2007 GMC Yukon XL Denali 6.2 Overheating at a stand still

[Bocaguy]

Hi Everyone. Long time reader, first time poster!. Thanks in advance.

So I have a 2007 GMC Yukon XL Denali with a 6.2. I noticed my water pump was leaking a bit of water, not much so I decided to change it out. I also took the opportunity to change the t-stat. While I was changing these out, I noticed the radiator had rust and corrosion on it, so I changed it out as well. To complete the whole project, I changed the overflow expansion tank.

So I am in AZ and it is 50 to 80 degrees out, but it will start to get a lot warmer here shortly. The car will run at 217 and up to 228 at idle, and if I am not moving and rev it up, the temp will drop right away to 208. I am using my digital scan tool, to get these temps. I have also changed out the coolant temp sensor. I pulled the thermostat out, and it will run at a max temp of 190. I put a different, brand new thermostat in, and it is doing the exact same thing of running at 217 to 228. High speed fans kick on when the AC is turned on.

I am stumped as to why after changing all these components, it is running hot? Before changing everything, it always ran at 210 unless I was pulling my utility trailer up a hill or mountain road. Any help would be greatly appreciated.

 

[Fless]

What make and model of radiator? Does it have the proper (small) restriction in the fitting for the hose that goes to the surge tank?

If you still have the old radiator you could compare the two.

 

[Bocaguy]

I will check.

 

[Foggy]

Also, your factory coolant fans don't kick on until about 220* or so..
They come on low speed first, then will kick up to High if the temp doesn't come
down and/or the AC head pressure requires it to...
You also may still have some trapped air in the system from the repairs

Its very very weird that your old radiator would have "rust" as it is plastic and aluminum....
Maybe just the color of dried up DexCool ??? possibly
Also, what brand etc details of NEW Radiator and New Water Pump & TStat did
you use ??????

 

[rockola1971]

That "rust" is Dexcool (DEXPUKE) that has had either the green antifreeze(Ethylene Glycol) mixed with it (Which is a no no) or alot of air or it has just broken down. This is why I wont use it. I had a similar problem years ago on a Camaro with 2.8L V6 when I installed a reman longblock and all new stuff you typically would put on a longblock (Water Pump, Wires, Spark Plugs, etc.) It was the weirdest situation that really got me thinking and I found it. It turned out A1 Cardone which was one of the rebuilders that provided rebuilt water pumps for autozone (where I got all my parts for this motor install) had put the wrong impeller on the water pump. The impeller blades showed that the coolant did NOT get pumped the correct direction when you paid attention to the serpentine belt direction of rotation on the water pump pulley. All it did was cavitate the coolant. I got with the manager and alot of workers were very interested and we pulled out the manual for the Camaro and looked at crank rotation, serpentine belt direction and water pump impeller blade direction and after all that was discussed and proven it proved that the wrong impeller was on the water pump. All of their stock had the wrong impeller. I dont believe they had any new water pumps at the time so we couldnt use that to compare with. Manager called A1 Cardone and we threw our evidence on the table and sure enough they screwed up. A1 cardone sent me a replacement with the correct water pump impeller installed and no more overheating. I wonder to this day how many people got screwed, lost an engine due to overheating, blew a head gasket, etc during that period. This was more than likely a problem across the U.S. This happened in 1997/8 when I was stationed in Northern FLorida.
That car would just run the temp gauge to the red until you shut it down while idling. Driving it just made it peg faster. Ran fine after the proper water pump was installed.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

I cannot personally help you with your question; however, I am very interested in the solution to your issue, as we have the same truck.

 

[donjetman]

What brand, temp rating, and thermostat pt# did you install?

 

[Skibum]

Hi Everyone. Long time reader, first time poster!. Thanks in advance.

So I have a 2007 GMC Yukon XL Denali with a 6.2. I noticed my water pump was leaking a bit of water, not much so I decided to change it out. I also took the opportunity to change the t-stat. While I was changing these out, I noticed the radiator had rust and corrosion on it, so I changed it out as well. To complete the whole project, I changed the overflow expansion tank.

