Has my thermostat gone out??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

saulgoode · 11-09-2015, 11:01 PM

Hey guys!

Anyone want to take a shot at diagnosing an over heating issue.

2006 5.3 w/ 200,000 miles.

Regular running temp 210-220

Recently It has started to creep up to 225 then surge to close to red line (260) then the fans kick in and bring it back down to around 210.

This only happens in stop and go traffic or stop lights, and has been increasing in frequency.

I have been noticing this for a couple of weeks, but never get to full on over heating.

Today in heavy traffic it was doing this a lot 225 then surge to 260 then fans then back to 210. I was a little concerned so I kicked the heat on full, it would blow HOT for maybe 5min then nothing but cool air.

All signs point to thermostat in my opinion.

Any thoughts?

Mr-Jack · 11-10-2015, 02:15 PM

pull the thermostat and put it in a pan of water and heat it up, see if it opens and closes...if not, you might want to check your pump

1FastBrick · 11-11-2015, 07:48 PM

The Low speed on the electric cooling fans have most likely gone out.

Get it up to temp and watch the gauge as it passes 210. See if the 1 low fan ever comes on before both fans turn on in high speed.

Other wise you need a scanner with Bi-direction controls that can cycle the fans to see if this is the issue.

11-09-2015, 11:01 PM	#1
saulgoode Registered User Join Date: Dec 2003 Location: Houston Posts: 388	Has my thermostat gone out??? Hey guys! Anyone want to take a shot at diagnosing an over heating issue. 2006 5.3 w/ 200,000 miles. Regular running temp 210-220 Recently It has started to creep up to 225 then surge to close to red line (260) then the fans kick in and bring it back down to around 210. This only happens in stop and go traffic or stop lights, and has been increasing in frequency. I have been noticing this for a couple of weeks, but never get to full on over heating. Today in heavy traffic it was doing this a lot 225 then surge to 260 then fans then back to 210. I was a little concerned so I kicked the heat on full, it would blow HOT for maybe 5min then nothing but cool air. All signs point to thermostat in my opinion. Any thoughts?

11-10-2015, 02:15 PM	#2
Mr-Jack Beer Drink'n Knuckle Dragger Join Date: Mar 2010 Location: Eatonville, WA Posts: 493	Re: Has my thermostat gone out??? pull the thermostat and put it in a pan of water and heat it up, see if it opens and closes...if not, you might want to check your pump __________________ GOD BLESS MY BROTHERS & SISTERS THAT SERVE WITH US *- 67 GMC Long-Wide* *350/SM420* *My BACON Wrapped Meatloaf Recipe*

11-11-2015, 07:48 PM	#3
1FastBrick Registered User Join Date: Jun 2014 Location: JunkYard Posts: 48	Re: Has my thermostat gone out??? The Low speed on the electric cooling fans have most likely gone out. Get it up to temp and watch the gauge as it passes 210. See if the 1 low fan ever comes on before both fans turn on in high speed. Other wise you need a scanner with Bi-direction controls that can cycle the fans to see if this is the issue.



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