2000 Tahoe 5.7 will not reach 195* please help

[andrewlolney]

Hello all,

 

I have a 2000 tahoe with a 5.7L. I just picked it up last Saturday and for the life of me I cannot get it up to operating temp. I've replaced the T stat with a brand new 195, replaced both ETC sensors, changes the coolant and burped the air our twice. I have good heat but will slowly lose heat at idle....which sounds like a bad t-stat...

 

Also I'm ignoring my gauge in the truck as it reads 20* cold. I am getting a live ECU reading from my OBD2 code reader at 183.3*F. To verify my findings I started up my old GMC, let it warm up to temp and took a reading of 195.5*F so I know my code reader is accurate. Not sure where to begin. It's been 32*F here in MI even with it cold out the truck should still reach operating temp as my GMC does.

 

I really dont want to mess with blocking off my radiator as I should never have to...its not a diesel.

 

Any and all help will be greatly appreciated.

 

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[Jsdirt]

If you're getting good heat out of it, I wouldn't worry about it.

 

If you threw a scan tool on 10 brand new trucks, I guarantee you'd walk away with 10 different readings. The sensor is probably off a bit. A handheld infrared thermometer should be fairly accurate if you want to know the actual engine temperature.

 

If it is indeed too cool, you'll want to remove the t-stat again and inspect the thermostat housing for pitting, damage, or built-up gasket material. Anything that allows coolant to divert around the t-stat will significantly lower the operating temperature.

 

Back in the day, I had a '78 Cutlass that would never get over 140° on the mechanical gauge in the car - I had milky white oil traces on the dipstick from top to bottom, and inside the oil fill cap. Ended up being the cheap, pot-metal aftermarket Mr.Gasket chrome t-stat housing had pitted from electrolysis, and had grown wide enough to completely bypass the t-stat, without leaking a drop outside of it.

 

If that checks out ok, return the t-stat and get another one - it's probably defective. But before you do that, look at the temperature stamped on the base of the t-stat (brass part usually). You may have got a misboxed one that's a 185° unit instead of a 195° unit.

Edited December 27, 2018 by Jsdirt

[ronrymanr]

Was it a private seller? How many miles on O.D.? The Answers to your temperature issues will benefit me too[emoji223]

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[andrewlolney]

Ok I will take a better look at the housing tonight after work. My concern with it not heating up is all of the condensation inside the motor will not dissipate and my fuel mileage will be down as the motor isnt warm. I will look into that better tonight. Is this a common problem with these motors? I've had LS for the last 10 years and this is my first 5.7L so this is a little new to me.

And thank you for the response!

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[andrewlolney]

Was it a private seller? How many miles on O.D.? The Answers to your temperature issues will benefit me too[emoji223]

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Dealer. 99k miles. Rust free from VA. They told me the gauge was wrong... so they didn't lie entirely. Lol

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[Jsdirt]

I wouldn't say it's common, unless it has a chrome housing. Some of those are super-cheaply constructed and will become a sacrificial anode. I've owned many 350's, and only had that issue on the Cutlass.

 

I'm betting on either the wrong, or a defective t-stat. You could throw it in a pot after removing it to test it on the stove - see what temperature it opens at, then use that info as ammo if it is indeed wrong for when you return it.

[ronrymanr]

Awesome thanks. Lets agree that there will be no more issues[emoji223]

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[kickass audio]

Is your fan spinning faster on the truck than the other one? It may be pulling in a little bit more air to make it cooler but I highly doubt that is the case. When you installed the thermostat did you get an OEM one or aftermarket and did you drill a tiny hole on the outside edge of the thermostat just inside where the gasket seats so you can let a tiny amount of coolant bypass the thermostat and get all of the air out of the system? I had a problem on a newer engine where an aftermarket t-stat worked fine for a year and then was sticking open slightly and eventually set off a check engine code for the engine not getting up to temperature. Your truck is older and I don't think they had that listed in the OBDII as sensitive as the newer vehicles for in inefficient engine not running at operating temps. My dads 97 tahoe ran at 180 all the time and only would get around 190 in the summer if he had the air conditioning on full blast and it was over 90 degrees outside. 

