It overheats 1 per month ( every 1000 mile s) becuse its low on coolant. I add a about a gallon when it overheats.

 

When you refil coolants, it gets pushed back into reservoir bottle and overflows, coolant doesn't get sucked back from reservoir which is confusing to me....?..

 

Why doesn't coolant return?

 

Thank you so much for advice!

 

Is this the diagnosis for the head gasket?

Coolant isn't returning to the radiator because it's being displaced by air. The air doesn't allow the system to draw the coolant back when it cools, it usually just sucks the radiator hoses flat.

 

With the engine running check in the overflow res. for a constant strea of bubbles rushing in. That's your head gasket allowing combustion chamber pressure into the cooling system.

The best definitive diagnosis is to use a leakdown tester. When you find the cylinder(s) with the gasket failure, bubbles will start pushing out of the radiator.