Engine heat

MACKEY0029

MEMBER
1999 GMC SONOMA
4 CYL
2WD
AUTOMATIC
167,000 MILES

99 sonoma won't build engine heat. Changed the thermostat (195 degree spec), runs even colder now. Around 140, give or take. Radiator doesn't even get hot. Won't blow hot air into cab either. Bled the system and checked coolant levels. Suggestions?

Monday, December 13th, 2010 AT 7:04 PM

8 Replies

JACOBANDNICKOLAS

MECHANIC
109,700 POSTS

Remove the thermostat and check it. You may have gotten a bad one. If it opens too soon, the engine won't warm up.

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Monday, December 13th, 2010 AT 7:06 PM

MACKEY0029

MEMBER
5 POSTS

I thought that was a possibility. Wanted to do that as a last resort. What are the chances it is a bad one? Is there anyway to tell from just looking at the thermostat that it is defective?

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Monday, December 13th, 2010 AT 7:12 PM

JACOBANDNICKOLAS

MECHANIC
109,700 POSTS

To test a thermostat, you need to boil it in water with a thermometer that will show high temps. By doing that, you will see when the thermostat opens. If you go to the home page under do it yourself, there is a section that describes how to do it.

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Monday, December 13th, 2010 AT 8:16 PM

MACKEY0029

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5 POSTS

I'll give it a try. Thanks.

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Monday, December 13th, 2010 AT 10:53 PM

JACOBANDNICKOLAS

MECHANIC
109,700 POSTS

Let me know what you find.

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Tuesday, December 14th, 2010 AT 5:17 PM

MACKEY0029

MEMBER
5 POSTS

For the past couple mornings its been around 20 degrees. I've let my truck idle for about 5 minutes before going to work and its been warming up to appropriate temp while blowing hot air into the cab. I don't know why it fixed itself but let's hope it continues to run properly. Thanks for your help.

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Thursday, December 16th, 2010 AT 12:11 AM

JACOBANDNICKOLAS