Well the past week my temp has fluctuated however it hasn't gotten waaaay hot. I let it run with hood open at operating temps and elec fan never kicked on. So this morning I tried to run my defrost like a guy on here told me to try and sure enough the temp stayed normal and when I parked the elec fan was kicking on and off as it should. Soooo why wouldn't it be doing it without the defrost running?. My t stat is new, water pump is new. New radiator. So this thing should cool! Lol

 

Could u give a few more details? Factory preset for fan on is 218F coolant temp OR whenever a/c compressor engages.

 

Sure, while driving my operating temps since new radiator has been 190 to 210 depending on how hot it is outside. I noticed it would run a little warmer and when I would get to where I was going I opened the hood and let it run and the fan never was kicking on at operating temps or a lil above. This morning I ran my heat cuz its cold out and had it on defrost and when I got to work the elec fan was working and kicking on and off. So I'm not sure why it hasn't worked as it should prior to today

 

If a/c compressor is not engaged or coolant temp has not reached 218F, efan will not be on. In cooler weather, say below 90F ambient, I wouldn't think coolant temp would reach 218F, so that leaves efan coming on only when a/c compressor is engaged. Verifying coolant temp with a infrared temp gun (pointed at t-stat cover) vs going by the dash gauge would be beneficial.

 

Not trying to hi-jack this thread, but I am having similar issues with my '89 XJ. Temp gauge almost hit red zone about a week ago after hauling 2 motorcycle on trailer and back was crammed with stuff during recent move; it was cool at night and I took it easy on the highway, temp stayed pretty normal at about 210 until I reached my destination and stopped letting it idle. Took me a few minutes to park my trailer and by the time I was done temp needle had continued to climb until it was dangerously close to the red zone.

I think I may be losing a little coolant too, but can't find any leaks; ran a combustion leak check yesterday, and the results were negative. Electric fan works when hooked directly to battery, but I can't ever remember seeing it go on automatically; just tried running it w/ AC on and defrost on and it still doesn't kick on. Not sure if AC compressor is engaging though (it has never blown cold air and I think the pulley clutch may not be engaging). Checked coolant condition too and it too seems good. It is currently idling in my driveway as I type this to see if I can get it up to 218 degrees (I have a laser temp gun) and see if it kicks on then. Will post back w/ results.

Temp seems OK as long as I am moving, but starts to creep up when stuck in traffic. Wondering if the thermostatic fan switch is bad, or maybe need a coolant system flush and/or new thermostat?

 

Cooling system maintenance? How old are cooling system components? One or several could be failing.

 

No idea how old the cooling system components are, it's got about 202,000 extremely well maintained miles, but there's always a high possibility for parts failure with a high mileage vehicle. Never a bad idea to flush the system and replace the thermostat while you're at it I suppose. Hoses look good though, and I can't see it leaking a drop of coolant anywhere.

However, after idling and wasting my gas for about 30 minutes, I could not get the temp higher than 221 F at the T-stat (and E-fan still didn't kick on); yet when I aimed my temp gauge at (what I am assuming is) the thermostatic fan switch on the radiator, the temp read 200 F. Should it read 220 at the switch before the fan kicks on?

 

If one has had an unexplained over heat and doesn't know how old components are, may be a good time to replace all components that involve draining the cooling system. Multiple drain/refills are a hassle.

 

Technically, it never actually overheated, but it had never gotten that hot before, and was pretty close to the red zone.

I drove it today for a bit, and it actually ran pretty cool, temp stayed at or below 200 F the whole time, even while stopped in traffic. It was a bit cooler today at about 85 degrees though, and I didn't drive too far, probably about 20 minutes each way. I don't mind replacing the thermostat because it's cheap and fairly easy, but I can't seem to justify doing the water pump unless I know it's bad. And I can tell with my eye and my hand that the hoses are in decent shape.

How can I tell if the water pump's going out? Will it start screeching, have play in the shaft, or does it have a "weep hole" that starts leaking coolant if it is bad? I'm leaning toward the electric fan thermostatic switch as the culprit.

 

Best way to tell if a unknown how old water pump is going bad is let it age naturally......place it in the box that the new water pump came in. LOL