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99 Chev. Tahoe Temp Gauge???

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Oct 15, 2008, 11:49 AM

Post #1 of 6 (1188 views)
99 Chev. Tahoe Temp Gauge??? Sign In

I have a 99 Tahoe with 180,000 miles with the 5.7 V8. My temp gauge has been acting kind of odd lately. If I drive with no heat on and the temp turned to cool (but still on OFF), the temp gauge goes to normal temp while driving. If I turn the temp dial to HEAT or WARM or do this and actually turn the heat on, the temp gauge starts to go down and cool off. My truck has always showed the temp gauge at the same temp for years while driving, idiling, heat or A/C, now it's been doing this. Do I just need to replace the thermostat or is something else going on? It's running just file, but seeing a different temp than usual it what concerns me as winter is approaching rather fast here in MN!


Oct 19, 2008, 1:33 AM

Post #2 of 6 (1175 views)
Re: 99 Chev. Tahoe Temp Gauge??? [In reply to] Sign In

replace thermostat and do flush. make sure you use flush additives with the heater wide open this should take care of your problem.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 19, 2008, 6:53 AM

Post #3 of 6 (1167 views)
Re: 99 Chev. Tahoe Temp Gauge??? [In reply to] Sign In

Agree with T-stat and flush. I think what's happening is that thermostat isn't closing tight and some residual cooling is happening at the radiator unneeded AND with the added heat lost to heating interior the temp actually drops. Heater really is a mini radiator itself.

Good that you take notice of these things. Temp gauge should read the same spot year round with only the wildest ambient temp extremes make it nudge higher or lower within norms,

Long retired now

Anonymous Poster

Oct 19, 2008, 5:23 PM

Post #4 of 6 (1161 views)
Re: 99 Chev. Tahoe Temp Gauge??? [In reply to] Sign In

I think with the temp fluctuating i would also keep a close eye on the oil, at 240F these seem to cook intake gaskets. A bad ground can also drive your gauges wild.You may also want to check or replace the temperature sending sensor.

New User

Oct 20, 2008, 1:36 PM

Post #5 of 6 (1149 views)
Re: 99 Chev. Tahoe Temp Gauge??? [In reply to] Sign In

Thanks for the info. That's what I thought, but just wanted to double check. I have not replaced a t-stat in while. Any idea how much they run for price and installation? It has always read the same temp year round until recently with the colder weather here in MN and I had to turn the temp/heat on to WARM.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 20, 2008, 5:34 PM

Post #6 of 6 (1144 views)
Re: 99 Chev. Tahoe Temp Gauge??? [In reply to] Sign In

I don't know of a life expectancy for T-stats but we tend to toss them when we are in there for things and also needs to be removed for flushing.

This one if fairly straight forward and thermostat + gasket are resonably cheap and on the DIY list if that's you.

However - it's a good opportunity to check hoses and those aren't so cheap but don't short yourself. OE clamps are funky but can do with good plier assortment if your are handy or there's a tool that costs way 2 much for those.

Know that this 5.7 was known for intake gasket leaks and that's a job if not done yet.

Prices for labor: You just have to ask locally what they want for this service. Parts you can just Google your local outlets or call them. If you send it out the shop should get their own unless you have an agreement and shops do charge "list" price for parts but are taking responsibility for them too.

Suggestion: Keep it 50/50 anti-freeze which = -34F protection but it's really ok if it get colder overnite at just that and no more. The mix would only be slushy and not break parts if you do experience colder temps - we do in NH here routinely. Too strong isn't good for the next Summer's cooling needs. Also IMO forget DexCool (Gm's trademarked anti-freeze) and just used guaranteed universal lifetime anti-freeze now boasted by Peak for example and color doesn't matter. I'd still change it once in a blue moon anyway.

Stay warm. Already been in the 20s here west of Beantown,

Long retired now

99 Chev. Tahoe Temp Gauge???

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