you have any vacuum there. If you don't, there is a rebuild kit, and after 1/2 a day, you will be stopping and locking your doors again.

If the vacuum loss is intermittant, it could be a check valve(s) going bad (they are insided the vacuum pump)