08 Silverado Overheating!!

[Bilco]

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!!

[Swede]

Are your rad fans coming on?

[shadowstang]

I Would Change The Thermostat Anyways And Check Coolant Level Also Maybe Air In The System You Never Know Also Like Swede Said Check If Your Fans Are Coming On

[motorboat]

CLEAN THE BUGS OFF THE FRONT OF YOUR CONDENSOR AND CHECK THAT YOUR FANS (IF ELECTRIC ) ARE SWITCHING ON. When you start driving the air starts moving through your condensor and rad, thus cools.

[Bilco]

thanks for the tips guys!
I'm gonna look into it tonight

[JohnDeereMan]

yup, engine fans should be running with the air conditioning turned on... if not there is a problem.

[Bilco]

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...

[motorboat]

Condensor may look clean from front but pull off the upper closeout panel and look between the rad and condensor.

[JohnDeereMan]

engine fans run ,so that is good. if you have a pressure washer, wash the rad out really good, and when you think it is clean , wash it for another 5 minutes- trust me rads are funny that way.(dont bend the fins with the pressure washer). then let it dry up a bit and go for a ride- if it still runs hotter than normal, replace your thermostat. and yes it is very posible that it is your thermostat.
cheers

[oldccm]

well, this is a topic dear to my heart as my 04 Dodge has had every overheating issue known to man. so here we go: Did you check to make sure your rad is full? My resevoir was, but my rad was down a quart. Which turned out to be head gasket. Also this depends whether fan is electric or not, but if not does your fan clutch engage? Mine didn't Fan ran, but never engaged. Also is your rad clogged? I tried to drain mine and it was clogged like a SOB. Or it could just be thermostat.
My guesses from most probable to least are
1. Thermostat
2. Dirty Rad
3. Fan Clutch (if applicable)
4. Plugged Rad
5. Water Pump
6. Head Gasket

Good Luck

[diehard]

sounds like the clutch fan is not working right...but the high idle could be temp sensor is failing telling the ecm that the engine is cold and then picks the rpms up to warn the engine up but if you put the computer to it i think that would of gave you a code ? when you shut the truck off when hot do you hear the coolant boiling in the radiator ?

[Bilco]

thanks for all the info guys

My truck has electric fans...

I had another observation last night. 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?!?

[oldccm]

Depends where it was parked and at what time of day. If it was sitting on the street in the sun a 4 in the afternoon that would be normal. If it was 6 am that would be a different story. Good luck

[Bilco]

5 to 10pm last night

[motorboat]

GM has had STICKY gauges in the past. Clusters were replaced in some trucks 2003+ i believe.

[oldccm]

I'd say that's normal. You are probably hyper sensitive to the temp gauge lately. I know I am. It should have read cold this am, I'd use that as your gauge, with the warm weather it's not uncommon for the coolant to remain slightly warm. I'm starting to think it could be a clogged rad or hose. I'm not familiar with electric rads are they 2 stage or just 1? Let us know what you find out

[boakley]

Originally Posted by Bilco

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...

could it be the flow rate your water pump is putting out at idle?

If you can find out the spec. on what it is supposed to put out then pull the top rad hose and test flow and compare to what the spec is.

I had an older outboard motor that the pump did not leak but at slow speeds impeller was bad enough that the flow just wasn't up to snuff. But at speed it was still good enough to keep the engine cool.

[motorboat]

Does it ever actually touch the RED on the gauge? If it's less than 75% on the gauge i would consider that normal temp range. When you run at idle with a/c on in 35c weather things tend to run warmer with no airflow through the rad.

[Bilco]

well, after more observation...My truck is actually behaving properly.

I was waiting for my wife once again, idling with no AC, and the temp started creeping over 100 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 100. I guess this is something i've just never noticed before, because i knew while driving it was ALWAYS 210 with or without AC on, so shouldnt it be when idling? anyways.. i was wrong and learned something new.

thanks everyone for your help!

[four_420_twenty]

when sittting in a parking lot idling your truck can get warm. no flow threw the rad and plus when ac is on motor is working a bit harder, i know when i kick mine on in my car my rpm drops a bit.