My 1981 300td w123 has been running great ever since I dug it out of a snowbank 6 months ago. I normally only take it 15mins to work and 15mins home 5 days a week. I dont think I've ever gone so long without even one tiny little problem.

Yesturday I drove it 2 hours on the highway. About halfway through my trip the brake pedal started sinking to the ground. The car still stopped normally buy I had to push down way further than I'm used to. So I pumped the brakes a little and the pedal came up again. But then the pedal was stuck up. When I braked the pedal would only go down a tiny bit and it was way harder to stop the car. I had to really use some force to get the car to stop. When I parked the car, the engine wouldn't turn off so I had to pop the hood and push the lever. The engine not turning off hasn't been an issue for about three years when I replaced the fuel shut off valve and disconnected the leaky doorlocks, and blocked off the vacuume to the engine with a golf tee. Why would the brakes act up at the same time as the engine? On the way home I was sitting at a stop light with my foot on the brake, the pedal was still raised and wouldn't sink when I pressed down, and suddenly I felt the pedal sink down to the normal level and the brakes felt perfect the rest of the way home. When I got home the engine turned off without a problem. What the heck is going on? I am not a mechanic and probably have no buisness owing such an old car, but I'm in love with it so any suggestions would be greatly appreciated!

__________________
1981 300TD Wagon