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Coolant temp sensor?

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New User

Jun 22, 2018, 1:29 PM

Post #1 of 4 (494 views)
Coolant temp sensor? Sign In

The Mrs said her 2003 Chevy Tahoe Z71 5.3L engine was running warm. I told her I'd check it later. 3 days before I looked at it. Upon starting it, dash gauge was reading 225 degress ish. So I instantly thought coolant temp sensor. Ran down to store and bought a new one. Disconnected the lead to the old one (still screwed into engine block) and connected the new one. It's now just hanging free in engine compartment, and I turned key on again to see what gauge says, hoping it would read zero. Still showing just right of center.
Now what?

Veteran / Moderator
Sidom profile image

Jun 22, 2018, 2:11 PM

Post #2 of 4 (488 views)
Re: Coolant temp sensor? Sign In

When you disconnect the sensor, the reading defaults to -44°, if the needle didn't move when you disconnect the sensor more than likely you have a gauge problem...

The clusters from that time period had lots of problems with all the gauges....The only way I know to confirm this is to sweep the gauges with a scan tool (move the gauges from the lowest point to highest & back)....

if someone else has another test....I'm sure they will post it....

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 22, 2018, 2:49 PM

Post #3 of 4 (482 views)
Re: Coolant temp sensor? Sign In

? Unplugging it didn't change reading on dash? A or B - It's not that more likely some other or oil pressure gauge which one dropped out?
Trucks dag nabbit could have "extra cooling" package you need to know and at least have the right gauge sender. If you are electric fan(s) only and a needle for temp (different possible) it may be just fine and come down however hot it is request heat only and disable A/C and also try leaving that and use heat out defroster only.
Sidom: Were you thinking a CTS or sender for gauge only? I can't know which set up for each truck just that if only electric fans it might be correct and not stay at one spot only all the time no matter what barring super extremes and if that hot 225 if system is tight isn't near boiling point with a working pressure cap,


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 22, 2018, 3:23 PM

Post #4 of 4 (474 views)
Re: Coolant temp sensor? Sign In

You need to also remember, coolant temp sensors read coolant, not air. You can't just plug it in outside the engine and expect a reading.

It does sound like you have a gauge problem though. You really need a scan tool to see the actual temp the computer is seeing.


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