Working through the bugs on a 1983 300CD that I bought earlier this week.

Two nights ago I took it around the block just as a test run and it ran pretty well until about 3 miles into our journey when suddenly the brake pedal got rock hard. The brakes still worked but not very well and I had to stand on them to get a response. I suspected vacuum and sure enough when I got home and got parked it would not turn off with the key (it previously had turned off with the key without any issues). I shut it off with the stop lever under the hood and called it a night.

Yesterday I fired it back up and the brake pedal was still too firm and it would not shut off with the key. While the car was running, I put a vacuum gauge on the two nipples attached to the main vacuum feed from the vacuum pump to the brake booster and sure enough I got a zero reading. I turned the car off and disconnected the main vacuum line from the vacuum pump and restarted the car. Suddenly there was full vacuum coming from the pump. I reassembled everything and now I have good brakes and the car turns off with the key as expected.

Driving around the block last night and initially the brakes worked fine. After a couple miles, the brakes got rock hard again but this time the car sputtered and died. I jumped it and it started back up, but died again about 100 feet down the road. I jumped it a second time and this time after about 100 feet, it started to chirp/screech extremely loudly and then died. I gave up and dragged it the rest of the way home behind my truck.

I was immediately thinking alternator with the fact that it keeps draining the battery and figured the screeching was the bearing going out in the alternator. So i took it off and had it tested at the auto parts store and their machine claims it is still good. Spinning the pulley sounds a little gritty but not horrible.

Any ideas?

Also, there are two grooves in the alternator pulley but only one belt. Is this correct or should there be two belts?

Thanks. I know there is a lot going on in this thread but I appreciate any feedback.