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08 Silverado Overheating!!


Rubicon500

Question

Last week, i ran into a store to pick something up and i left my truck running as my wife was sitting in it... came back and noticed that the engine temp was higher than normal!!

 

Once i started driving, it returned back to normal operating temperature. Since then, i have been keeping an eye on my temperature gauage. My observations have been that while driving the temperature is reading as it should, idling at a stop light for a couple minutes are fine, but when it's idling for 5-10 mins it starts to get hot. This problem has NOT resulted in a check engine light.

 

I have an 08 silverado with the 4.8L, and 130,000kms

 

I have never cleaned the throttle body on my truck, so i'm going to do that tonight.. as my idle bounces around quite a bit.

 

Could the thermostat require replacement?

 

Any help with other things to check to narrow down the problem would be much appreciated!!

 

Thx!

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Thank you for the info everyone

 

I had another observation tonight. My truck was parked on the street for 5 hours, I went to start it up and instantly the temp gauge was up at lesst an 1/8.. In other words it was telling me the engine wasn't cold.

 

The engine temp should be cold after 5 hours shouldn't it?

 

Maybe my gauge or temp sensor isn't working properly?!?

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I can confirm that my fans come on when the AC comes on, as well they come on on their own when necessary without the AC. My coolant level is good. There are no signs of leaks in the system anywhere. Visually the rad doesnt appear to be that dirty.

 

I got the same high temp reading on the gauge tonight, but even when its in park and you get the RPM's up to 2-3K the temp gauge starts to cool back to 210.

 

Tonight i also cleaned my throttle body, and my RPM's are stuck at 2k while in park. It triggered code P0507.. high engine idle. It now requires a re-learn.. and from what i hear it can be programmed or i can drive it for a while and it will correct itself.

 

Is it possible it's the thermostat? If not, i don't know what the possible problem could be... everything else seems fine. It probably wouldn't be a bad idea to get a coolant flush...

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Another update... on my way to work it started getting hot again.. so i pulled over opened the hood.. and the fans DID NOT come on.

Then i turned on the AC and they did, and it started to cool.

 

So, for some reason the fans won't come on, on their own. Temperature sensor??

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I had the same concern with my 2011 crew cab 4.8, after doing much research On this and another forum I came up this (copy and paste)

 

THE PCM commands the low speed cooling fans on when engine coolant exceeds 220 degrees. The PCM commands the high speed cooling fans on during the following conditions: engine coolant temp. exceeds 220 degrees and a\c refrigerant pressure exceeds 265 psi. If the fans don't come on at the temp. check the temp sensor or relays out.

 

I believe its normal for your truck, I mean think about it when at idle no air is passing through the radiator ( with that efan set up) the coolant has to reach a certain temp for the fans to kick on, or the ac has to reach a certain psi, with the ac on its hardly ever going to go past 210 due to the fact that fans cut on and off constantly, a member on this forum mentioned to me that a tune can control/change the temp at wich your fans come on. I hate efans I'd much rather have a clutch fan, that way there is always air being pushed through the radiator, just my two cents.

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Another update... on my way to work it started getting hot again.. so i pulled over opened the hood.. and the fans DID NOT come on.

Then i turned on the AC and they did, and it started to cool.

So, for some reason the fans won't come on, on their own. Temperature sensor??

 

 

When I'm actually driving my fans hardly ever come on unless the ac is on, only time the coolant temp pokes past 210 is when idling for a while.

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well, after more observation...jdelrizzle was correct. My truck is behaving properly.

 

I was waiting for my wife once again, idling with no AC, and the temp started creeping over 210 again. Since i know my fans turn on for sure with the AC, i let it keep creeping. Eventually my fans did come on and it cooled it back to 210. I guess this is something i've just never noticed before, because i knew while driving it was ALWAYS 210, so shouldnt it be when idling? anyways.. i was wrong and learned something new.

 

thanks everyone for your help!

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Maybe so but why the F would I sit in my truck in 90 degree weather without ac on? I don't have that much time on my hands to play around to see. When I'm comfortable in my truck, heat on in winter and air on in summer, my trucks all hold tight at 210 or just shy.

 

You say your truck does not fluctuate when idling with the a/c on. I suggested that if you wanted to see what the OP was asking about it would require you to sit with the truck idling without the a/c on. Did not ask you to do that as a normal condition all the time. I see the OP has posted that what I suggested did in fact reproduce the issue he reported. If you would have tried it, you would see the same thing the OP saw. You chose to not want to try due to (what I can only think) the fear of sweating. Does not matter now, OP is happy with the answer he got, and even tried what was suggested to replicate his issue.
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Check the fans - sounds like they're not working.

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Could be anything - crappy motors, loose connection in wiring, really low on coolant, or bad temp.sensors.

 

If I remember right, one kicks on before the other - so the sensor for each fan will have a different kick-on temp. ... or the computer controls them (more than likely these days).

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No problem. Let us know what you find - keep us posted.

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Just because the engine temp is higher than normal does not mean it is overheating. When it overheats it will push hot antifreeze out of the engine, into the overflow bottle, then once that is full, it goes to the ground.

 

It is normal for temp to fluctuate when the truck is just sitting there idling. The hotter the day, the more often it will heat up then cool down. If you have the a/c on, the fans should be running all the time (that the compressor is engaged) when stopped with engine running.

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