Hello, all. Brand new to this forum, as I've been out of MB ownership for a few years. (used to have a 250C) I'm thinking of picking up an old MB for my kids to drive this winter. (in lieu of the MG Midget they drive in the summer)

I drove a '78 240D last weekend. Runs well, minimal rust and I'm thinking of pulling the trigger. However, when test driving, the power assist to the brakes was clearly not working. When braking, the pedal was very hard and high, requiring much pressure to stop. After coming to a stop, the pedal would soften up and go down, but the next stop would have the same hard pedal.

In my minimal research, it appears that the brake booster may be shot, but also that other thinks could cause this problem, such as vacuum pump, vacuum line check valve, etc. Any thoughts based on the described symptoms? Brake booster replacement doesn't seem too bad, but is there a worst-case scenario?

Additional info: I read (after the drive) that vacuum problems that affect the brake booster can affect the ability of the engine to shut off with the key. I can't remember if I actually turned the car off after the test drive or just left it running. However, when talking to the owner yesterday about the brake situation I asked him if he has any trouble getting it to shut off and he said no.

Thanks for your help.

-Scott