I recently got a 1965 I6 coupe. Everything is stock but has an aluminum 2-row radiator (very clean looking). I did not see any corrosion or rust inside the radiator.

I drove the car to work almost a week ago for the first time. I was 5am, so the weather was cool. The gauge was reading a little on the cool side. About 25 miles into the drive, I start to lose power, so I pulled over. Stream started to pour out.

I towed the car home. I refilled the radiator to see if the car starts and look for leaks. Started fine and I could see no problems. I ran the car about 10 miles with no problems. With the car at operating temperature, I removed the radiator cap...came off easy...wasn't hissing at me.

I expected to see the fluid circulating inside the radiator, but it seemed not really to move.

The next day I replaced the thermostat. I tested both old and new, and both opened at around 190 degrees. Put the new one on, and I still did no see too much movement of fluid after 10 minutes of running.

There was not leak at the water pump, nor did it make any bearing noises. I figured maybe the "propellers" weren't working. I bought a new pump. When I took out the old pump, it looked also okay and appeared to function appropriately.

When I went to put the new pump on, I could see whoever put on the old pump had stripped one of the holes and tried to re-thread the hole in the block and did a lousy job. The bolt would only go in 2 turns and the threads were corroded.

I decided to let professionals fix this and it's at the shop...and it's going to cost $400 to fix it!!! 3-4 hours at $100 per hour.

Besides the fact that this is very expensive, what ideas do you guys have regarding my overheat problem? If it's not the thermostat, then it is more than likely the water pump?

 

a) That a lot of friggin' money to chase a few threads and install the pump. A 5/16-18 tap costs under $10.



b) It is extremely UNLIKELY that a "bad water pump" will cause overheating. Bad bearings in the pump will make noise, and a bad seal will leak, but it could be falling apart and still pump coolant.

Look for clogged tubes in the radiator, improper routing of the heater hoses, and built-up crud in the block and head. Consider using a better fan, and fan shroud.