Why the overheating?

[Coast2Coast]

This winter I was ice fishing a lot and on one trip I had to go over about a foot of snow for a few miles across a lake. The temperature was about -10 and the truck started heating up to alarming levels after a couple of minutes of driving at 15mph. I had to stop and put it in low and just crawl along for a while till the temperature went down. Then stop and switch back to hi, drive normal for a few minutes till the temp gage went way up, then switch back to low again. This continued for the 20 minute trip across the lake a few times that weekend.

My truck is an auto, so I thought that I'd heard the transmission cooler was mounted inside the radiator, causing the thing to heat up. So I thought, easy, I'll just throw an external tranny cooler in there. So I opened the hood and looked for a place to mount one. Then I saw that there was already one mounted in front of the radiator. Wtf? This isn't good. The truck has high mileage, is it just too warn out to work hard?

 

[I_bRAD]

You sure that's not the AC condenser in front of the rad?

 

[Singtoe]

Sounds like the fan clutch went out.

 

[Skidmarcx]

With those ambient temps I'd look at your coolant mixture and for signs of a clogged radiator... Perhaps even a sticking thermostat

 

[Coast2Coast]

You sure that's not the AC condenser in front of the rad?

I suppose it could be, I'll have take a look underneath now that the snow finally melted where I'm at.

Can anyone direct me to an external transmission cooler that will work well with these trucks?

 

[t4r4life]

Check your fan clutch, check your radiator for blockage, check your thermostat see if it's stuck.

 

[Coast2Coast]

Yesterday I took it out on the highway and the temp on the scan gauge started creeping up to 105 degrees C. This is the first time this has happened during normal driving. I took it down a trail and went through a little mud hole and the temp went up to 110 degrees C. During normal driving it slowly drops back to about 102 degrees.

The in dash temp gage didn't move at all during any of this, but the scangage has been showing the temperature rising, mostly when I'm on the gas hard on the highway, pushing through mud or snow, or when I'm driving very slow or stopped. But the engine has never actually overheated, just indicating hotter than normal.

The fan is running, I've never seen it stopped while the truck is running. The rad is full of coolant and the res is at the top fill line. I took the rad cap off and lightly reved the engine and coolant was rising upward in the hole. The oil looks normal and coolant looks like new. I'd like to check that thermostat but I can't do that kind of work with the on street parking which is frustrating. I'm gonna go bomb it through some mud and see if I can get the factory gage to rise, to make sure the scan gage isn't just fooling me.