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thermostat possible

3K views 25 replies 15 participants last post by  filluptrk 
#1 ·
I am stumped..
Changed the thermostat recently, the radiator, the fluid, the water-pump, and its still getting hot at idle when I sit for a small period of time. When im driving its fine because the air flow of coarse but I don't know what to do next or if there is anything..

Could it be anything with the transmission or is that rare?

Thank you in advance!
 
#8 ·
The mechanical fan will spin/run as long as the engine is running......that doesn't mean that it's functioning correctly and drawing adequate air thru the rad. It could be excessively free wheeling because it's old and worn out.......but it will still turn/run/spin, even when shot.:thumbsup:
 
#12 ·
The ZJ HD fan clutch NAPA number is 272310. I have one on each rig, not noisy, no overheat...ever! I believe it cost $45. Well worth it.

Don't let them try to sell you a MAX COOL fan...it will NOT fit.
 
#13 ·
thanks alot for all your help! Im going to get the fan clutch from napa and try the hole in the thermostat if it doesnt have one ( any pictures of that btw?) and i have to replace the valve cover and rear main seal....
 
#14 ·
I might have a spare one at home that I'll take a picture of tonight. It might just be easier to buy one at the dealer or Napa since they don't cost that much. IIRC, the hole is at 6 o'clock on the t-stat when installed.
 
#20 ·
As others have said, replace the fan clutch. Just because the fan turns doesn't mean its turning fast enough- that clutch needs to engage HARD when the temperature starts creeping up. Under normal conditions and with a good fan clutch, the electric fan should only be needed when you're running the A/C or in *very* hot weather without A/C.
 
#21 ·
same thing happened to me recently. radiator was fairly new, so i changed out the water pump, t-stat, upper hose and flushed/filled the coolant. Also added the aux.. fan switch. STILL overheating. couldn't figure it out... until...

i had a second set of eyes go through the whole thing, and realized that that i didn't "burp" the system. there was a lot of air in the system. once i got it all out, i've been fine since. temp holds steady at approx. 210.

could be something as simple as that. hope that helps...
 
#23 ·
Probably. You also can just get a stock replacement one, it worked fine untill it wore out, so I imagine it would work fine again :).

FWIW my 10 year old stock fan clutch keeps the temp about 195-200 or so unless I am towing something. And my AUX fan pretty much never turns on, even when towing. There is something to be said about a nice clean radiator. Oh, and the shroud around the fan does make a difference, if yours is missing they are not expensive.
 
#24 ·
I show different numbers for them from the ones I got on my 2000. But all you want to do is to look at the 2.5 next to the 4.0 and compare. The 2.5 will be a bit taller around 1/4" or so but should fit fine. Just be sure that it is not right up to the radiator fins, that won't work at all. Make sure also that the A/C condenser is not plugged up with junk. None of what you did already will help if the air to the radiator is blocked by poor airflow through the A/C part.
 
#25 ·
I'm dealing with the same issue on the XJ I just purchased. It runs great, steady around 210 or less, but if I get stuck at the second stoplight in a row, it starts to climb. I'm gearing up for a coolant flush this weekend and will replace the thermostat at the same time. I am also thinking the fan clutch is wonky. Will replace that, too. We ran it for a while in the driveway to see what happened when, and the mech fan ran like gangbusters while it was warming up. Put out TONS of air. It hovered at 210 for about 5 minutes, then it started to climb. The efan didn't kick in until around 230, and the mech fan slowed down so much that I could almost make out the individual fins. I can't figure why the mech fan would run so hard while it was warming up and then crap out when it was really needed. Any ideas?
 
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