GreyJeepy00

Within the past year I’ve replaced the entire cooling system on my XJ with quality parts, it was totally fine until coming home from work about three weeks ago, about 90+ outside doing 65 after about 20 mins, I noticed my temp rising to about 230-240, pulled off to the service road and it stayed steady at 225-230, around town the car is fine won’t go past 210 or occasionally 225 if I’m driving longer than an hour or so. I took the car upstate about a 3 hour drive, went through NYC and in heavy traffic she runs cold, second it started moving 50-65 she’s starts running hot, reading the temp through my code reader hottest it got was 243 degrees going up the parkway, blasting heat and going slow dropped it back to 225, on the way back from my trip later that same day it ran ice cold didn’t go past 210 going 70+ until the last 45 mins where it might have jumped up to 220-225, couple days ago I had to drive 4 of my friends to the train station after about 15 mins of 40-50 mph it started running hot again, so under multiple instances I’ve concluded it’s only occurring during Loaded/Long term use Around town it’s usually fine, looking for an personal insight, my xj is my daily and I take it on a 400-500 mile round trip once a month or so and would like to not have to worry about running hot without the expense of a car payment lol

List of parts replaced
CSF Rad
continental electric fan
Upper and lower rad hoses
radiator express copper brass heater core
heater hoses
overflow tank
mopar rad cap
fan clutch
water pump
185 thermostat and housing
Head and head gasket 47k miles ago
Flushed antifreeze about 6-7 times
Currently at 247k miles

exasemech

Looking at your parts list the one thing you didn't replace was the water pump. People have found that the impeller will rot away over the years.
is that your problem, who knows, but probably worth replacing

That Jeep Guy XJMJ

Mechanical fan in good order? Shroud for the mechanical fan in good shape - well not broken?

lawsoncl

Torque converter locking up? If not, that will add a ton of heat fro the slipping.

IJM

Good questions to be asking, but if it's only overheating at speed, it's not an airflow issue. Sounds like the water pump may be the culprit.

That Jeep Guy XJMJ

airflow is just as important as that waterpump functioning, you couldn't get away with Just a good waterpump if you covered the entire front of the rad with cardboard could you?

GreyJeepy00

Hey Sorry I forgot to include that in my list, I replaced it almost exactly two years ago 8/27/2022 at 234068 miles, I’m currently at 247100 miles, it was a autozone duralast replacement, only reasons I used duralast was because it has a lifetime warranty replacement on it

GreyJeepy00

Funny you say that, January of this year my tranny started slipping and bang shifting in 1st and second, 241316 Miles, I have a well trusted Transmission shop that has rebuilt many of my Irocs and T/As trannys, they did the job as they recommended a full rebuild, about two months ago I was having a problem were it would keep shifting in and out of overdrive at 40-45 mph it would just keep jumping in and out of OD and was hard to accelerate, I brought it back and they fixed it, supposedly it was a sensor on the tranny, recently I had a pending code for PO740 Torque Converter Solenoid Circuit Open, Also a persistent and worrisome Banging when coasting downhill at 30 MPH, also I noticed some seepage of ATF on the tranny, I brought it back they said something with the Valve body was leaking and repaired it “no more leaks” but they couldn’t do anything about the code because it was no longer pending and I had no CEL, they told me drive it and if it comes back just drop it off ( i have a two year 24k mile warranty on the tranny)

New 4 Seasons Fan Clutch at 237726 Miles
Fan shroud is still in place and only retains one small crack on the corner of it

lawsoncl

Easy test for lockup is while cruising along on the highway, tap the brake pedal with your left foot enough to trigger the brake light. That also triggers the trans computer to unlock the t/c, and you should see the rpm come up a few hundred when it unlocks.

IJM

You get all the airflow you need from driving down the highway, unless the grill is blocked or something. It's at slow speeds where those fans are so important. However, the OP said it's fine around town and only overheats on the highway, so we can eliminate the cooling fans as the main culprit.