Question about 2005 GMC Sierra
1989 GMC C1500 5.0L V8 - after replacing the thermostat twice and the temp sensor, still have this problem and not knowledgable enough to resolve - please help! after running for a bit temp will rise (temp guage indicates) to ~195 deg (thermostat rating) and then after (I assume) the thermostat opens the temp will drop to ~160 and stabilize there regardless how long or hard the engine is run... I am at a loss... I do have a higher cooling capacity radiator than the one that came stock but wouldn't think that was an issue as I thought the thermostat should still regulate the block temp. regardless... I haven't tried replacing the radiator cap but will tonight... is there any possibility that the cap is allowing the system to overpressurize and not allowing the thermostat to close once opened?... just grasping at straws here... please help! I am having the same exact problem on my '05 gmc sierra. It has always ran at about 190 - 195, i noticed today that when i started the truck (already warmed up) the temp went to 190. Then after about a minute or so, it drops to the bottom temp of 160 and stays there. Does this sound like the thermostat is bad or is the gauge / sending unit going bad?
Check instrument voltage stabilizer, also if alternator over charging will do it.
Posted on Jan 19, 2009
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Posted on Jan 02, 2017
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