5.3l doesn't like towing grades with 6000 TT... Temps up!

00Silverado4x4 · April 27, 2016

Why in the world would you want him to replace the thermostat?

From what is described, it's operating as it should. There is no need to throw money away by replacing parts that are not broken.

OP was asking for suggestions and the truck being 5 years old and unknown number of miles. I treat the thermostat that same as a spark plug. Just because it's running doesn't mean it couldn't run better and from time to time parts need to be replaced. If the thermostat is starting to get gummy and not opening as quickly as it should it could lead the situation the OP was experiencing, especially when under load such as towing. Again it was only a suggestion.

Snoringbear · April 28, 2016

OP was asking for suggestions and the truck being 5 years old and unknown number of miles. I treat the thermostat that same as a spark plug. Just because it's running doesn't mean it couldn't run better and from time to time parts need to be replaced. If the thermostat is starting to get gummy and not opening as quickly as it should it could lead the situation the OP was experiencing, especially when under load such as towing. Again it was only a suggestion.

No worries 00Silverado, best to err on the side of replacing proactively instead of reactively. Actually, although I'm retired now (thus have idle time to noodle in forums such as this) prior to retiring I was an operations mgr for a large high tech company. And, my operation was heavy into Lean Manufacturing and TPM which is a critical component of LM. Anyway, the short thesis concerning TPM is that it's a method of statistically managing repair, replace parts, maintain critical equipment and machinery. A quick and simple example would be your thermo replacement. Let's say you're a fleet manger of freight trucks and your maintainence logs show empirical data that your trucks thermos are failing at around 100k miles. Then, as part of your preventative maintainence program you would routinely include thermo replacement, guard banded sufficiently to avoid failures of this part. Not rocket science, but key to keeping critical eq up and running. Anyway, replace your thermo, you'll sleep better

Jon A · April 28, 2016

The easiest improvement the OP can make without turning a wrench is a tune that turns the fans on more aggressively (first verify both fans are working, of course). The 2011's still only have the fans on 60% up to nearly 230 degrees. After that they go to 90%+ which is probably why the temp stops right there. Making the fans crank on harder starting in the 215-220 range will help both engine and transmission temps. HP Tuners is cheaper than a new radiator and will be helpful for all sorts of other things.

As for the thermostat, they do wear out--and particularly if a vehicle has ever been severely overheated before, they can be damaged. A thermostat after a severe overheat may not open fully anymore. For a part that's only $10 or so and easy to swap, I certainly don't worry about somebody wasting their money on one.

IIRC the 2011's had a pretty reasonable ~194 degree thermostat so a stock replacement would be fine and there wouldn't be a whole lot to gain from a lower temperature aftermarket one. But if you're on the edge, every little bit helps so you may want to try a 180 or so--if you start at a lower temp at the bottom of the hill, you'll probably end up at a lower temp at the top of the hill, depending upon the hill, etc. They're cheap and easy to swap so it's easy to try and see if there's an improvement.

I'd do those things before worrying about your radiator and trans cooler (assuming the stock parts are in good shape and not leaking, etc). Those parts get expensive for Genuine GM and are a lot more trouble to install.

two_wheeled · July 15, 2016

I have a 2011 with the 5.3L pulling a 25' toy hauler. I'm experiencing the same issues with heat. When climbing extended grades my trans temps would climb to 240. Engine to 236. (As measured from OBD, not the dash gauge)

I installed the largest plate-fin trans cooler I could find. It's in-line with the existing cooler. My trans temps dropped 30-40 degrees both around town and while towing.

However, my engine temps are still climbing to 230+ when towing on grades.

A neighbor suggested that a larger radiator from the 6.0L or even a diesel model might fit as a direct swap for the stock radiator that came in my 2011. Anyone heard of that?