08 Silverado Overheating!!

Knowklew · August 21, 2012

Be advised, the dummy gauge on the dash is highly inaccurate. The 210 mark on the gauge is actually more like 192-196. The lower and higher marks on the gauge are even more irrelevant. My scan gauge tells me the real temps and the gauge on the dash is far from reality.

Rubicon500 · August 21, 2012

thanks for the info everyone.

it's gone no where near the 260 level.. and not puking at all.

my resevoir is a bit low... but there's still lots in it

The reason it's concerning for me is that i've never noticed it to be over the 210 mark.

i'll check the fans tonight, clean the throttle body because my idle has been low and rough... and see what happens.

desrtrat · August 21, 2012

another tip.. if you have a air compressor, blow out the radiator core from the engine side out. start at the top and work your way down to the bottom real good, than flush out good with water hose..if no compressor just use water. you be surprised at what can come out. dirt, leaves, bugs, all sorts of crap. i do mine once a year due to all the dust living in the desert. helps a lot on keeping things cool...

good luck..

also- do your AC/trans/oil coolers also..

Rubicon500 · August 22, 2012

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...

Rubicon500 · August 22, 2012

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??

jdelrizzle · August 22, 2012

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.

jdelrizzle · August 22, 2012

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.

Rubicon500 · August 22, 2012

I agree... The theory makes sense

But, it just never used to behave like this. It was always on 210 and never moved!

jdelrizzle · August 22, 2012

It's not a theory, I wish one of the gm techs would chime in.

Doug_Scott · August 22, 2012

I agree... The theory makes sense

But, it just never used to behave like this. It was always on 210 and never moved!

When you say it starts to get hot, how high does the temp go? 210 is not high, coolant will not boil until about 270 degrees with a working rad cap. What is the weather like in your area? Around here it has been a very hot and humid summer, truck is running warmer than it did in the early summer when temps were more normal.

Personally, I would not be too concerned as long as it does not actually overheat. Let the truck idle in the driveway for a while, with the a/c off, and see if the fans ever come on. They should, eventually. I have not seen my truck not turn the fans on when the a/c was on. High side pressure gets real high, real fast, with no air flow through the condenser. Without the a/c on, it will be normal for the temp to get to a point, the fans come on, the temp drops, the fans turn off. The gauge inside the truck will rise and fall with the fans cycling.

SouthCo · August 22, 2012

All 3 of our GM's (03 Tahoe now sold, 05 Yukon Denali XL, and Sierra 5.3) all held engine temp at 210 or just shy of it. Regardless of outside temp. Winter freeze or summer heat and we have seen 110F days this summer. I routinely sit and idle in the 2010 Sierra 5.3 with a/c blowing for 20 minutes while my wife grocery shops when it's 90-110F. Thay way it's cool for the groceries and the temp gauage holds tight at 210 or just shy of it. Electric fans and all... They work fine.

Doug_Scott · August 22, 2012

All 3 of our GM's (03 Tahoe now sold, 05 Yukon Denali XL, and Sierra 5.3) all held engine temp at 210 or just shy of it. Regardless of outside temp. Winter freeze or summer heat and we have seen 110F days this summer. I routinely sit and idle in the 2010 Sierra 5.3 with a/c blowing for 20 minutes while my wife grocery shops when it's 90-110F. Thay way it's cool for the groceries and the temp gauage holds tight at 210 or just shy of it. Electric fans and all... They work fine.

With the a/c on, the fans will run all the time, and the temp will stay about the same. Try it without the a/c on. My truck sitting with no a/c on, 90 outside, the temp will fluctuate about a needle width or two, with the fans coming on and going off. Turn the a/c on, fans run all the time, temp stays constant.

SouthCo · August 23, 2012

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.

Rubicon500 · August 23, 2012

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?!?

Rubicon500 · August 30, 2012

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!