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Brad, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2366
Experience:  ASE Certified Master Technician
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98 chevy lumina: overheating..The coolant..cooling..leaks

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my 98 chevy lumina keeps overheating. The coolant keeps backing up into the reserve and overflowing instead of going into the car and cooling it. I cant see any kind of leaks from anyplace on the car whatsoever and i dont know what else to do. Would it help if i flushed the radiator?
HelloCustomer and welcome to!

I'm thinking that most likely you have one of two different things going on here.

The thermostat may be stuck in a closed position, not allowing coolant flow through the engine resulting in an overheat. Once the coolant starts to boil, it will blow out of the overflow tank due to excessive pressure.

You might also have a blown head gasket and/or head, allowing exhaust gases to enter the cooling system. This will usually cause the coolant to back up into the tank long before the engine starts to overheat (but eventually causing an overheat condition as a result).

I will warn you that this engine is not very tolerant of an overheat. It usually only takes once or twice of the gauge going into the red to cause damage and warpage of the cylinder heads.

You need to have your cooling system checked for the presence of Hydrocarbons (an emissions gas) to verify the integrity of the cylinder heads and head gaskets, and if they are proven to be bad I highly recommend engine replacement.

Good luck!
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