Overheating towing with Denali 6.2L - Losing my F'n mind!!

[Bucky1]

Man there are some real plausable explanations throughout this thread.
I am wondering about the oil pressure issue. Seems like a likely possiblility. Towing can elevate oil temp, which can also lower viscosity and pressure. Roll out of the throttle and come to a stop at lower rpm, and the oil pressure further drops, to a point where maybe a sensor issues or the lifters maybe won't pump up? If it were cutting because it sensed low oil pressure, there should be a code. Plus, I don't think it will cut the engine with low oil pressure. I had a bad sensor, and it would show 0 on the gauge and not kill it. But it did show a code.
One other thing that can further lower oil pressure is lower crankcase pressure....which could happen at higher altitudes, as the crankcase is not entirely sealed. On our race engines, as soon as we throw a vacuum pump on them, the oil pressure drops a bit.
But, I would think you would hear the lifters rattle as long as the radio was off and the blower not overly high.
Just a thought.
Maybe if this is it, a bit higher viscosity oil could get you by when towing?
I might be way out in left field though. It happens.

 

[puckhead]

Man there are some real plausable explanations throughout this thread.
I am wondering about the oil pressure issue. Seems like a likely possiblility. Towing can elevate oil temp, which can also lower viscosity and pressure. Roll out of the throttle and come to a stop at lower rpm, and the oil pressure further drops, to a point where maybe a sensor issues or the lifters maybe won't pump up? If it were cutting because it sensed low oil pressure, there should be a code. Plus, I don't think it will cut the engine with low oil pressure. I had a bad sensor, and it would show 0 on the gauge and not kill it. But it did show a code.
One other thing that can further lower oil pressure is lower crankcase pressure....which could happen at higher altitudes, as the crankcase is not entirely sealed. On our race engines, as soon as we throw a vacuum pump on them, the oil pressure drops a bit.
But, I would think you would hear the lifters rattle as long as the radio was off and the blower not overly high.
Just a thought.
Maybe if this is it, a bit higher viscosity oil could get you by when towing?
I might be way out in left field though. It happens.

I do noticed a very slight rattle (if you can call it that) when I first get is started up after overheating. Don't know how else to describe it really, just a rough start. I run 5W30 now, how high should I bump it up to? I am in a colder climate.

I will be wrapping my fuel rails soon, have most of the fuel lines done right now. Waiting on funds for a new radiator(planning on the new expensive Mishimoto) and water pump although both seem to be operating just fine.

I will also try the bubble test for the head gasket.

 

[kbuskill]

I do noticed a very slight rattle (if you can call it that) when I first get is started up after overheating. Don't know how else to describe it really, just a rough start. I run 5W30 now, how high should I bump it up to? I am in a colder climate.

I will be wrapping my fuel rails soon, have most of the fuel lines done right now. Waiting on funds for a new radiator(planning on the new expensive Mishimoto) and water pump although both seem to be operating just fine.

I will also try the bubble test for the head gasket.

I'd really like to see if just wrapping the fuel rails/lines does the trick.

The only problem with changing so many things at once is you don't know what actually fixed it.... to many variables.

 

[puckhead]

I'd really like to see if just wrapping the fuel rails/lines does the trick.

The only problem with changing so many things at once is you don't know what actually fixed it.... to many variables.

I will be doing the wrap first, I will try and take it out and see if I can replicate the issue after that. I have seen people replace all the other stuff and not fix it so I hope this will do the trick. Time is limited right now, new baby to come next Friday!

 

[kbuskill]

I will be doing the wrap first, I will try and take it out and see if I can replicate the issue after that. I have seen people replace all the other stuff and not fix it so I hope this will do the trick. Time is limited right now, new baby to come next Friday!

Awesome.... I understand.... congratulations on the new addition!!!

 

[mattt]

How will you do the bubble test without a cap on the radiator?

