TJ Normal Operating Temp

[Bond--007]

Hi guys. Trying to find out what the normal operating temp is for the '97 TJ. During the winter, the temp needle would stay on the 210 mark or a tough below. The last several days running the interstate to work, I noticed the temp would stay on the 0. Is this normal or is the temp running high to cause concern?

[JPNinPA]

Your temp gage gets its input from the sending unit on top of the thermostat housing. Check the wiring and the resistance between the terminals of the sending unit. It should change as temp increases. I'll post back the value chart for the unit as soon as I find it. If this reads ok it is something else. If not change the sending unit.


The only concern is your fuel air ratio will be off. Too hot is a bigger issue.

[Bond--007]

The only concern is your fuel air ratio will be off. Too hot is a bigger issue.

When running the interstate, it stays steady on the 0 like the picture. Once I get off the interstate, it comes down to the 210 hash by the time I get home (~10 miles). I was thinking it may have to do with my radiator. Most of the cooling fins are rusted out/missing from the top to about 4 inches down (on the plan to change out next weekend at the wrenching party).

[JPNinPA]

I misunderstood. I took zero as no reading. Ok scratch what I stated earlier. By chance on the highway what RPMs are you at? This may be atypical.
First thing to look at is the radiator and anything restricting or blocking air flow. Debris on or behind the radiator. Items in front of the radiator like winch or grill blackouts or spacers...
After this inspect the belt tension. Slipping belt will slow the pump.
Check the clutch fan. When cold spin the fan it should not spin more than 5 times. And it should spin. A stuck in gaged fan will cause more load on the engine.
Lastly a failing water pump where the fins are warn will not move enough fluid as quickly asa it should.


When and if you change the radiator use O because others do not have the fin density for cooling efficiently as stock.

[Bond--007]

I misunderstood. I took zero as no reading. Ok scratch what I stated earlier. By chance on the highway what RPMs are you at? This may be atypical.
First thing to look at is the radiator and anything restricting or blocking air flow. Debris on or behind the radiator. Items in front of the radiator like winch or grill blackouts or spacers...

On the highway I usually push around 3200-3500 RPMs (changing between 4th and 5th gear). Nothing in front of the radiator at all. The only issue is the cooling fins are missing or rusted out from the top to about 4 inches down in all channels (some worse than others).

I was figuring the issue was due to the radiator fins missing, but also wanted to make sure I couldn't damage the engine as long as it didn't climb higher on the temp guage

[Bounty__Hunter]

Normal, and not a temp to worry about.

[Bond--007]

Normal, and not a temp to worry about.

The magical words I was hoping to hear. Thx JPNinPA and Bounty_Hunter for the input

[JPNinPA]

On the highway I usually push around 3200-3500 RPMs (changing between 4th and 5th gear). Nothing in front of the radiator at all. The only issue is the cooling fins are missing or rusted out from the top to about 4 inches down in all channels (some worse than others). I was figuring the issue was due to the radiator fins missing, but also wanted to make sure I couldn't damage the engine as long as it didn't climb higher on the temp guage

Running at 3200-3500 rpm is up there generating a lot of heat.


While I agree with BH it is still the cool part of the year. You may. Want to keep an eye on it.

It likely is the missing top rows. I forgot to mention there are other possible causes. Thermo that didn't open all the way or something restricting flow like if you used RTV Or if the gasket moved.

[Bounty__Hunter]

Running at 3200-3500 rpm is up there generating a lot of heat.

That's the happy spot for the 2.5L

[JPNinPA]

That's the happy spot for the 2.5L

Your right, I was thinking 4.0 not the 4banger. Thanks for the correction.

[Bounty__Hunter]

Ya I had to go back and look because that caught my eye too, thinking it might be the 4.0L. Even worse if an auto.

[Bond--007]

Got the new radiator installed. Ran it for the first time down the interstate this morning. The temp needle stayed between the 2 and 1 just in front of the 210 hash mark....needless to say, the old radiator must have been making it run hot

[JPNinPA]

Great that needle is in the optimal location. You will be happier in the long run.

[Big had]

My 05 tj 4.0 runs exactly the same spot in 50 degree weather or 110 degree weather. It is an auto trans as well.
i put gauges on my trans for sending line and for pan. Also installed an external cooler, what a difference for the trans temp btw. Best thing I ever did.

[Bond--007]

My 05 tj 4.0 runs exactly the same spot in 50 degree weather or 110 degree weather. It is an auto trans as well.
i put gauges on my trans for sending line and for pan. Also installed an external cooler, what a difference for the trans temp btw. Best thing I ever did.

Mine is a manual transmission