On my '65 Dart with a stock /6 I am having slight overheating problems. The engine was fully cleaned, including water passages, about 40,000 miles ago, along with a new radiator and heater core. The radiator cap is, I believe, 12 pounds and I'm living at 4000 feet.

The problem is I can't keep the radiator full of coolant. It likes to run almost 2 gallons low, I can fill it up and within a mile of driving it will drain that coolant out of the overflow. The temp gauge barely rises above its "normal" area, where its been the last 40,000 miles, yet if I leave it running for a minute it will sometimes boil the coolant in the radiator, and if it is still full it will proceed to dump coolant all over the ground.

Am I suffering a clogged thermostat or is there a bigger problem here?

Thanks

Caleb

Are you sure the pressure cap is working properly? The pressure cap is suppose to help give the coolant a higher boiling point. I don't know with you being a 4000ft if you need a higher pressure rating? maybe someone else may know the answer. If everything is working right(pressurecap,thermosat,waterpump,fan), you may have a small leak somewhere. My daughter's car is having that problem. But it only does it on hot days. With summer almost here I need to get her radiator fixed.

_________________
87 D-100 /6

I'm think head gasket or cracked cylinder head.

Gases from a cylinder are getting into the cooling system under pressure and forcing the coolant out of the system.

Run without cap. Fill it up and see if you're getting bubbling out of the radiator (should happen cold).

Also do a compression check to see if a cylinder is way out of line with the rest.

It's not actually boiling if it's a leak into the cooling system, you're getting combustion gases.....

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

It's possible you've got a combustion gas leak (e.g. bad head gasket), but I agree with Herbhill, the pressure cap is the first place to look. The correct rating is 14 lb, not 12 lb. You don't need a different rating because you're at high altitude. However, high altitude makes the cap's condition more important, for water boils at a lower temperature as altitude increases.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

For reference, I ran it with the cap off and had no noticable bubbling.

I'll work on getting a cap in a couple days and see what that does for it.