factory cooling

I have a 94 XJ with a 4.0 and I am just wondering how the temperature actually is supposed to behave when idling in hot weather. I have replaced the thermostat with a 180, chemically flushed the radiator twice (in good shape I think because highway driving the jeep runs around 190 to 200 no matter what), have a relatively new water pump, and just yesterday replaced the fan clutch. It seems as if the system is in good shape for its age, yet as it sits idling the temp will raise to about 220 or so then the electric fan comes on and slowly lowers the temp. Am I making a bigger deal out of this than it really is? I would like to know if they are actually designed to run hot like this. Thank you for any input.

Sounds normal to me.

My 98 with 270,000+ miles just got a new water pump, hoses, belt, tstat and it too has started to creep up over the center mark. Not liking that one bit at all, last summer I could crawl all day in 4lo 1st and 2nd and the temp gauge would stay rock solid and never budge above that line. That said while I was doing the water pump and hoses last month I did break the bottom of the fan shroud off, the piece between the two bottom tabs but the tabs still lock in. The broken piece is just a blank filler prettymuch cut to fit the fan for clearance. Soon as I'm back out rolling again the temp drop to normal and stays there. Where did you get your fan clutch from ? The other question is, does your fan 'roar' in the morning when it's cold ? I noticed, anecdotal evidence for sure, that good clutches 'roar' for about 30 seconds on a stone cold startup, I noticed mine has stopped doing this and it seems to have coincided with the heat build up.
I just this morning ordered a new fan clutch and shroud from the dealer, hopefully it will be here by friday as I need to get this fixed before next thursday when I will be getting PAID for working at camp jeep at Big Boulder for 4 days. Otherwise either my son or daughter are going to be driving my XJ while I use one of the TJ's....

pauldo39 said:

I would like to know if they are actually designed to run hot like this. Thank you for any input.

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Yes.

Aux fan comes on at 217 degrees.

And there is no reason to run a 180 degree thermostat. An automotive thermostat is designed to keep the temperature UP, not down. If the factory engineers had wanted the engine to run with a 180-degree thermostat, that's what they would have used.

Thanks everyone for your input. RichP, I got my clutch from Napa, I like the guys there a lot and have had way more luck there than advance or autozone. Since it's really hot out and the garage is always above 85 when I park at night, I haven't really heard the clutch roar on a cold morning, but I do know what you mean in the winter, when the jeep is sitting in 10 degree weather. My clutch seems to engage when warm. Are you saying that when you broke the bottom of your shroud, it performed better? When I took mine off to remove the clutch, it appeared to be unharmed. The reason i'm using a 180 thermo is because my old one stuck and all the mechanics around suggested a lower one for the summer instead of the 195. I'm only 18 and just starting to really get into performing my own repairs, so I appreciate all the help and advice you guys are giving me.

pauldo39 said:

Thanks everyone for your input. RichP, I got my clutch from Napa, I like the guys there a lot and have had way more luck there than advance or autozone. Since it's really hot out and the garage is always above 85 when I park at night, I haven't really heard the clutch roar on a cold morning, but I do know what you mean in the winter, when the jeep is sitting in 10 degree weather. My clutch seems to engage when warm. Are you saying that when you broke the bottom of your shroud, it performed better? When I took mine off to remove the clutch, it appeared to be unharmed. The reason i'm using a 180 thermo is because my old one stuck and all the mechanics around suggested a lower one for the summer instead of the 195. I'm only 18 and just starting to really get into performing my own repairs, so I appreciate all the help and advice you guys are giving me.

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I don't know if the missing bottom of the shroud is good or bad, what I plan on doing is replacing the fan clutch and seeing what happens. If the temps keep doing the same thing I will put the new shroud in but I LIKE the bottom broken off, it is soooo much easier to remove so I can blow the radiator fins out from behind with out that pesky bottom getting in the way

The 180* tstat will only make it take longer to reach operating temperatur by opening earlier. Negative side is you may stay in cold loop a bit longer and waste more gas because the computer controlled system is making it run rich a bit longer. No matter what the temp of the tstat is they ALL flow the same amount of coolant when they open, a 150* would not flow any more coolant than a 190* will.

Rich P,.... I'd like to hear the outcome of your fan clutch install. Like it was stated earlier, I too have a relatively new NAPA fan clutch and I NEVER here it "woosh" first thing in the morning at startup. You were helping me discover the source of my overheating about a month ago. Ironically/coincidentally replacing the cat seemed to bring the temps down a bit but it still can get up to around 225 at idle in 94 degree outdoor temperatures.

Before the aforementioned accident, the temp guage might as well have been painted on at 210 degrees. It never budged. The same holds true with my 96 4.0 ZJ.

Make sure the belt's tight.

Hey guys, just my 2 cents.

Hot summer here in Buffalo, almost every day over 80. I cut hood vents in my truck about 2.5-3 months ago, and they help a lot. Even crawling in traffic, the temp guage takes forever to rise. You really have to be horsing on it to get the temp high enough to get the electric backup going.

I still find the cooling system marginal, because if I'm crawling in stop-and-go traffic for long enough, eventually, the backup kicks in. This could just be simple thermodynamics (air cools less the hotter it is), but again, my $.02.

Hood vent install doesn't look terribly good with 2 aluminum siding vents, but for around $2 for both of them + time/labor cutting and installing them, with my nephews watching, it was well worth it.

