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Discussion Starter #1
So I changed my thermostat and now my truck is overheating, even when I just let it sit there and run. Any ideas on what it could be? At this point I'm getting pretty tired of dealing with it. Might just take it to a shop & see what they get me for or even rid of it. AGHHH!!!!
 

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maniac mechanic
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Did you use premixed coolant or mix it yourself to refill as well? If that mixture is off and you have too much coolant it will overheat.

As long as that is good, like he said run it with the cap off. Check the thermostat you bought and make sure they gave you the correct one as well.
 

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So you installed a new thermostat.

Is it truly overheating or running hotter than normal.

With the new thermostat it will run over the half way mark.

Worst case air in the system.

Why did you change the thermostat.
 

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Not to question your intelligence, but what is your definition of overheating?

I ONLY ask that because it is common for the temp gauge to display a hotter reading after a tstat change because the tstat spec was changed by GM.

Well, this is only true depending on your model year. Early model years have a lower spec and I have to ask this because you didn't specify your model year.

Can you elaborate a little on what brings you to the conclusion it is overheating?
 

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Discussion Starter #6
Its overheating. However I used the premixed coolant I got at an auto parts store. Soooo my last resort is be gonna be to drain the coolant and put some new one in, I'll also run it with the Cap off. Any suggestion on which one I should buy? BTW thanks fellas! I'll let you know how it goes.
 

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It should not overheat because of incorrect coolant mix. Especially if you are sitting idle.

Since it was not overheating before the work, I'd start with retracing your steps. Overheating is a result of poor flow or a bad cooling fan. Or Bad water pump. Or closed thermostat. If the new thermostat is stuck closed, it will overheat. A water pump that doesn't flow enough coolant will allow the vehicle to overheat. A slipping fan clutch, or belt, will not draw enough air through the radiator.

Did you test the new thermostat prior to installation?

Running the vehicle with the cap off will only work if you are very low. As the coolant warms it will expand and overflow. What I used to do is keep it low on purpose. Let the vehicle run. You'll see the coolant rise in the radiator, but soon thereafter the thermostat will open. At that point I top off and place the cap on the radiator.

Did you notice any sludge build up on the underside of the radiator cap? Dexcool gets sludgy when air is introduced (possibly by a leak). Often times, the cooling system becomes very inefficient due to a high sludge content.
 

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Discussion Starter #8
Its an 04 four cylinder. & yes its definitely overheating my temp gauge is almost all the way up.
 

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Discussion Starter #9
I changed my thermostat cause my temp gauge needle was stuck on cold. No I did not test my thermostat b4 I installed it. Stupid question but how would I test it?
 

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Its an 04 four cylinder. & yes its definitely overheating my temp gauge is almost all the way up.
Well, that does not mean much, to be honest.

Does it stabilize or do you shut it down before you hear warning chimes and dash lights indicating it has overheated?

I always forget. After 3 years of being corrected you'd think I would remember the real numbers but I think the new thermostats are 15 degrees hotter, from 180 to 196. That's probably wrong.....But something like that. Somebody will be able to share the correct numbers if I am incorrect.

And since the gauge is calibrated from the factory to match the 2004 thermostat spec, a result is the gauge reads high, because in reality it is hotter than previous. It just so happens the needle position is alarming to us because it appears differently.

Not saying there is not a problem. However what you are describing has been described by many many others. One way to know with absolute certainty is to read the coolant temp via the computer. I do not believe a code reader will do that. You can drive it to a shop (if you feel comfortable driving it) and have them read it with an infrared tool.

But many of us have an Ultragauge or ScanGauge. I actually purchased the Ultragauge when I got my truck for the specific reason of reading coolant temp because I wasn't convinced the needle position was accurate.

In addition, the gauges between your truck, my truck and somebody else's truck can absolutely vary. Not just because of model year, but because that's just what happens. For the most part they are stable, but it isn't too uncommon to find a variance of needle position between two vehicles.

Lastly, you can purchase a hydrometer for cheap at the parts store. That is meant to read the specific gravity of the coolant. It will tell what what the freeze point and boiling point of the coolant is. This can be useful to help determine what your mix ratio is. If you have an overwhelming amount of water, or coolant the hydrometer may help indicate that.

I have no idea about this web page, it is meant as a reference only so you know what you will be looking for should you go for the hydrometer. Totally not necessary, but it is an option.
VALUE BRAND Antifreeze Hydrometer, Disc, Professional - G2506655 at Zoro
 

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I changed my thermostat cause my temp gauge needle was stuck on cold. No I did not test my thermostat b4 I installed it. Stupid question but how would I test it?
Sorry, I was writing when you posted this one so I'll answer separately.

There are no stupid questions.
To test the thermostat, you use a pot of water and bring it to a boil and read the water temp. If nothing else, this can test to ensure it does actually open, never mind the actual temp that it begins to open.

I only asked that because if it was tested prior to installation, then it should not be faulty. Given what I wrote in my previous post, I'd like to see you follow up on that before you pull the thermostat again.

Also, I do not recommend testing this one in a pot that you plan to boil your green beans in. :)
 

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Discussion Starter #12
I will definitely keep you guys posted once I find the resolution to this madness. I'm hoping I can figure this out without taking it to a shop, I'll feel like such a failure. We're supposed to have a "snow storm" here in OKC over next couple of days so it might just be a day or so b4 im able to get my hands on this thing. Thanks for all the helpful suggestions & like i said I'll follow up with you guys when shes back to running like normal.
 

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Run it by a shop one day and ask them to check the temperature for you. I really think you're making more work for yourself than necessary. At least then you will know if there really is a 'problem'.

Or let it run until the needle appears to be stable and post up a picture for us to see where it's sitting at the high setting.
 

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Discussion Starter #14
Alright guys I got my truck back yesterday, and turns out it was just a faulty thermostat! Thanks for all help, just glad to have DD back!
 

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Alright guys I got my truck back yesterday, and turns out it was just a faulty thermostat! Thanks for all help, just glad to have DD back!
That sucks, but it happens!

So the lessons learned here are!

1. you did the job right......part failure
2. now you know how asking a question here works..........many members with different views or explanations of a said topic
 

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I agree with Ed there.

I've had my Scan Gauge II since 2005, its been a great tool to have. Being able to read codes and delete them on the fly is nice too
 
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