Engine Overheating

2004 CHEVROLET IMPALA

87,000 MILES • 6 CYL • FWD • AUTOMATIC

JDSHARP1983

MEMBER
1 POST
FOLLOW

I am at loss as to what is wrong, I have checked everything I know of. Here is what I do know. Engine is overheating. The coolant is not leaking. Radiator when cold, has plenty of coolant. When engine get hot all the coolant seems to be draining into the coolant reservoir. Top Radiator hose is getting warm. Lower Radiator hose is staying cool. Heater is intermittent, doesn't always blow hot. When is blows hot air the engine doesn't overheat. When it doesn't blow hot the engine gets hot. Sometimes there is an awful screeching noise when I start the car. I just replaced the Blower Motor. GM shop said it was going bad. They said since it was going bad this could cause the heater to not work properly and could cause the engine to overheat since the blower motor was not properly pulling the heat out of the engine compartment properly. Still no heat, but the AC blows really well now...lol...and the engine is still overheating.

I can only think of 1 or 2 problems.
1. Water Pump is going out..screeching noise.
2. Thermostat is stuck closed.

What do you guys think? thanks

Dec 18, 2008 at 10:05 PM

SQM

CAR REPAIR CONTRIBUTOR
6,383 POSTS

Hello,

It does sound like you might have an intermittent issue with the thermostat sticking.
As when the thermostat works correctly the engine does not overheat, and you get warm air for the heater, since the hot coolant is flowing through the heater core.
And when the thermostat gets stuck closed, the engine overheat, and you get cool air thru the heater, since the hot coolant is not flowing through the heater core.
When an engine overheats you will get the coolant overflowing to the reservoir.

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

The screeching noise could be the water pump. Might have a internal failure to the pump.

https://www.2carpros.com/articles/water-pump
https://www.2carpros.com/articles/symptoms-of-a-bad-water-pump
https://www.2carpros.com/articles/water-pump-replacement

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.

Images (Click to enlarge)

Aug 10, 2021 at 7:43 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.