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Remote Trans cooler Strange temp readings

WebDog

NAXJA Forum User
Location
Center City, MN
I decided to move my trans cooler to a remote location and have a dedicated cooling fan on it.

I mounted it on the hood with about 1 .5" of clearance from the back and the fan on the bottom on pull mode.

With a IR temp gun the input is 190* and out is 140* after doing a long uphill freeway section.

But this is where it gets strange, the trans temp gauge I installed reads about 230 - 260*. When I measure the probe location in the hose it is 190*.
I thought it was a bad gauge so swapped it out for a more expensive better one. and the same results.

I tested the IR gun on my radiator and it is reading exactly what my dash and digital gauges are reading so I trust it.

So why would I be seeing such a difference in temperatures from the two temps?
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Since the IR gun is reading surface temp is it possible that your not getting good heat transfer out of the fluid to the cooler? When you are taking the reading are you leaving the engine run so that the trans is still pumping fluid? Is it possible that the cooler is getting an air pocket when you open the hood making the line temps drop?

I agree it doesn't make sense that the Rad temp readings are correct but that the trans is not with the IR gun.
 
I dont know if it did have a air pocket that it would drip 50* in the 3 seconds it takes to pop the hood and measure it. The T that holds the probe is steel and would not cool that fast ether and it reads the same as the cooler input.

I have the engine running when testing.

I am installing a new radiator since mine is clogged up a bit and will put the cooler back infront of the radiator to test the temps then.

The engine is running 5 - 10* cooler without it infront of the radiator.
 
Well since the sender fitting location and the cooler input read the same I'd think its the gauge setup even thought you've tried 2 different ones. Is the gauge a mechanical one or an electric one? If its mechanical is it possible that its picking up heat from something else thru the pickup tube? If its electric did you use the same sending unit for both gauges or change the entire gauge setups?
 
Is the T fitting that the probe is mounted to grounded? If its just a T fitting spliced into the rubber hose you will need to ground the fitting to get the proper reading for the guage. I would also try and find a place for the cooler out of the engine bay. You are basicaly sucking hot engine air into the cooler.
 
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I put it back infront of the radiator to do a test drive tonight. Tomorrow my new radiator comes so I wanted to get a base line temp before it goes in.

The probe was grounded.

Quinn on facebook said something about mounting it under the jeep. It is not a bad idea, and I could make a steel cage to protect it from rocks, etc...
 
Max, were you reading the hose or the connection at the cooler itself? The hoses will insulate as we found when looking at coolant temps during the electric water pump installation. We also discovered that the IR thermometer does not like shiny surfaces. In all of the above cases, the readings were low... By a chunk...

The TJ guys have transcooler kits available to them that mounts the cooler under the rig to the frame rails. Only problem I can see is the lack of real estate. I am thinking of using the stock front skid plate as a mounting point for a fan assisted transmission cooler. It is wide enough to get both a trans and an engine oil cooler inside. My intent is to space it down a couple of inches to make room for the sway bar. If I ever go to an antirock, there would be no reason to space it down.

What do you think? I mean, what good is the stock skid in a lifted Heep? Well, it does make a good spot to mount a holder for the quick disconnects...

Weird about the shiny surfaces...
 
I was reading on the cooler itself.

I have tried a bunch of new things since the thread.

I put in a new aluminum radiator 3 core as i bought it before I realized it was the trans causing the engine to heat up. I put the cooler probe in the transmission pan and put the cooler infront of the radiator. it was causing the jeep to run hot and the trans would shoot to 260+ after a long highway drive.

I then moved the cooler above the rear axle with a dedicated fan, the engine ran around 180- 190 so big drop in temps and the trans still creeps to 260+ this is after about 60 miles of driving.

Strange thing is it does not have any physical differences when hot still drives the same. And I can only assume I have been toasting the trans the last 30,000 miles I have thought my engine was having heat issues.

So What is the best step to find the cause of it minus pulling the trans out and tearing into it? This is my daily so whatever I do I need to be able to do it over a weekend.
 
ya check for torgue converter lock up first. I know when I run in manual mode without the TC on, the tranny heats up pretty fast when street driving.
 
Yea I dont think it is locking up, my white 88 I could remember when tapping the brakes the RPM goes up a little. This jeep wont do that.

So whats the best method to fix it, the solenoids I tested OHMs recently and where all in spec.
 
So whats the best method to fix it, the solenoids I tested OHMs recently and were all in spec.

Crap, there goes my next suggestion. I've heard that some(any electrical really) parts test good but are really bad, or on the fringe end of the range and act bad. So maybe switch solenoids if you have access to a "good" one?
 
ok so I think I fixed it... The white brake pedal switch was not even close to touching the pedal...

I have lockup now and on a 15 mile freeway drive it only has gotten to about 180ish


I need to adjust it some more but I think I might be ok, I plan to drain the pan and refill a few more times to swap the rest of the fluid.
 
Awsome, good find
 
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