wro87

WE have a 71' coupe with a 350. I have filled the radiator to the top of the filler neck several times and each time after a couple of drives we find that the level has dropped about 2" in the top tank of the radiator and the top hose no longer what appears to have no fluid in it. We have changed the thermastat with a 165deg and seems to have no leaks and the water tempis looking fine. Is this level normal we have seen somew moisture around the overflow house but remember this car has no overflow tank.

Thanks wro87

bobs77vet

2" sounds kind of low to me but 1" would not, why not put an overflow tank on it? the radiator will purge itself when it gets hot? what pressure rating is the radiator cap?

thegazman

Install a coolant recovery system and you'll be money ahead. The tank will collect your over flow when the engine heats up and recover it as it cools. Plus it will help purge the air out of your cooling system and provide better coolant flow as your radiator will be full to top.

gerry72

You are ignoring the purpose of the expansion space in the radiator and getting the predictable result. There should be a fill line embossed on the fill side of the radiator. If you go above this line with a cool radiator, when the system comes up to temp, the expanded coolant has to go somewhere, which is the purpose of the spit tube; to purge the liquid that exceeds the space it's confined to. On some Corvettes (pre-'73) there is a divorced expansion tank. The same rules apply here. If you don't leave the expansion space, it will just purge out the spit tube. Even on modern cars with closed cooling systems, there is a cold fill line on the expansion tank. If you over-fill these, they too will purge the excess coolant.

For the system to function properly (assuming the cooling capacity is adequate) you need the expansion space in the radiator and a fully-functional pressure cap of the proper design.

Easy Mike

Is your car an automatic? If memory serves, only the AT cars did not have a surge tank on the right fender skirt. For AT cars without the tank, coolant level will drop a little after filling and a drive, but should hold a consistent level after that.

Are you finding antifreeze on the driveway? White smoke in the exhaust?

Mike Ward

Excellent post.

7T1vette

Whether the radiator or an expansion tank, whatever has the pressure cap on it must have space for water expansion when it heats up. The '71 radiator has a cap (like mine); it needs at least 2 inches of air space in the upper tank to keep from 'relieving itself' after you fill it.

wro87

Thanks gang!! Looks like I will not worry about it as much since we don't have an expansion tank and I just don't think I need to put one in. Seems like the space left in the tank just might be what the doctor ordered.

wro87

7T1vette

It's what the design engineers expected, anyway.