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Heater doesn't work.Engine overheats at higher rpm but drops back down at idle.

(2005 Chevrolet Tahoe)
in Lawrenceburg, TN on January 17, 2012
Could the heater core be stopped up? should I try flushing it?
Displaying 1 answers & 4 comments
Popular Answer
on January 17, 2012
Sounds like you have a bad thermostat. Is there no heat at all times? Feel your radiator hoses one should be hot and the other should be warm after the veehicle reaches operating temperature. Also check if your cooling fan is turning. I believe you have a clutch fan which means as the vehicle gets hotter the fan turns faster.
on January 17, 2012
Yeah there is no heat at all..It did tease me for a second the other day and blow warm.But just as my hopes got up it went cold again.I have checked both hoses going into heater core and only one is hot.
on January 17, 2012
Does the cooling fan engauge? Is there sludge build up in the coolant resavoir? If there is sludge visable, the heater core may be clogged as you suspected. A clogged heater core will not cause the vehicle to overheat. If the Thermostat dosnt open the coolant wont flow through the radiator causing it to overheat. If you want to verify the heater core is not plugged remove the coolant hoses from heater core and connect a garden hose over outlet and back flush. I know its cold out but this may be the only way to check the heater core is operating properly. I should say this is the only way i know if it is clogged other then checking the hoses at heater core. Im starting to think you may have two problems but i could be wrong. Did both problems begin at the same time?
on January 18, 2012
The fans are running and I don't notice any sludge.The heater stopped working first.I didn't notice it overheating until I had some of the gauges fixed that were not working.The temp gauge was working fine so I didn't have them touch it.Seems wierd right??Fix one thing and find another problem,lol..
on January 18, 2012
The temp gauge usually dosnt go out on these clusters only the speed odometer and theres another one but i cant remember witch one. I didnt think of this earlier but the cap on the coolant resivoir may be faulty. The cooling system is supposed to stay at 15 pounds per square inch (psi). You may have a faulty resivoir cap instead of a bad thermostat. Sorry i didnt think of it earlier. Heres a web site i found that backs up my ideas of what your problem may be so you dont think im just throwing things out there.
If you still have this problem you may want to repost your question to Repairpal so someone else see your question again and can give you more input. Its been a while and once someone answers a question it seems like others dont want to give input. Thats just my opinion but nothing toward any of the other users on Repairpal.
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