Engine overheating?

MCSHANTI666

MEMBER
2005 CHEVROLET IMPALA
6 CYL
FWD
AUTOMATIC
157,000 MILES

I bought this car used this past december so im unfamiliar with the history. The car seems to be blowing cold air and overheating but once in a while it will blow hot air and then the temperature returns to normal. I topped up the fluid in both rad and reservoir and tested it a few times raising the temp and letting it cool down.I thought it had fixed the problem but when I took it out for a drive it overheated again after a bit and never recovered. Could this hopefully be just the thermostat? Or something more serious?

Sunday, April 18th, 2010 AT 5:23 PM

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

There are few reasons for this to overheat in the manner you are describing.
It could very be the thermostat, however when you have a stuck closed thermostat the temperature will keep rising until something catastrophic happens unless you shut off the engine.

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

You could also have a issue with the cooling fan. Check to see if the fans come on.
A non functional fan can be the cause of a faulty motor or relay. The relay is located in the junction box under the hood (see below for diagram).
The relay can be tested.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

You might find these articles helpful:

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works
https://www.2carpros.com/articles/replace-electric-fan-motor

Another possibility is a faulty water pump. If the water pump does not cycle coolant thru the engine it will overheat as well.

I have attached the fan and water pump replacement diagrams for your reference.

Please let me know of any questions.

Thank you.

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