motor heating up issue

ok to start its a 1990 converted to open cooling system. it works beautifully if im moving even a little but when i stop it starts to heat up to about the 3rd mark never hotter. it does it even when the aux fan is on. my question is my brothers x-terra used to do the same thing his timing belt went out while it was appart a new water pump was put in and now it doesnt do it, so should i try a new water pump since mine shows the exact same symptoms? i really dont trust it going up that high on the temp

First thing is to figure out the real temperature it's running at. If it's not over 220, you are good.

Ok, sounds like the mechanical fan clutch is getting tired.

If when you are stopped and the temp starts to climb, does revving up the engine bring it back down? Yes--replace the fan clutch.

Quick and dirty fan clutch 101: when cold, the silicone fluid seeps out of the reservoir, so when the engine is first started the fan will engage until the fluid is forced back into the reservoir. So, check the resistance of the fan when turned by hand first thing in the morning--it should be a little stiff. Then run the engine for 5 minutes and shut it off--turn the fan by hand it should be a little easier. Now, run the engine for 20 minutes, that should allow the air hitting the bi-metal spring to warm it and fully engage the clutch--it should be very stiff to spin by hand.

hmm seems like it may be my fan clutch i drove it around for 20+ and its still has just the fluid feel to it when turned. but the only other thing is that even with the electric fan on it will still heat up like that. the electric fan makes absolutely no difference on the temp

ok ya did another test run its 90* out and its for sure fully warmed up. i can hear the fan spin up just behind my rpms and fall just after them so it seems to be fine. when i push it it only does about a quarter turn and stops the fluid feel seems fine compared to other fan clutches ive dealt with. im pretty sure the fan clutch is good i can tell its a replacement one a previous owner must have put on at one time. usually when im 4x4in in 4low if my rpms are up a bit (doing like 3 mph but higher rpm) it easily stays normal just below 210 but as soon as its idling it climbs near 3rd mark within a minute. i want to think its the water pump just because even at idle and with elec fan on it still does it.

Stock electric fans are WIMPS when it comes to moving air, and if yours is tired that would just complicate the issue.

If the fan clutch free wheels when hot it is toast.

You can upgrade to the ZJ HD fan clutch, NAPA number 272310, it is a direct fit replacement for the XJ fan. It will make noise when engaged as it moves 80-90 percent of shaft speed compared to the standard clutch's 60-70 percent when engaged, but it will keep things way cool--kind of hot out there in Apple Valley, isn't it? If you decide to do the upgrade, don't let them sell you the ZJ MAX cool clutch, it WON'T fit.

1990heepxj said:

ok ya did another test run its 90* out and its for sure fully warmed up. i can hear the fan spin up just behind my rpms and fall just after them so it seems to be fine. when i push it it only does about a quarter turn and stops the fluid feel seems fine compared to other fan clutches ive dealt with. im pretty sure the fan clutch is good i can tell its a replacement one a previous owner must have put on at one time

Click to expand...

Ok, but keep an eye on things--your symptom screams fan clutch.

hmm well now im confused i dont wanna put this water pump i bought yesterday on if its not gonna help. although like i said my brothers xterra used to do exactly as my xj does. it heats up at idle or when turned off after driving it how should the pully wheel on the water pump feel when not just turned free hand obviously with no belt on it?

The WP should turn smoothly with a little resistance due to the coolant and the impellers.

It is normal for the temperature to increase after shutting off the engine--no air flow through the radiator so any heat exchange at the radiator is localized as the coolant isn't flowing, the coolant continues to absorb heat from the engine's metal.

Again, my biggest concern is your temp going up at idle/slow traffic and that is when you need the fan the most. The bi-metal spring on the front of the clutch starts to open the reservoir valve when the air hitting the spring is at 170 degrees, and the coolant in the engine is about 30 degrees higher.

Fan Clutch. Replace per Joe's instructions.
Aux electric fan, go to PnP and grab one off a 1998+. Instead of straight flukes the fan will have them swirled. The latter design moves more air.
You have a shroud in place? without a shroud the fan is just causing confusing air movement in the engine compartment.

I say fan clutch and make sure they system and cap is holding pressure, make sure the cap isn't venting early either.

well it only does it at idle, in slow traffic it stays nice n low just below 210. yes i do have a fan shroud. the heating when i shut it off i understand i just dislike it goin up when i stop. the caps holding pressure like it lets out a hiss as its opened. the fan clutch feels fine tho and i can easily hear it roar up with the rpm of the engine, its really not showing any issue with it other then a symptom that could be possibly caused by it

Yeah but make sure its not venting early, you need a radiator cap pressure tester. Its a little pump you can use to pressure test your cooling system and other components. Most people don't have one, they are around 100 bucks give or take for the whole kit and its cheaper to just buy a new cap and call it good. I've got one because I'm a auto tech so I need it for work. What happens is as you pressurize coolant its boiling point increases so even if your cap holds pressure if its weak then the boiling point of your cooling system will be lower. Basically you get air pockets and hot spots and that causes the gauge to fluctuate a lot and could be causing your problem or be a contributing factor. But as everyone seems to state before air flow obviously is critical too. I guess what I'm getting at is it doesn't take much to really reduce your cooling systems ability to cool properly so don't over look any small detail.

well i dont know but i drove around for 20+ mins then it just sat for about an hr the fan seems to spin way easier then my brothers xj's fan does although his is completely cold. i think ima take back this water pump and get a fan clutch instead. also the radiators pretty new probly less then a year so i doubt the caps bad

My vote's for tossing on a new rad cap as well. Mine was newer, and a #16, plus it worked perfectly all of last year; but this year my temps were doing the same thing - they'd creep up in stop and go traffic, or while idling. I was worried about what might be wrong, so I read up on here about folks with similar problems, and tried both a new rad cap & some water wetter.

On the test drive the temp was slower to go up, and then hovered right between 105 and a touch below 100 degrees (Celsius, since it's a Canadian Jeep.) I'm pretty sure it was the new rad cap, since the changes were before the rad had a chance to mix in the coolant from the overflow tank. (Where the water wetter was.)

What is your current radiator cap rated for, BTW? Is it a 13#, a 15# or a 16# rated cap?