So I am in AZ and it is 50 to 80 degrees out, but it will start to get a lot warmer here shortly. The car will run at 217 and up to 228 at idle, and if I am not moving and rev it up, the temp will drop right away to 208. I am using my digital scan tool, to get these temps. I have also changed out the coolant temp sensor. I pulled the thermostat out, and it will run at a max temp of 190. I put a different, brand new thermostat in, and it is doing the exact same thing of running at 217 to 228. High speed fans kick on when the AC is turned on.

I am stumped as to why after changing all these components, it is running hot? Before changing everything, it always ran at 210 unless I was pulling my utility trailer up a hill or mountain road. Any help would be greatly appreciated.

I had the same problem with my 2007 (240k) Denali. Replace everything, had to replace the thermostat again. Check for any small leaks with your head gaskets.

 

[swathdiver]

Guess @Bocaguy is still on the beach!

 

[Snowbound]

Sounds like air in the system or steam lines are plugged up with that crud. Take that small hose off that comes off the heads and run it to the overflow and cap the radiator fitting and see if you have coolant coming through that hose while it’s running. Might have to vacuum bleed it if that hose isn’t plugged. Might be a good idea to run some flush through it to make sure it’s all cleaned out.
If you’re not using premix coolant make sure you use the correct water and not tap water. Most people believe distilled water is what should be used but actually it’s not. The process in distilled water is to boil off the water which leaves behind the calcium and magnesium and then condense the vapors back to a liquid. The problem is the process leaves the water ionically unbalanced. That water will strip electrons from the internal parts of the engine and do damage over time. The only water you should use is softened water. That does not mean you’ll have salt in your engine. The process uses NaCl and as the calcium and magnesium is removed it is replaced with sodium ion making the water ionically stable.

 

[THarber]

That's pretty close to where it needs to be (+-210). Changing the thermostat will do no good unless you program the computer to turn the fans on sooner. That can be accomplished via HP Tuners or other paid programs. Make sure however, that you have purged all the air out of the system. These trucks are notorious for getting air locked. The easiest way to do so is to loosen the upper radiator hose at the block and let any air out or use a pressurized system to refill coolant.

 

[gooffeyguy]

I know normal temp is about 210, but mine always runs at 197/198 and sometimes while idling in the summer will go up to 205. This is viewing the temp with the Torque Pro app or on the DIC using the AutoSync add on. I don't think I've ever had it get to 210, even in summer, full of people, driving through the Smokey Mountains

 

[Sangster]

I've been having this same issue with my 2013 Denali. Replaced the radiator with an all aluminum when the stock radiator plastic ends cracked. Still kept getting warm. Replaced water pump with new OEM pump. Replaced thermostat with OEM. Replaced any sketchy hoses. 7/9 blade e-fans. I have no leaks, and expansion tank is full. Using Torque Pro app, at idle with AC off, temp will creep up to 225 and then the fan will kick up to high. Temp will drop down to 215 and the fan will kick down to low. Temp will then creep back up to 225....fan goes back to high....temp goes down to 215.....rinse and repeat. With AC on, fan kicks to high almost right away and stays on. Temp depends on if I'm in stop and go (gets warm) or highway (stays 200-210). I also have a Trucool 40k trans cooler mounted in front of the AC condensor/radiator.

I'm wondering if the trans cooler (trans will go up to 170ish when the engine coolant is up at 220+ but generally stays in the 150-160 range) is blocking air flow through the AC condensor/radiator enough to cause it to run warm?

What temp SHOULD the fans kick to High at? I'm Blackbear tuned and Justin says it's programmed to kick to HIGH fan "10-15 degrees cooler than stock", but I'm not buying that. If that were true, then @ stock, the fan wouldn't go to high until 235 and that's way too high.

#stumped

 

[swathdiver]

I've been having this same issue with my 2013 Denali. Replaced the radiator with an all aluminum when the stock radiator plastic ends cracked. Still kept getting warm. Replaced water pump with new OEM pump. Replaced thermostat with OEM. Replaced any sketchy hoses. 7/9 blade e-fans. I have no leaks, and expansion tank is full. Using Torque Pro app, at idle with AC off, temp will creep up to 225 and then the fan will kick up to high. Temp will drop down to 215 and the fan will kick down to low. Temp will then creep back up to 225....fan goes back to high....temp goes down to 215.....rinse and repeat. With AC on, fan kicks to high almost right away and stays on. Temp depends on if I'm in stop and go (gets warm) or highway (stays 200-210). I also have a Trucool 40k trans cooler mounted in front of the AC condensor/radiator.

