Creeping overheat issue

Specs: 93' Sport, AW4, 4.0 HO (114K on the clock), bone stock.

radiator and water pump are 5 years old, fan clutch is new.

Recently i have noticed that my temps are climbing during normal driving/idling. if i sit at a light or just let it idle my temps will get to 230 or so pretty quick, but haven't red-lined yet. First thing i noticed is that my e-fan doesn't kick on at the specified temp like it should, but if i turn my AC on, it kicks on and then my temps go back to normal and pretty much stay there. I did notice today that when i turn it off to run into the store when it is hot, i come back out and start it up and the efan kicks on to bring the temps back down, weird...

so before i throw parts at it, wanted to get your opinions on doing a prestone flush kit on the radiator and putting in new coolant (current coolant looks fine though).

From the searching i have done it seems more than likely it is time for me to change out the rad and water pump, but money is tight and i would like stave it off for a bit longer if at all possible...

on a side/newby note. i have a stuck lifter and i have heard seafoam could help it out, do i just pour it directly where you fill it with oil (few days?), run it for a bit then do an oil change (i think that is right at least... lol)

Happy friday!

Hallo. A new CTS (Coolant Temp.Sensor) is more what you need imo.
When the coolant is still clear of color, it is no need to flush the rad. or renew the rad.
Only the renew the coolant is a good idea.(each 2 years for an iron block)


p.s. For the sticky lifter, I had a good result with a little bit of ATF in the fuel for a few miles. Change the oil
filter after that too!

'92 XJ wim

ATF in the fuel? How do you do that for only a few miles? I suspect you misspoke and meant oil...

OP - Is your thermostat good? Perhaps your water pump impeller has worn out to the point that it's more of a blender than an impeller?

EDIT: also check your viscous clutch on the mechanical fan. Run the engine up to op temp, TURN IT OFF (unless you don't want your fingers), and see if you can spin the mechanical fan with your hands. If you can, get a new clutch unit.

For the lifter, I would add some Marvel Mystery Oil to the crankcase. You just add it in and can keep driving until your next oil change instead of having to waste the oil and filter.

You could try Wim's suggestion and see if that changes the readings on the temp gauge.

As for the pump and radiator, 5 years is about the end of the life for a water pump. I would change it and the thermostat. If the coolant tests good, drain it into a bucket and save it. Get some commercial flush for the radiator, the kind you put in and drive for 500 miles or so, follow the directions.

I don't know about your fan clutch. The symptoms you describe would seem to be a bad fan clutch. Is it a standard XJ or did you do the ZJ HD fan clutch upgrade?

kastein said:

ATF in the fuel? How do you do that for only a few miles? I suspect you misspoke and meant oil...

OP - Is your thermostat good? Perhaps your water pump impeller has worn out to the point that it's more of a blender than an impeller?

EDIT: also check your viscous clutch on the mechanical fan. Run the engine up to op temp, TURN IT OFF (unless you don't want your fingers), and see if you can spin the mechanical fan with your hands. If you can, get a new clutch unit.

Click to expand...

:anon: I meant in the oil, indeed.

stupid wim

Changed everything but the heater core, and upgraded several items, still have the heat creep!

Sounds to me like he might have an air bubble In the cooling system. After changing all the suff you described it is possible. Did you use a thermostat that you bought @ Checker, AutoZone ect.? If so it does not have the weep hole drilled in it like the thermostats you get from the Jeep dealer.

hi all, OP again.

So the fan clutch is new (within 3 mos), but once i get it up to temp, then turn it off, i can still spin it. it isn't too hard to spin either, so maybe i got a faulty one (standard one from Adv Auto, not ZJ HD).

another thing to note. once i get moving again, the temps go back down to normal again very quickly. so i don't know if the temp sensor is bad unless this is a sign.


But since all the cooling system except for the clutch fan (suspect bad??) is old, it just might be time to at least do the t-stat, water pump, flush the rad (or replace) and then i should be good (LOL, in theory!)

For the sticky lifter, i will try some ATF in the oil, how much should i use?

Thanks for all your help!

I'd go with Mystery Motor Oil or Liquid Wrench. A can of LW fixed badly clattering lifters for me 30 years ago, so thats what I'd do again.