My car overheated recently?

1996 CHEVROLET LUMINA

140,000 MILES • 6 CYL • FWD • AUTOMATIC

MSHELDON85

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my car overheated recently, i checked it out and noticed the water pump was leaking. i replaced the water pump yesterday. i filled the radiator. i let the car run for a little while and it over heated. from a cold start it is only taking about 5 minuted to start to get really hot. the upper hose gets really hot alot of pressure, the lower hose only gets a little warm with not so much pressure. i was thinking head gasket but there is no sign of coolant in the oil. any ideas?

Jan 25, 2010 at 3:31 PM

SQM

CAR REPAIR CONTRIBUTOR
6,383 POSTS

Hello,

The issue you are describing sounds like a stuck closed thermostat. When a thermostat fails at closed position, it will prevent coolant from flowing thru the engine. This will crate a temperature difference between the two radiator hoses, one will be hot and another relatively cool.

https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat

I have attached the thermostat replacement diagrams for your reference.

Please let me know of any questions.
Thank you.

Images (Click to enlarge)

Sep 22, 2021 at 9:50 PM

Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.