I had to replace the engine in my 1953 GMC 3 ton with a '66 292 from a bus. The original radiator had some plugged passages in spite of several flushes, so I rigged a second radiator in front. At first it worked fine, but it eventually started getting hot again. Turned out, the plastic fan I attached to the engine(metal one was too big) made the bolts go loose and therefore, the belt loose and stopping the pump. I had already ordered a new radiator, so I put that in. Removed the plastic fan, since I had added a dual electric fan from a truck. Though it was a 3 row and not the 4 I wanted, I wasn't going to be hauling at it's max capacity.
It was still getting too hot.
Recently I added back in the second radiator. While I was at it, I checked the timing. Good thing as it was off. (Advanced? Don't remember, looking from the front as you would for timing, it was to your far left.) I gave it another flushing as I noticed there was still rust flakes in it, despite a previous flush. Let it sit over night with rad flush, vinegar, and rust remover. Then I connected the garden hose to the rad, then the block at separate times. Let the water run for a while. After, I also added that 'water wetter' stuff. While testing, it got up to operating temp and seemed to stay there. Then I gave it a little gas and kept it there. Seemed to slowly creep up, so I didn't risk a test drive. During a previous drive, it seemed to go up slightly faster while accelerating. Makes sense, 'under load'. Though, the pump should be running faster then. After installing the second rad, I looked in it and the water was flowing, showing the pump works.
All I can think of is the fan isn't up tight enough to the rads, or that little plastic fan that was on the engine somehow made a difference? Also, I don't remember if I replaced the temp sensor when I installed the universal temp gauge. The rads never boiled over when it said it was as high as 240.
The engine runs and works great.
What do you think?
