Seeking help on temperature.

Gidday from Oz. I have a 1997 Cherokee Sport and have been noticing some temperature variations that are causing me concern. My dealer tells me the Jeep runs at high temp but I am a bit sceptical. Normallly the temp gauge remains slightly over the first mark. But, this happens: Following a drive for a time and then entering traffic and encountering traffic lights, the temp quickly rises to the 100 mark and remains there. I feel that the auto transmission is getting hot and thereby raising the radiator temp but have installed a transcooler to no effect. The car has a new radiator, new thermostat and is not using coolant. Is anybody else experiencing this, is it normal. Any advice/help appreciated. cheers.

Billl Power said:

Gidday from Oz. I have a 1997 Cherokee Sport and have been noticing some temperature variations that are causing me concern. My dealer tells me the Jeep runs at high temp but I am a bit sceptical. Normallly the temp gauge remains slightly over the first mark. But, this happens: Following a drive for a time and then entering traffic and encountering traffic lights, the temp quickly rises to the 100 mark and remains there. I feel that the auto transmission is getting hot and thereby raising the radiator temp but have installed a transcooler to no effect. The car has a new radiator, new thermostat and is not using coolant. Is anybody else experiencing this, is it normal. Any advice/help appreciated. cheers.

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Are we talking Celsius or Fahrenheit? Because if it's 100C (which is about 210F), then your temp is just about right. IIRC my 97 (and before that my 98) all ran more or less in that temperature range. The 4.0 likes that temp and getting it to run cooler would hurt performance/fuel economy. Btw, my jeep runs 210~220F whether it's in the desert or up in mountains in the snow (after warming up that is).

Sounds about right to me - the AMC242 has a design operating temperature of 215*F (101-102*C.) If everything's in workin' order, you should see 100-ish *C after it's been running for a few minutes.

If you have an automatic, it would make sense to divorce the transmission cooling circuit from the engine coolant - just to lower the thermal load on the system (that's an accounting decision, not an engineering decision. Trust a beancounter...)

However, it sounds as though you're ticking along just fine - the only rig that I've got that runs lower than that is my 88/4.0/NP231/BA-10/D30/D35/3.07, which I've made a few mods to. I'm working on a writeup for the FAQ section - don't know when it will be done at the moment, but it's in the works. It's the "hows and whys" of the cooling system, and a few things you can do to make it work better.

5-90

Not trusting the gage calibration too much.. the symptom of temp rising a bit in traffic sounds like your mechanical fan clutch not working properly. Do you hear the electric fan kick on? The electric comes on at 5 degree or so over temp, that normally only happens in very hot weather.

Come to think of it, if you can - get a "non-contact" thermometer, and recheck the system temperature that way.

Scan the radiator - you should note a decrease going from passenger side (the side where the upper hose is connected) to the driver's side (where the lower hose goes) - assuming LHD. Yours might be reversed, if yours is RHD - that's why I mentioned where the hoses go.

The upper hose is coolant entering the radiator after being heated by the engine, and the lower hose is "cooled" coolant being picked up by the pump.

This will do two things - 1) it will tell you what sort of temperatures you're running, really, and 2) it will help to verify and quantify radiator operation...

5-90

Mine runs about 100*F to 180*F when I really work the engine, I've got a 3-core radiator which I thought was the culprit so now I'm assuming it's the thermostat.

BTW-If Bill Power is from the Adelaide I'm thinking of it's in Austrailia...

Zoro said:

BTW-If Bill Power is from the Adelaide I'm thinking of it's in Austrailia...

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well... for me the following was the giveaway:

Bill Power said:

Gidday from Oz

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Kejtar said:

well... for me the following was the giveaway:

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Musta somehow missed that...

Thanks people. This has been a great help. I will get the temp checked but your advice runs pretty much the same as the dealer advice here.
Here is Adelaide, Australia. Gateway to the Oz Outback where we can really give these vehicles their heads. Gets bloody hot so you can see why I have some concerns. Hooroo for now.

G'day!

If you're not going to be sitting still (doesn't happen much in the Outback, as I'm inclined to recall...) then the cooling system will get plenty of ram air and should be working fine.

I only note a problem with temperature when I'm going to Sacramento, in summer, and sitting in traffic.

I'd have to go thru the FSM/wiring diagrams to tell you how to do it, but there should be a way to "manually" trip the fan relay and install an override switch (easier on earlier rigs) to run the thing all the time - you can turn it on when you anticipate sitting or running slow, and increase airflow over the radiator that way. I find it helps.

Also, if you find a RedLine product down there called "Water Wetter," I heartily recommend it! I've found it to be worth a good 5*F decrease in op-temp when sitting in traffic, so it should help with your concerns as well. I don't know if it will be available to you, but it's all over up here...

5-90

Billl Power said:

Gets bloody hot so you can see why I have some concerns. Hooroo for now.

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LOL, I think I can get your heat beat In July I went wheeling in the desert in 44C weather