1999 GMC Yukon Coolant Temp Guage fluctuates erratically.

1999 GMC YUKON
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RICH JOY
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Engine Cooling problem
1999 GMC Yukon V8 Four Wheel Drive Automatic 165K miles

For a week now the temp guage on my truck's display has been fluctuating suddenly and spontaneously. The cabin heater also stops blowing HOT air when the guage goes to max.

I checked: coolant level - good. Upper radiator hose - warm/hot with good pressure. Hose to heater core - warm/hot.

Any thoughts as to what is causing this?
Have a great day!
Nov 18, 2009 at 9:00 PM
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RASMATAZ
  • ✓ASE Certified Mechanic
  • 75,992 POSTS
  • ASE Certified Mechanic
Replace the thermostat and test the coolant temperature sensor.
Nov 18, 2009 at 9:07 PM
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