 

What is the condition of your radiator fluid? Is the radiator and overflow tank filled with sludge? You could also be having issues from a build up of scum in the system and that usually contributes to running hotter but I have seen a small number of times where you run a tiny bit cooler than normal.

[andrewlolney]

Is your fan spinning faster on the truck than the other one? It may be pulling in a little bit more air to make it cooler but I highly doubt that is the case. When you installed the thermostat did you get an OEM one or aftermarket and did you drill a tiny hole on the outside edge of the thermostat just inside where the gasket seats so you can let a tiny amount of coolant bypass the thermostat and get all of the air out of the system? I had a problem on a newer engine where an aftermarket t-stat worked fine for a year and then was sticking open slightly and eventually set off a check engine code for the engine not getting up to temperature. Your truck is older and I don't think they had that listed in the OBDII as sensitive as the newer vehicles for in inefficient engine not running at operating temps. My dads 97 tahoe ran at 180 all the time and only would get around 190 in the summer if he had the air conditioning on full blast and it was over 90 degrees outside. 
 
What is the condition of your radiator fluid? Is the radiator and overflow tank filled with sludge? You could also be having issues from a build up of scum in the system and that usually contributes to running hotter but I have seen a small number of times where you run a tiny bit cooler than normal.

No both fans sound about the same. Not any louder than the other. And no I've never heard of drilling a whole in the t stat- I've changed quite a few and have never done that. I usually put an aspirin in to hold the thermostat open to let coolant through. Then it dissolves and closes. Lol. The Resivoir and coolant both look great. Coolant looked like it was changed when it was traded in.

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[txab]

So this truck has been converted from a clutch fan to E fans? Do the fans stay off or run all the time

[mikedeezxxx]

I think your tripping out for no reason. 32 degrees outside and 195 temp on the gauge is not bad. I have a Trailblazer SS w LS2 6.0 that will stay at 185 temp. It does have electric fans and 160 degree thermostat. Either of those temps are perfectly fine. I’d say the only other thing you could change is the coolant temp sensor that’s screwed into the engine block. If it still stays at a low temp, I say just drive it and enjoy. Don’t worry about it.


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[Hillwood]

If you are losing heat at idle, the heater core might be partially plugged.. Flush it out good by taking the hoses off and flush both ways..

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[andrewlolney]

So this truck has been converted from a clutch fan to E fans? Do the fans stay off or run all the time

No, sorry for the confusion. I was comparing the fans between 2 trucks. Both are mechanical clutch fans. Sorry about that.

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[andrewlolney]

I think your tripping out for no reason. 32 degrees outside and 195 temp on the gauge is not bad. I have a Trailblazer SS w LS2 6.0 that will stay at 185 temp. It does have electric fans and 160 degree thermostat. Either of those temps are perfectly fine. I’d say the only other thing you could change is the coolant temp sensor that’s screwed into the engine block. If it still stays at a low temp, I say just drive it and enjoy. Don’t worry about it.


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My issue is I have a brand new 195* thermostat in it. I'm not getting over 183* I've replaced the coolant temp sensors. And still get the same reading. My other truck rides at 195* on the nuts. My worry is it's not even cold out and I cant get it to operating temp. So when its 0* outside I'm thinking it will run colder yet... so I'm trying to trouble shoot why I cant get the temp up. I know it's not wrong but it's not right either when every other 5.7 I've ever worked on rides at 195 on the dot and this one won't. And yes I replaced the sensor for the gauge as well.

Thanks for the reply.

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[Black02Silverado]

It seems to me that the thermostat isn't working, new doesn't mean it is good.  Best bet is like stated above.  Either pull that one out, or get another one, put it in a pot of water and see at what temp it opens by the time the water boils.  Then you know for sure the T stat is good.

[andrewlolney]

It seems to me that the thermostat isn't working, new doesn't mean it is good.  Best bet is like stated above.  Either pull that one out, or get another one, put it in a pot of water and see at what temp it opens by the time the water boils.  Then you know for sure the T stat is good.

I did get another new one last night. Haven't had a chance to put it in yet. But yes I will put them both in water.

Thanks.

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