My belt was replaced and put on at a trusted mechanic about a month ago, so I'm pretty sure it's ok, it doesn't squeal or seem to slip at all. RichP if what you're saying about the tstat is true, then come cooler months I'll probably put back in a 195. This may sound like a stupid question, but approximately what temperature does the first white line represent after the middle mark, before the red? It seems to be right in the middle of 210 and 260, so logic would dictate it would be 235 or so, but my electric fan (without a/c on) doesn't seem to come on until at least 225 according to that scale, and it's supposed to come on at 217? Of course, 100 to 210 is the same interval as 210 to 260, so I don't know. If that white line is 235, could that mean that the coolant sensor or gauge is off, or the electric fan isn't reading the right temp?

Keep in mind that your temperature guage is not a scientific measuring instrument but closer to the likes of a $4.00 part.

While on the topic of "wooshing fans".... Since replacing my fan clutch it is noticably louder upon acceleration (like the higher the RPM the louder the woosh) It's just louder now that I replaced it. Seems to work fine, but is annoying, I liked the engine rumble sound better. Just one more noise I have to get used to on the Heep.

Aftermarket ECUs usually require 180* tstat, certainly the Mopar flash did. I think this results in cooler/denser air since the engine (theoretically) should be running cooler, and doesn't heat up the incoming air as much (through the intake system, manifold, etc.). This allows the spark to be advanced a little extra too (I think), and certainly means more fuel is needed to maintain stoichiometric 11.7:1 or whatever it is, for more HP.

Trade-off is that the water pump moves a hell of a lot more coolant, which of course is not free energy, so you really should upgrade your ability to dissipate heat along with the tstat changeover.

Another big plus (if you have relocated your IAT) is that the timing gets advanced a few degrees and the motor runs a little richer, even w/o use of the flash/replacement ECU, because you get a more accurate reading of the air temp as it enters the motor. Go to www.jeep4.0performance.4mg.com for more info on the IAT relocate.

My belt was replaced and put on at a trusted mechanic about a month ago

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A new belt will stretch and requires re-tightening after a couple of 100 miles..

I think I will go back and get the belt tightened... any idea how much this costs? can't think it's too much... i'm still wondering about that coolant gauge... I'm trying to decide if there are any sensors/senders to replace; before I waste anymore time worrying about the cooling system in the first place. If my gauge is wrong and the aux fan really is coming on at 217 or so, I'm going to completely stop worrying about anything because then the system is fine. Thanks guys for all the help.

A good place shouldn't charge you again to re-tighten it. I still don't think you have a problem.

A new belt goes on at 190lbs using a tension gauge, a used belt goes on at 160lbs. A new belt is defined as one run less than 15 minutes, used belt is one run more than 15 minutes. That tells me the belts stretchy FAST once they are on and have been run or heated up. You can spend $15 at NAPA and get a krikitII tension gauge that will remove any doubt as to your belt tension and it fits in your pocket like a thick pen. It's a handy item for the pocket and tool box.
You model year differs just enough, belt tensioning is one, on my 98 it is 'loosen one idler bolt a hair, adjust belt tension bolt to correct tension, tighten idler bolt' done. I think yours has a couple of other bolts that need to be done but I'm not positive. I can't recommend strong enough that you invest $100 and order the factory service manual from the back of your owners manual or from the dealer, it is worth it's weight in gold and can pay for itself in just a couple of uses with step by step procedures of everything for your year and model. The chiltons and Haynes are closer to cliff notes and they cover 20 years on one book an 1/8 of the size of the Factory service manual which is the size of a city phone book. I have one for my 98XJ and one for our two 97TJ's and they get used all the time. I had to put the kabosh on a couple of my sons friends from borrowing them, they can use them but they do the work HERE and the book does not leave the property without a $100 deposit CASH. That nipped that problem in the bud...

$100 deposit? wow that thing must be pretty valuable! I agree with you, I saw one of those chiltons at borders for 25 and bought it thinking hey at least it's something, and it has helped for some minor things, but it's not in depth enough, at least for someone like me without a lot of experience, for some more complicated issues. I think I may very well get the factory service manual. As for the whole cooling issue, I'm gonna trust everyone when they say my jeep is fine; I'll see if the belt needs readjusting, look at the shroud, and leave it at that. (i'll trust my aux fan is coming on at the right time). Once again, thanks everyone very much for all the input, I appreciate it a lot.

Paul

I'm somewhat in the same boat you are in. I really don't think technically you or I have a problem as long as the temp doesn't go over 220 degrees or so and most of the time it is at or below 210. BUT temps going up to 220 degrees from what i understand is the upper limit and not ideal. Ideally the cooler the engine runs, the greater the longevity of the oil and less wear and tear on engine parts. Am I right on this folks?

Here's how you tighten it yourself:
1) Get a 5/8" socket and an 8mm
2) Remove electric fan using 8mm socket, there should be 2 screws at the top and 2 clips on the bottom, but it will pull right out of these and also slide right back in
3) Loosen idler pulley using 5/8" socket until it is just about to come off
4) Use 5/8" socket to tighten the adjuster (righty-tighty applies here - the belt will be tighter if you turn clockwise, counter-clockwise to loosen)
5) Re-tighten idler pulley, reinstall electric fan

Takes about 15 minutes in good light, 45 minutes if it's late at night and your light-holder has other things on his agenda (like when I tightened mine last night).

There was a post around here on a good rule-of-thumb. I don't remember what the definitive answer was, but my auto teacher taught us that there should be about 1/4" - 1/2" of deflection between any 2 points 12 inches apart. On my XJ, I tend towards the 1/4", as I splash through a lot of wet stuff.