CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Leaking overflow tank?

Is it normal for a small amount of antifreeze to leak out of the small hole on top of my Jaz overflow tank? This is on a 73
Chevy small block.

If it was overfilled to begin with, it is normal. Or it could indicate that there is a blockage in your radiator. Do you have any overheating problems? If not, keep an eye on it. If you are really concerned, change the coolant.

Temp is normal. I opened the cap and the coolant is pretty high, about an inch from the top.

If you begin with the radiator topped off to overflowing and connect the overflow hose to a reservoir which has water just covering the outlet, when the engine heats up the water expands and the excess goes to the reservoir where it remains until the engine cools. When cool, the water contracts, causes a vacuum and returns to the radiator. If the overflow reservoir is not original, how high is it mounted relative to the radiator cap? Does the radiator cap relief valve open freely? Does the cap seal and hold pressure?

The overflow tank has two markings on its side: full and low, or equivalent. It appears you filled the tank well beyond the top mark, so some overflow is to be expected. If you remove some coolant, that ought to solve your problem.