Cooling issue

[03GMCYukonXL]

Ok so back story incase it matters.

I have a 2004 Tahoe that had a slight coolant leak. The coolant was low one summer and it slightly over heated. Not too bad. (It wasn't me driving it).

So the issue I have is this. When it's warmer outside, 70 degrees +, the temperature will climb to about almost 3/4 the way up but ONLY when climbing a hill and then coming to a stop. It will never go higher than that. And when I start moving, the temp will go back to normal. Again, this is only when it's above 70 out. The truck will idle just fine and the temp gauge will stay one tick below the half mark. Always. When it's cooler outside. 60 and below, it will not do this. NEVER. The gauge cluster is accurate because it has been hooked to a reader and the temps matched.
Things I have done,
New water pump
New thermostat
Coolant flush
Parked on a hill and let idle for 45 minutes with the coolant cap off to eliminate air bubbles

So, I'm down to thinking it's either the clutch fan, or partially clogged radiator. The reason I don't think it's the clutch fan, is because it will idle just fine with no temp increase. I know that doesn't eliminate the fan being weak at higher RPM with a heavy load on the engine.
The reason I'm thinkin it's the radiator is because that seems to be the most logical answer . I've read that overheating can clog them somehow, and the guy who had it before me mixed different antifreeze colors which I've also heard is bad.

This is the AI search results. I've eliminated air in the system, Thermostat, and water pump. I can replace the coolant temp sensor I suppose but the temp reading is accurate so I see no need.



Most Likely Causes & Solutions:

• Radiator Clogging (Internal/External): The radiator is likely clogged with debris between it and the A/C condenser, or has internal sediment reducing flow. Solution: Clean between the radiator and condenser, and perform a thorough cooling system flush or consider a radiator replacement.
• Faulty Fan Clutch: The fan clutch is not engaging to provide maximum cooling when the engine gets hot under load. Solution: Test the fan clutch (it should roar when the engine is hot) and replace if weak.
• Stuck/Failing Thermostat: A partially stuck thermostat cannot open enough to handle the increased heat demand. Solution: Replace the thermostat, preferably with an OEM part.
• Air in System: Air pockets trapped in the cooling system (often after a repair) can cause heat spikes. Solution: Perform a proper cooling system "burp" to remove air.

 

[Fless]

Haynes has a test to determine if the fan clutch is engaging. Note that we've heard of aftermarket fan clutches that cause excessive noise/roar so, when replacing, use OE if available. If not available new, a junkyard unit might be a good choice.

Section 4:

 

[Doubeleive]

most likely it is indeed the radiator in the past I have had the exact same thing happen to me and after the 1st time I already knew to just replace the radiator and problem solved.
** I will add use a oem or good name brand quality replacement. If you go with the cheapest thing out there then expect more problems such as the return line being too large and sending too much coolant back into the reservoir tank.

 

[Doubeleive]

also if by some really Weird chance you have the 28" radiator you can change it to a 32" easily the wider mounting holes are present on all frames and all you need other than the wider radiator is the wider fan shroud which can be found in practically any junk yard. The fan is the same in either case.

 

[03GMCYukonXL]

Thanks guys. I so happen to have a whole ass 2003 Yukon in my personal bone yard. Has a know good fan clutch and radiator....So as soon as the Avalanche is fixed, it's in with the Tahoe.

 

[LsHart]

Where this at?