Slight Overheating at 230 degrees

[Gossamer]

Ok....I am stumped

Waterpump - changed
Radiator - flushed
Thermostat - changed (3 times)
System has been burped of air

My 2002 Tahoe with 5.3 overheats. It does not do it until driving about 10 miles one way. It isn't guaranteed it will overheat however. About 80% the time it will.
When it does it, it never gets over 230 and even fluctuates back to just under 210.
If it does not go back to just under 210 I can get it to do so by turning on the heater at the #2 setting.
It can virtually go all day with the heater on and it will not overheat.

So I know water is flowing because it peaks at 230.
All 3 times I did change thermostat the results have been identical so I know the thermostat can be ruled out now.

Anybody got any good ideas or know exactly what is going on?

Thanks

 

[mizzouguy]

Does it overheat while at an idle/slow speeds and then comes back down at highway speed? I'm thinking fan clutch.

 

[Gossamer]

Does it overheat while at an idle/slow speeds and then comes back down at highway speed? I'm thinking fan clutch.

No, it does the same at either one.

I am wondering....can the clutch fan sometimes work and then not work as good?
I have had one that totally went out on a 1999 Silverado and you could tell it was bad by the roar noise it was making but the thought of it working sometimes and not as good has run through my mind.

 

[Scottydoggs]

when you go over 210 the clutch fan locks up and makes a strong fan sound. when its working right.

grab the fan blades, see if you can make it wiggle, push and pull the blade. if theres any play its life is over.

i went through 3 of them dumb fans in 100,000 miles. they suck. first two were under warranty, last time it went out i installed electric fans.

also try cleaning the rad and condenser if you drive dirt roads. dirt can pack the condenser and rad's fins and then you get no air flow.

i like to spray them both down with de greaser, then hose them out from the engine side out to the bumper.

 

[Doubeleive]

if the fan clutch is good then it's likely the radiator, yank and put a new one in, easy job and most radiator shops will have one for around $185.00, they get clogged up even if it was flushed and especially if it is the original one, while you are in there clean out all the crap that gets jammed between there and the a/c condenser, leaves and dirt and bugs get stuck in-between the two.

 

[Chubbs]

I wouldn't mess around with a problem like this come warmer weather. If you aren't seeing any signs of coolant loss just Go straight to a new DELCO clutch. If the truck still cannot maintain operating temp, spring for a brand new radiator.

You could always run a test on the coolant for exhaust gas before spending on new parts. I saw those on the bottom shelf of "specialty" or mechanics tools @ Oreilly Auto. GM will have a TSB with the MYs affected & symptoms, before you go chasing your tail. Just saying there are numerous reasons for temp-related problems. But if coolant fill-level hasn't dropped then the problem won't be a cracked cyl head or fittings where coolant loss is result.

sometimes a bad clutch is simple to diagnose but not always! I went through like 4 of them on a dif't vehicle and learned they won't always completely fail; just enough to have you scratching your head.

 

[Gossamer]

Well....the problem showed itself quite well.
It was the radiator. It finally split on the drivers side.
Gonna change it out as well as the fan clutch and the belts while I have everything off the front.

 

[6speedblazer]

check and or clean the fins of the AC condenser and radiator. they get so packed with bugs and road grime they contribute a lot to running warm conditions.

*edit- looks like it was solved already.

 

[01ssreda4]

I was just about to say the radiator, you had eliminated most everything else based on your repairs and observations.

 

[adventurenali92]

Hey guys sorry to revive an old thread. Trying to figure out why my coolant temps are running high, Justin from blackbear has told me to clean out the radiator fins. edit: is he talking about the grooves on the front of the radiator face, like behind the grille?!
2006 Yukon XL Denali with a 6.0!