I'm wondering if the trans cooler (trans will go up to 170ish when the engine coolant is up at 220+ but generally stays in the 150-160 range) is blocking air flow through the AC condensor/radiator enough to cause it to run warm?

What temp SHOULD the fans kick to High at? I'm Blackbear tuned and Justin says it's programmed to kick to HIGH fan "10-15 degrees cooler than stock", but I'm not buying that. If that were true, then @ stock, the fan wouldn't go to high until 235 and that's way too high.

#stumped

What brand of radiator? Is there a restrictor in the radiator or line that goes to the expansion tank? Some radiators are missing this feature which causes temperature issues though I forget which way.

Have you tested all three relays? I have the stock transmission cooler and mine has similar temps as yours, might be something going on inside the trans? Is the converter still locking up?

Are you sure there are no air pockets in the system?

 

[Sangster]

What brand of radiator? Is there a restrictor in the radiator or line that goes to the expansion tank? Some radiators are missing this feature which causes temperature issues though I forget which way.

Have you tested all three relays? I have the stock transmission cooler and mine has similar temps as yours, might be something going on inside the trans? Is the converter still locking up?

Are you sure there are no air pockets in the system?

This radiator: https://www.amazon.com/gp/product/B01LY5ZSB4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Not sure about a restrictor, but I was having overheating issues before I replaced the radiator.

Which relays are you referring to?

My stock radiator temps were about 30-40 degrees warmer than they are now with the TruCool 40k. That seems in line with other testimonials I've seen. I'm happy with the trans temps. Converter locks up fine, what would make you think it wouldn't? I'm not experiencing transmission heat issues, even before the aftermarket cooler.

Pretty sure there aren't any air pockets, it's been a good 15k-20k miles since I swapped everything out.

 

[swathdiver]

This radiator: https://www.amazon.com/gp/product/B01LY5ZSB4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Not sure about a restrictor, but I was having overheating issues before I replaced the radiator.

Which relays are you referring to?

My stock radiator temps were about 30-40 degrees warmer than they are now with the TruCool 40k. That seems in line with other testimonials I've seen. I'm happy with the trans temps. Converter locks up fine, what would make you think it wouldn't? I'm not experiencing transmission heat issues, even before the aftermarket cooler.

Pretty sure there aren't any air pockets, it's been a good 15k-20k miles since I swapped everything out.

The fans are operated by three relays to either have them run at low speed or high speed.

I am also in Florida and my temps are about the same with the stock transmission coolers. Have you cleaned the fins on the condenser or changed grills or... Wait a sec, what are the condition of the baffles, those tar paper like pieces that go on either side of the radiator and one underneath? When these deteriorate and fall away, a lot of air then makes its way around and not through the radiator.

Here's a pic from the internet:

The one to our right is intact and in place. The one on the left has fallen out of place some. Mine were falling apart so I replaced them when we did the bumper cover.

 

[Sangster]

Both of my baffles are flimsy/torn and not doing anything. I think they both are flimsy enough to have fallen down.

But could that be enough to cause it to run too warm? The "fins" on the radiator (new) and trans cooler (new) are clean. The AC condenser looks good too.

 

[swathdiver]

Both of my baffles are flimsy/torn and not doing anything. I think they both are flimsy enough to have fallen down.

But could that be enough to cause it to run too warm? The "fins" on the radiator (new) and trans cooler (new) are clean. The AC condenser looks good too.

If they are not doing what they are supposed to do, yes, the motor will run warmer as too much air is getting around the radiator and not through it to cool.

 

[Sangster]

I'm not convinced they would help for my specific issue. I don't have any cooling issues at highway speeds, which tells me that there is plenty of airflow through the radiator. When at slow speeds and relying on the fans, the fans PULL air through the radiator from inside the fan shroud.....so those baffles aren't doing anything to help with that. The baffles are to direct air through the radiator at speeds where the fans are turned off. They don't do anything at speeds that use the fans for airflow. I don't have any cooling issues then....only at slow speeds and while stopped (idle).

 

[Fless]

Open baffles could allow engine heat (pushed by the fans) to recirc to the front of the radiator at idle or low speeds. What's to be lost by making them whole again? If nothing else it could disprove my statement above. I'd be curious.