[Solved] 2000 Yukon XL high operating temp

[ryanguy426]

Solved -- Mix of bad thermostat, air in the cooling system, and a leaking top radiator hose at the water pump side. Reseated the hose and tightened the clamp, replaced thermostat, bled the system for an hour, and truck hasn't gone above 214°F for 4 days as of this edit. Thanks everyone!

2000 Yukon XL 1500, 5.3

Truck loses coolant with no leak, not in oil, no white exhaust. Non Castech heads (pulled valve covers and verified). Already replaced water pump. Rad not leaking.

Truck gets to 230F sometimes, going up hill on interstate or sitting with the AC on in a drive thru or in traffic/city driving. "Hot coolant" hasn't shown on the dash yet. Scan tool verifies 232F at the most so far since I started tracking it.

Supposed to drive on a 1300mi round trip road trip mid August, this temp gauge is making me nervous though. All my other vehicles have held 210° perfect. Is this normal for these trucks?

 

[OR VietVet]

The combination of the "truck losing coolant" and the higher temp, IMO, means something is not right. Is it running hotter when the coolant is low? Does it run hot if coolant is full?

How do you know there is no coolant in the oil? How do you know there is no leak? Just because you don't see coolant on the ground? Pressure tested when warm and cold?

 

[ryanguy426]

It runs hot pretty much no matter what.

I also put cardboard underneath my truck when I parked it for a few days, and there was never anything but a small oil leak dripping onto it that I already have known about since I bought it.

I say there's no coolant in the oil because I have checked the oil and it's not milky, I've also changed it and didn't find any water/antifreeze in it when I caught some inside of a cup. Oil looks as fresh as it did the day I put it in there a month or two ago.

I haven't had the money to rent the pressure tester yet, I just had to replace the fuel pump. I'm doing it next week to see if it holds pressure. I was wondering if there was anything common that I could check besides what I already listed. Somebody suggested I checked their heater hoses on the firewall, but they're dry and they weren't leaking.

I drove the truck to work today, when I turned it off a small amount of antifreeze came out of the overflow bottle and into the parking lot. I never noticed that before. That's the only other thing I've noticed recently

I guess the next thing to do is wait for my money to come in and pressure test it? It runs great as if nothing is wrong otherwise. Just weird.

 

[Hobert]

Could be faulty thermostat.? Not opening soon enough building pressure and blowing out the overflow

 

[OR VietVet]

Exactly what I was thinking when he says it runs hot no matter the fluid level and now he sees coolant puking out of the reservoir. Then I also remember he said he replaced the water pump but did not mention the thermostat. I think what is being puked out is the coolant loss and I would also check the fan clutch for proper operation and I would also remove the top cover and check for ANY debris at any cooler in front of the condenser, the condenser itself, front and back and same on the radiator.

I used to live in the country and driving around out there has more debris floating in the air when you get around pastures and fields. Can still get crap in the city but worse in the country.

 

[treehan77]

Borrow a pressure tester from autozone, advance or something. Wry well can be ******* out coolant and burning off without it ever hitting the ground.

 

[ryanguy426]

So I took off my fan shroud and I sprayed out the back of the radiator with my garden hose, and the entire bottom of the radiator essentially, all of the fins are bent. Probably a quarter to a half of the fins on the bottom of the radiator are all bent. I'm assuming that's a source of my problems, but I will still report back after I can afford a pressure tester.

If it's the radiator, I read online that we can upgrade to a 34 in by just replacing the fan shroud with one from a 2500. The clutch fan can stay as is, correct? (Not jumping the gun on replacing the radiator, just curious)

 

[OR VietVet]

You can also, maybe they are still around?, get a fin comb and straighten them. I have done it before. You also need to get in between and look at the front of the radiator and both sides of the condenser.

Is there any play at the fan clutch? Does it spin smooth? Does it spin freely when cold, like free wheeling, or close to it? When warmed up it should be harder to spin.

If fan clutch leaks you should see it and feel a film at the front center of the clutch.

 

[ryanguy426]

You can also, maybe they are still around?, get a fin comb and straighten them. I have done it before. You also need to get in between and look at the front of the radiator and both sides of the condenser.

Is there any play at the fan clutch? Does it spin smooth? Does it spin freely when cold, like free wheeling, or close to it? When warmed up it should be harder to spin.

If fan clutch leaks you should see it and feel a film at the front center of the clutch.

Yeah, the fan clutch is smooth and I don't see any leaks or anything on it. It's definitely harder to spin when warmed up, it doesn't spin 100% freely when it's cold... is it supposed to? Like if I spin it as fast as I can it won't go a full rotation. It's loud coming from a stop, but It quiets down above 2000 RPM. Not loud at idle. I assume this is all normal, all of my clutch fan vehicles have been like this, including my two current GMT400 trucks. Fan clutch is a Hayden 2744.

The condenser looks fine, there were some leaves and some bugs in it that I sprayed out. I don't really see any bent fins on the condenser. The radiator fins are bent on the front and back though. Wtf.

 

[OR VietVet]

That fan clutch sounds just fine. The radiator not so much for air flow. Pics? How much area on the radiator, front and back, has bent fins?