I have 2 problems, I beleive they may be related. My 1980 240D will not stop running when I turn the key off. I have also noticed the brakes get real hard if it idles for a long period of time, like sitting at a long light. If the Brakes are hard, that's when the engine will not shut off. If I have good brakes, and i turn it off, it stops running just fine. I'm sure it's vacuum related. But where do I start?