Cooling Question

[Bald Eagle]

Yesterday afternoon it was 100 degrees outside, so I took the truck for a 40-mile round-trip drive.  The first 20 miles (down elevation) I drove without air and the engine temp. stayed at 210 or less and the trans. temp. around 150.  The return 20 miles (up elevation I turned the air on and the engine temp. climbed to 217 and the trans temp 180.

This afternoon, I did the tow test up the 3-mile, 800-foot elevation climb with my Teardrop trailer (1200 lbs.).  As I neared the summit engine temp. was 224 and the trans. temp. was 220.  Both the engine and trans. fans were on the entire time.  The outside air temp. was 90 degrees.  Elevation change was from 7200' to 8,000'.

As I wrote in my initial post, all the cooling components are new.  The transmission has a new filter and fluid, and the cooler is the Derale #13740 with two cooling fans rated at 650 cfm.  It is mounted below the radiator.

My conclusion is as follows.  The AW4 transmission is the weak link.  Normal everyday driving it does fine, and the temp never goes over 150 degrees.  Once you add hills, slow trail driving or towing it does not like it.  I have tried three trans. coolers:  The stock cooler, a TrueCool and the Derale.  The AW4 puts out a lot of heat and works the engine harder.

My 1992 Jeep Cherokee has the AX15 manual transmission, and I have not experienced the same issues. 

[AZJeff]

You are quoting some very specific temperatures for the coolant, far more precise than the factory gauges can display.

 

What is your measurement tool to arrive at these values?

[Andy in Pa]

I think you are correct.  I had a very similar problem years ago with my 96 XJ.  Had cooling issues that I could not diagnose, (on an XJ with 45kmiles), and it turned out to be excessive heat coming from the trans due to damage to the TC input nose being egged out after an ugly bell-housing breakage (long story, it came out in 5 pieces).  After replacing the bell-housing and getting it back on the road, it took about 6 months for it to finally kill the gasket at the TC nose, and completely drain my aw-4 of all tranny fluid in about 28 seconds or less.  That was a bad day... When I pulled the trans and the TC, the nose had gotten so hot that it was "blued".

At the time I was using an additional large cooler, and the trans lines were still using the factory radiator cooler too.  I also had the electric fan on a switch and it was running.  And BTW, the fluid NEVER looked burnt or blackened or anything.  It came pouring out of my trans a bright, clean looking cherry red.

 

Clearly this is an extreme circumstance, but the point is you are on the right track.  Even traffic accidents could cause unseen damage that rears its ugly head in strange ways years later.  Turns out my bell-housing was cracked for a LONG time prior to the breakage, likely because of an accident.

[BizarroStormy]

I wouldn't trust temperature reading from a temp gun. They have to be calibrated for the material they are reading and shiny metal pieces like a water neck or radiator will always give you bad readings. Maybe you can attach a temp probe to the bottom of your pressure bottle. If you have the aluminum one from mac's that would be a very accurate reading. 

[Bald Eagle]

To answer everyone's comments, I did test the temperature at the thermostat housing and at the gauge sensor at the rear of the block with a temp gun.  The temp at the gauge sensor was within +/- 5 degrees.  The temp. at the thermostat was about 10 degrees lower.  I agree that the gauge can be off.  With regard to the transmission temp. gauge, I am assuming that it is fairly accurate.  It is reading the temp. as it comes out of the transmission.  At this point, I am more concerned about the transmission since it has little tolerance outside of any normal driving.  

After towing my 1200 lb. teardrop camper around Colorado, the bottom line is the Comanche could use more power and a much better transmission.

[Bald Eagle]

I have installed a PML deep transmission pan for the AW4.  It takes an extra quart of fluid and comes with a sensor port.  I moved the existing temp sensor from the outbound line to the pan.  Driving the same test road in my previous posts, the temperature never went above 170 degrees.  The tow test is next.  Also, removing the trans cooler from in front of the radiator/condenser has resulted in the engine temp staying at 210 or less.

My next project is to install the Thor cowl intake.  This will get the air filter in cooler air (out of the engine bay) and free up some room for a possible second battery and either an Axbeam or Voswitch box.