66 coupe sometimes too hot

[RobJones]

Drove the vette (66 coupe 427/425) to a car show today about 25 miles away. It ran just fine all the way there it ran about 150 degrees the whole way. When I got there I had to go through the little town, and then sit in line a little whille. It then jumped to about 210 & released steam through the expansion tank when I shut it off. Then it ran fine al thw way home & then got hot again once I got into town. Where do I start, fan clutch? Thansk Rob Jones

 

[6T7Redvette]

Maybe a simple fix

You might want to check your engine idle. If it is too low you may not be drafting enough air through the radiator to get enough heat transfer.
Sometime if you just rev your engine a little to 1500 you should be able to cool things down very easily. Remember when you were growing up and the cars from the sixties were overheating in traffic jams, people would just rev the engine to get more cooling.
Good luck.

 

[Midyrcoupe]

Drove the vette (66 coupe 427/425) to a car show today about 25 miles away. It ran just fine all the way there it ran about 150 degrees the whole way. When I got there I had to go through the little town, and then sit in line a little whille. It then jumped to about 210 & released steam through the expansion tank when I shut it off. Then it ran fine al thw way home & then got hot again once I got into town. Where do I start, fan clutch? Thansk Rob Jones

Expansion tank? Does this car have a small block radiator? That might be some of the problem.

Another tip: Use the fan from a '70 A/C car (7 blades with aggresive pitch) along with a heavy-duty fan clutch form Pep-Boys, et al.

 

[Gerry]

I thought BBs did not come with expansion tanks. Am I wrong?

Best regards,
Gerry

 

[RobJones]

Expansion Tank?

I guess it is not a expansion tank but just a pressure release valve on the bottom of the radiator.

 

[Midyrcoupe]

Sounds like the drain petcock?? If it's leaking/steaming from there, go have it checked at a radiator shop.

 

[rwd]

You might double-check the coolant level. An air bubble in the cooling system would do that.

 

[IH2LOSE]

Rob did you try and tighten the pet cock?

where its leaking.

 

[SG4206]

I would install a 20-24 lb. radiator cap to stop the boil over. Then research the cooling problem.

 

[IH2LOSE]

I would install a 20-24 lb. radiator cap to stop the boil over. Then research the cooling problem.

Sorry to disagree SG4206

I would not suggest this higher lb radiator cap because it is only a band aid at 20 to 25lbs pressure have may have hose'e blowing off or burst a radiator.

Find the real problem and correct it.update us on whats happening

 

[SG4206]

IH2LOSE-
That is my point. The higher cap will show the weakest link. Be it hoses,clamps or radiator tubes. I want my cooling system to have the 25 lb. capability;not just 12 lbs.

 

[JohnZ]

Sounds like it's just "puking" through the overflow hose that runs from the filler neck down to the bottom of the radiator on the passenger side; if it's coming out of the drain petcock, that's another issue.

If it cools fine on the highway but heats up in slow traffic, it's a low-speed airflow and/or timing issue; make sure the radiator is sealed properly to the rad support (foam seals), the shroud is in place, and the fan clutch is working correctly.

The '66 L-72 had "ported" vacuum to the distributor (no vacuum advance at idle), which contributes to idle overheating; tee the distributor vacuum line into the short hose from the carb base to the choke pull-off diaphragm (which sees full manifold vacuum) and that will make a significant difference.