Strange coolant temp behavior.

[GitEmSteveDave]

So I had the engine replaced end of last August and had Jeep flush and refill the coolant earlier this year. My previous engine always ran cool(would take like 5 minutes sitting at a light in traffic for it to hit 219-221 and the fan kick on), but this "new" engine seems to run hot(cooling fan kicks on when doing almost any city driving).

Lately, since the temps have been hotter, I notice the temp creep up to 219-221, the fan kick on and it drops down to ~204, rinse and repeat, but then all of a sudden the temp will drop down to 199 and stay in that area for a long time and almost act like my old engine.

Any thoughts on this?

 

[LibertyTC]

Summer temps make my eyes glued to the temp gauge/ scangauge. I've often wondered why the jeeps temps can be all over the map.
I have never tried, but have thought about removing the thermostat in summer LOL.
I just have the electrical cooling fan & I think adding the clutch fan may stabilize temps better in summer especially.
Driving conditions like stopped in traffic obviously heat things up good, and then the high speed electrical kicks on and temps drop, thankfully!
Once you are moving everything seems perfect.
Going slow especially climbing off road in 4x4 mode for an extend period is a wow heat. Hood louvers a great idea if you are summer off roading. Or just take the hood off ~!
I pulled over before and lifted the hood for a few and gave it some revs and watched the trans light go off. Added the 42RLE PML pan with drain plug solved that.
Many times when pulling the boat I wished that I had a manual override to continuous high speed fan only.
If I had it my way, I surely would have programmed in a lower temperature setting for the high speed fan to kick in.
What about a high speed impeller or performance water pump is one available?
My last thought is this radiator is awfully small. All may be cured if we could we could just mount a larger capacity aluminum rad and faster dual fans up front !
Calling Ron Davis rads, can you help with a real custom rad for my KJ??

 

[HoosierJeeper]

The mechanical fans helps a ton when you're in stop and go. It always runs and when you accelerate it sounds like a jet from the fan fully locking on.... and AC stays super cold always!

 

[renegade 04]

I would buy an all aluminum radiator and call it a day. My jeeps runs 195 all day everyday.

 

[GitEmSteveDave]

OK, a little update.

Had a high temp leak in my coolant system(If I parked her and the coolant temp was like 208 or higher, when I came back a few hours later, there would be a small puddle under her), so I brought it in to have it looked at, and while up on the lift, I spotted the leak by the thermostat housing. Made an appointment for Monday(yesterday) and had them replace the housing AND thermostat(which I suspected might be my problem if it wasn't opening at the right temps). Picked it up today($215 for the thermostat+housing plus an oil change) and drove her around for ~30 minutes, and she didn't go above 206. I could even see the temp drop after I drove for about a minute straight.

 

[JeepJeepster]

Just an FYI, the mechanical fan made no difference in the temp of my transmission but it does keep the engine at a more constant temp. The engine use to go up to ~217F and the fan would kick on and drop it to 195F. After replacing the thermostat with a new mopar unit and adding the mechanical fan+HD clutch, the engine stays between 200-204F and thats it. I guess the new mopar tstat has different specs b/c it runs ~5F hotter now.

The factory transmission cooling is a joke on the 2004 KJ. It might be better with the additional cooler in the radiator.

 

[LibertyTC]

I'm happy to hear that the mechanical fan clutch system, along with the new thermostat, is keeping the hoat cooler now.
My 04 had trans temp lights off road climbing, in 93F days. That was until I got rid of the stamped steel trans pan.
With the 1.25 quart oversized aluminum PML 42RLE pan, it cools off much quicker, & haven't had a problem since.
I wish OEM would have considered a transmission cooler, placed up front, with it's own electronically controlled fan on it as well.
If you get a Trans temp light, you have over heated the ATF+4 trans fluid, & should change it ASAP !

 

[JeepJeepster]

Ive never gotten the trans temp light but Ive seen it up to 240F in the pan, which means the fluid going to the cooler was most likely hotter. I was hauling a load of mulch and it was all she would do to just maintain 55mph. It was in the 90's and sunny that day though.