 

[rubicon1976]

Sorry for not getting back to this for quite a while. I gave up on troubleshooting this issue with my Yukon and just decided to buy a newer Tahoe. I purchased a 2015 Z71 yesterday. Head/head gasket seems like the most plausible theory at this point but I will never know for sure. I am bummed because I loved the Yukon. I feel defeated for not figuring out the issue for sure but I just ran out of patience. I think it will still be a great truck for someone who doesn't need to tow heavy trailers into the mountains. I drove it without a trailer up to Devil's head peak last Saturday and it did fine. Thanks for all of the replies and suggestions. This is a great forum from what I have seen so far and I look forward to participating and contributing to the forum in the very near future.

 

[puckhead]

How will you do the bubble test without a cap on the radiator?

I assume just on the overflow/fill tank.

 

[swathdiver]

...buy a newer Tahoe. I purchased a 2015 Z71 yesterday.

Do post up some photos of the new one when you can!

 

[rubicon1976]

Here is my Z71

 

[puckhead]

**Update**

Alright, I wrapped my fuel lines and rails in the engine bay. Didn't do the ones under the truck next to the transmission.

Drove it today in 95-100 degree temps in the city then up a mild mountain pass. Here is what happened.

Denali did good all day in the city with the A/C on the whole time. Started heading up the hill and the temp spiked to about 200. Turned the A/C off and pulled off to the side of the road and it cooled down real quick. Even turned the A/C back on. Hooked up my OBDII reader for some more accurate reads.

Started up the hill again with A/C on and got the Service Stabiltrac/Traction Control Off messaged. Didn't notice any performance issues so I kept going and the warning light eventually went away (10 minutes maybe). During this time my temps went up to 232 degrees but it never died the rest of the trip. It cooled down for a while then spiked to 225 as we were getting home.

Don't really know what to think of these results. Is it normal/safe for the temp to get up that high? I was unloaded and not towing. Just me and the A/C.

Edit to add. Wife always fills up with 91 octane, so do I. I also dumped in a bottle of Sea Foam for good measure.

 

[gpracer1]

Not towing and that high of trans temps I wonder if the converter is not locking up.

 

[swathdiver]

During this time my temps went up...

Have you pressure tested the radiator and made sure both fans are functioning at full power?

 

[puckhead]

Have you pressure tested the radiator and made sure both fans are functioning at full power?

I thought the shop I took it to did the pressure test but that was just for the fuel pressure. How do I go about doing a pressure test? Is there a gauge I can buy for the coolant reservoir?

The fans seem good. I have seen both at a low and a high setting.

@gpracer1 These are engine temps, not tans temps. Trans is good.

 

[swathdiver]

How do I go about doing a pressure test? Is there a gauge I can buy for the coolant reservoir?

Exactly! Craftsman, Harbor Freight, Amazon, local auto parts store or maybe even a neighbor with a race car down the block.

 

[puckhead]

I will check that, thanks! This thing is killing me!

 

[kbuskill]

I will check that, thanks! This thing is killing me!

To me these are positive results.

To keep me from going back and rereading 6 pages... Did the stalling problem happen before without pulling a trailer???

 

[puckhead]

To me these are positive results.

To keep me from going back and rereading 6 pages... Did the stalling problem happen before without pulling a trailer???

Yes it did. I would say its a hair positive. I think the heat tape helped a bit.

 

[gpracer1]

I thought the shop I took it to did the pressure test but that was just for the fuel pressure. How do I go about doing a pressure test? Is there a gauge I can buy for the coolant reservoir?

The fans seem good. I have seen both at a low and a high setting.

@gpracer1 These are engine temps, not tans temps. Trans is good.

Sorry I thought I saw trans temp

 

[intheburbs]

**Update**

<snip>

During this time my temps went up to 232 degrees but it never died the rest of the trip. It cooled down for a while then spiked to 225 as we were getting home.

Don't really know what to think of these results. Is it normal/safe for the temp to get up that high? I was unloaded and not towing. Just me and the A/C.

Edit to add. Wife always fills up with 91 octane, so do I. I also dumped in a bottle of Sea Foam for good measure.

Both of my trucks stay dead-nuts at 210° 100% of the time. The needle never moves. Only time they go higher is when I'm towing, and only then when I'm really working the engine.