2000 Yukon XL Running Hot While Towing

[FlyboyTR]

We have an 00 Yukon XL/1500. No engine mods. We purchased it last year and have put 8k on it with a total of 181K It was well maintained prior to our purchase. The engine temp is usually reading around the 210 mark on the factory gauge...sometimes just slightly below. We are now noticing that when towing our pontoon boat the temps will hit the 3/4 mark on the gauge and has shown as high as 230 on the ScanGuage. This towing at approximately 50-55 MPH. Slowing down below 40 the temps will slowly drop on the ScanGuage but frequently drop instantly on the factory gauge.

This past weekend I was towing our small tractor on a 16' tandem trailer with ambient temps around 97. I did not have the Scanguage onboard. Sometimes during hard acceleration the gauge would quickly rise to the 3/4 mark and the next time it may rise slowly. On occasion the gauge would do the instant fall.

One odd thing I did notice was shiny silver particles in the coolant. I was looking in the overflow tank while squeezing the upper radiator hose to move the coolant around. That was when I noticed it. I guess it's possible someone may have added some type of stop-leak, but that is not indicated anywhere in the extensive records I have. Could this be a water pump impeller coming apart? Although, the particles appear to be somewhat suspended in the coolant.

I am a bit perplexed as to where to start first, thermostat, drain and flush, water pump, fan clutch, sensor, wiring...?? Any guidance and suggestions would be greatly appreciated. Thanks!

 

[Rivieraracing]

We have an 00 Yukon XL/1500. No engine mods. We purchased it last year and have put 8k on it with a total of 181K It was well maintained prior to our purchase. The engine temp is usually reading around the 210 mark on the factory gauge...sometimes just slightly below. We are now noticing that when towing our pontoon boat the temps will hit the 3/4 mark on the gauge and has shown as high as 230 on the ScanGuage. This towing at approximately 50-55 MPH. Slowing down below 40 the temps will slowly drop on the ScanGuage but frequently drop instantly on the factory gauge.

This past weekend I was towing our small tractor on a 16' tandem trailer with ambient temps around 97. I did not have the Scanguage onboard. Sometimes during hard acceleration the gauge would quickly rise to the 3/4 mark and the next time it may rise slowly. On occasion the gauge would do the instant fall.

One odd thing I did notice was shiny silver particles in the coolant. I was looking in the overflow tank while squeezing the upper radiator hose to move the coolant around. That was when I noticed it. I guess it's possible someone may have added some type of stop-leak, but that is not indicated anywhere in the extensive records I have. Could this be a water pump impeller coming apart? Although, the particles appear to be somewhat suspended in the coolant.

I am a bit perplexed as to where to start first, thermostat, drain and flush, water pump, fan clutch, sensor, wiring...?? Any guidance and suggestions would be greatly appreciated. Thanks!

Sounds like you are indeed confirming that your trucks temp is indeed ramping up. Might be time to at least do a coolant flush as well as changing out the thermostat and possibly the water pump! Any signs of coolant leaking at the bottom of the water pump through it's weep hole?

 

[livingez_123]

Do you hear your fan engage as the temps go up? also sounds like you might need a water pump if your getting metallic particles in your coolant. The impeller can hit the case when the bearing starts to go.

 

[JennaBear]

Look into a bigger cooler. I ran a B&M on my 04.

 

[01ssreda4]

230 isn't overheating. As a matter of fact, with stock cooling, and having 95 degree outside temps I would EXPECT it to run 220+ the entire time. Remember, most of the time low speed fans don't even turn on until high teens or low twenties in temp in a stock vehicle. Add in AC blowing and towing and you get the picture....

 

[Rivieraracing]

Not sure how heavy that tractor and trailer combo are or the pontoon boat but I wouldn't really see that much of an increase in temp when I towed most things but only when I was towing my old toy hauler trailer and that wasn't anything light at all! When I had my mechanical fans it was completely that way but when I switches to electric fans out of an '06 (highly recommend that mod to you Travis) it would tend to warm up a bit more but would get knocked down quicker when the fans kicked on!

 

[FlyboyTR]

Thanks for the generous replies and suggestions. I am not loosing any coolant...the weep hole is dry. I have been hearing the fan engage...but it does not appear to hold that status very long.

What is the recommended chemical for flushing this system? I guess I also need to find a brief tutorial on the best way to do it.

 

[Rivieraracing]

I just undo a few radiator hoses and spray water through everything for quite a bit after I drain the whole system. If thats the least you are going to do, at least change out the thermostat because who knows how old it may be!

 

[FlyboyTR]

I just undo a few radiator hoses and spray water through everything for quite a bit after I drain the whole system. If thats the least you are going to do, at least change out the thermostat because who knows how old it may be!

I was rereading the different posts and while, for some, my worrisome temps seem ok to some. OK...so 220-230 is OK...but the erratic manner in which it gets there and decreased from there is of concern. My pontoon boat only weighs about 2,000 lbs, at most...although it is like towing a billboard turned sideways! My fuel mileage drops into the <9 MPG while towing...even at the slower speeds of 50-55.

I am considering just doing the full boat: radiator flush, pump, thermostat and fan clutch. Only looking at $180 worth of parts; including the Dex Cool. I think this may be the safer route and I will have the comfort of knowing exactly what is there.

In regards to the factory gauge making occasional instant jumps in indicated temp. Could this be the sender causing this?

Again...my thanks for all the input and suggestions...appreciated!

 

[FlyboyTR]

Update

Update on progress. I had a difficult time draining the radiator. I removed the radiator/overflow cap and the drain petcock and started the process. It drained very slow with some nasty looking fluid. I was only able to get about 1.5 gallons out. In the meantime I removed the intake tube and shroud cover. I had to remove the lower radiator hose from the thermostat housing to get to another gallon or so. Pulled the belts (the rear A/C belt was well past due!, fan clutch and water pump. Inspection revealed nothing remarkable. Using the garden hose I flushed out the radiator (backflushed the petcock drain and tubing, overflow tank and lines, engine block and heater lines. Cleaned everything up and installed all new components; pump, thermostat, belts, fan clutch. Refilled the system with hose water and Peak Radiator Flush. It took basically 4 gallons of water after burping and a short drive. After that I took it for a two mile ride through the neighborhood. The dash needle stayed just below one click from the mid point on the gauge. I don't remember it ever running below the mid-point. No water needed after that short ride.

Tomorrow I will drain/refill the system a couple of times, then drain all lines and refill with Dex-Cool and distilled water. If I have missed anything, please let me know!

Tonight we will go out for dinner and it will get about a 25 mile drive, including interstate. So...I am hoping it continues to operate cooler than it was. However...the proof will be when I hook up the pontoon boat and drag it down the highway. I will update later.