Already time for a cooling system rebuild.

Update:

Drove the Dart to work yesterday, determined to change the belts. Took surface streets except for the last bit which was I-440 at about 60 mph. No problems.

On my lunch break, I went across the street to a NAPA store and had them match up a set of belts. The alt/AC belts were a little shorter, but that was the closest they had. Started on the car after work. Found out I didn't have enough room to move the alternator and get the NAPA belts on. Even took the alternator off to see if I could get it under the belts and then bolt it up. Nope!

Something I neglected to mention earlier is that the alternator was replaced who-knows-when with a later metric unit. By "metric" I mean the bolt on the alternator that goes through the slide part of the bracket is an 8mm with a 10mm head. While I had the alternator off, I noticed that there is another threaded hole along that same radius that would allow the alternator to be adjusted out for longer belts. So I cleaned the threads, got a new bolt out of the parts bin with a 13mm head, added a wide washer and a spring washer, then put it back together with the AutoZone belts I bought last week. The power steering belt from Napa fit, so after that was finished I cleaned up and drove home.

Decided to take my normal interstate route home and the ambient temperature was 90, so I figured it would be a good test of the Prestone flush. Wasn't aware of any problems until the large hill just before my exit. Was doing 70 up that hill and something just didn't feel right. Exited just after the crest and could hear the radiator cap moaning from the pressure. While waiting for a chance to turn off the ramp, steam was visible at the other end of the hood. I cranked the heat up all the way and drove it gently along the backroads the rest of the way home. No more signs of steam or complaints from the radiator cap the rest of the way.

I'm thinking my next step is a new thermostat, and if that doesn't help a new aluminum radiator from Summit.