I recently rebuilt my engine with all new cooling parts. The car runs below 200 ecept at highway speeds, when it will keep creeping up until it gets near the red line.

Being a heating engineer, I can't understand why it will idle for extended periods at normal temp, but run hotter the faster you go.

The other issue is that my new fan clutch squeels during acceration. Has anyone else experienced this. The new clutch has 1200 miles on it. I am replacing it as soon as possible.

Thanks in advance for any help.

I dumped the fan clutch (when it seized, in May)for a flexfan and haven't seen anything to the right of 200 all summer. 350 with heads, cam, intake, MSD, headers, etc. TH400. No A/C.

I have never heard of a fan clutch squeal,sounds like loose belts,new belts should be checked for tightness after some miles because they sometimes grow. make sure that there isn't any paint or crude in pulley groves

The squeal sounds like a bad bearing. Alternator? water pump? AC compressor?

As for the overheating on the highway it sounds like you are exceeding the cooling system's max capability. Possible culprits are a poor radiator, missing lower spoiler, missing fan shroud, collapsed radiator hose, or missing radiator support/shroud (these are VERY important) seals. You mentioned that you have new cooling parts, are ALL the parts new? Also, just because the part are new doesn't mean they are good.

Best of luck!

The faster you go ,the faster the pump pushes the coolant through the radiater,giving the coolant less time to cool off,if that clutch fan isn't engaged its not pulling enough cool air through.Try a flex fan,those clutch fans are not totally reliable,theres cases of them coming apart ,that gets really messy,it's not a pretty picture, Ron 78

Here is my expereance with a flex fan in a corvette. The first one was a big Flex-a-Lite on my big block, it lasted nine months before it threw a blade, I was luckey, it hit the shroud and landed on top of the intake manifold. The second one was a Summit"Hi-Perf"fan, it lasted two months, I was cleaning the engine compartment and I noticed cracks on the blades.If you are going to run a flex fan keep an eye on it, the constant flexing of the blades causes stress cracks on the blades even if they are stainless. I have never had trouble with a clutch fan,check for up and down movement on the bearing,if yours has the exposed spring make sure it doesn't have crude between the coils whenever you check the belts

At highway speeds the fan isn't doing anything, that's why it has a clutch.

Thanks for all the suggestions.

The fan clutch was definately the cause of the squealing. During acceleration it would squeal until it got up to speed.

I opted to dump the fan clutch and go with a direct drive flex fan. I thought it might be noisier, but it actually is less offensive than the orginal fan/clutch combo.

The car now is running well below 200 deg, and after a 12 mile run between 75-95 in rolling hills, it never went above 200.

Excessive speed of the water throught the radiator will not decrease the BTU's rejected by the radiator. I firmly believe that c3 corvettes do not have enough natural airflow at high speeds to allow for the fan clutch to slow down the fan speed. Cars like Chevelles and Novas have much more grill area, and get tons of natural air flow at high speeds.

I am planning to get actual air flow readings in the future and will post them.

Beardface

White 77. 350/350 hooker headers true dual exhaust