Overheating issues

[mike5]

Quick question: how did you run wires from the engine compartment through the firewall into the interior?

 

[tyty13]

The timing on this thread is perfect. I can add some light to these two questions. So a couple of months ago, I went Coyote Flats in the Eastern Sierras. We ended up around 10,000 feet. When we went the weather was cold (probably around 50 during the day and down to 25 at night). While on a slow/long/steep ascend my coolant temp started rising and my AT light came on. So I pulled over and gave the car a break. Later on while stationary after some slow 4low stuff, again it started climbing.

I had serviced the cooling system so I was a bit surprised. It never happened to me on the streets. But something I'd notice occasionally was stains on the expansion tank...meaning some fluid and over flowed. After my trip, I had the mechanic go through the cooling system. The issue was the thermostat. It was "sticking." But they only figured this out by removing it and testing in hot water. After changing it, I went on another trip with a lot of climbing in 85+ weather. No a single cooling issue. In my case I knew the radiator was good, it had been flushed, cracked fan replaced and coolant drained. So not hard to figure that one out.

With respect to the AT light, my educated guess is this: at higher elevation while off roading and very slow speeds, if you leave the car in drive it will usually use a higher gear than it should. This results in more torque converter slippage (by design) which generates heat. Instead if you deliberately use 1st and 2nd gear, then slippage is eliminated which reduces heat. On trips where I've done this, I had zero issues.

You can ADD a 2nd AT cooler

 

[mike5]

Sure thing there. I'd rather add a fan to the cooler than place a second one.

 

[m3at333hp]

I'd send a sample of the oil off for analysis just to be 110% sure it's not harming your transmission. But that said, it's likely due to the hot temps and reduced airflow at slow speeds. Have you done the AC fan mod to allow you to turn it on w/out running the AC so it allows you to better cool your fluids?

No, I will look around for that mod. I might also find a bigger A/T cooler. Both times this happened, I was at Cleghorn and the temps outside were not that high.

 

[m3at333hp]

With respect to the AT light, my educated guess is this: at higher elevation while off roading and very slow speeds, if you leave the car in drive it will usually use a higher gear than it should. This results in more torque converter slippage (by design) which generates heat. Instead if you deliberately use 1st and 2nd gear, then slippage is eliminated which reduces heat. On trips where I've done this, I had zero issues.

Mike, I will try putting it in a lower gear next time. Thanks!

 

[mike5]

I've seen the same tranny temp issues happen on 2011 and 2012 Jeeps. They had it either in 4H or 4L and set to Drive. As soon as they switched to 4L and used 1st and 2nd as necessary...all was well.

Let me know if you head out for some wheelin' again. I love the Sierras and might be able to make it.

 

[kuroi]

Go with electric fans and ditch the mechanical one as mechanical fans don't move much air when your rpm's are low. Electric fans will free up a small bit of HP and are not engine speed dependent like a mechanical fan is so even at low speed and rpm you get maximum air movement through the radiator which will pull more heat out of the system and keep your temps lower. Also run a higher ratio of water to anti-freeze as water is better at heat management than AF and use a product like redline water wetter. Upgrade your trans cooler as well, the stock one is too small imho.