2017 gmc 1500 5.3L 4x4 engine temp fluctuating

[Tim-1]

Has anyone been able to figure out their truck temperature fluctuating? my 2017 GMC 5.3 will climb up slightly without towing in mountain or steep pass when towing it will get as hot as three-quarter mark. Also, my truck will start going into some kind of lint mode or something. GMC checked it out and said they were unable to duplicate the problem and that the cooling system was working as designed find it hard to believe.

[mikeyk101]

When towing, how fast were you driving? I know when towing my toy hauler up serious grades, I need to drop it down a gear and drive a bit slower or mine will heat up quickly. First experience I had was going along at 55mph up a 7-8% grade for several miles (Big Horn Mtns on Hwy 16 in Wyoming) trying to keep up with another couple I was traveling with. My coolant, oil temp, and trans temp all went way past what they should have. I also got the warning about limp mode along with AC shutting off and to pull over to let engine idle. I finally found a place to pull over, let the motor idle for a bit and all the temps finally dropped back down. I found that I need to drop a gear or 2 using manual option and keep my speed down a bit. I put on my flashers and just move along in the right hand lane.

 

I also have a lower temp coolant thermostat now (194⁰ instead of the stock 207⁰) as well as the 154⁰ (70c) transmission valve instead of the stock 194⁰ one but haven't gotten a chance to tow my toy hauler up any serious grades since doing it. We have hills in Wisconsin, just not mountains, LOL!

Edited August 1, 2024 by mikeyk101

[GMh8tr72]

I am having the same issue and have not found a solution. Mechanic couldn't duplicate even though the engine run 1 to 2 marks past 210 with normal driving. Changed: water pump, thermostat, radiator based on internet searches and still overheats.  AC is ice cold.

Does anyone know if the dual radiator fans should run at different speeds as the truck exceeds 210 degree? Mine are staying at a low speed

[Tim-1]

On 7/31/2024 at 7:44 PM, mikeyk101 said:

When towing, how fast were you driving? I know when towing my toy hauler up serious grades, I need to drop it down a gear and drive a bit slower or mine will heat up quickly. First experience I had was going along at 55mph up a 7-8% grade for several miles (Big Horn Mtns on Hwy 16 in Wyoming) trying to keep up with another couple I was traveling with. My coolant, oil temp, and trans temp all went way past what they should have. I also got the warning about limp mode along with AC shutting off and to pull over to let engine idle. I finally found a place to pull over, let the motor idle for a bit and all the temps finally dropped back down. I found that I need to drop a gear or 2 using manual option and keep my speed down a bit. I put on my flashers and just move along in the right hand lane.

 

I also have a lower temp coolant thermostat now (194⁰ instead of the stock 207⁰) as well as the 154⁰ (70c) transmission valve instead of the stock 194⁰ one but haven't gotten a chance to tow my toy hauler up any serious grades since doing it. We have hills in Wisconsin, just not mountains, LOL!

Not fast at all. I had it in M1 or 2 and slinging about 25mph trying to keep rpm up. I’m going to try upload a video.

[Tim-1]

On 8/6/2024 at 12:01 PM, GMh8tr72 said:

I am having the same issue and have not found a solution. Mechanic couldn't duplicate even though the engine run 1 to 2 marks past 210 with normal driving. Changed: water pump, thermostat, radiator based on internet searches and still overheats.  AC is ice cold.

Does anyone know if the dual radiator fans should run at different speeds as the truck exceeds 210 degree? Mine are staying at a low speed

 

Just now, Tim-1 said:

Not fast at all. I had it in M1 or 2 and slinging about 25mph trying to keep rpm up. I’m going to try upload a video.

I just did the same repair but havnt tested them yet.