xj cooling issues

ok my buddy has a 95 xj with a 4.0 and the aw-4 trans. as summer has heated up he has run into cooling problems. when the a/c is off it runs a little above 220 around town and increases slightly on the highway. when the a/c is on the temp rises even higher to the point of overheating so a/c is always out of the question. we flushed the coolant because it hadn't been done while he was the owner and it helped out a little but still have the same problem. i don't know where to start in getting it fixed and i was wondering if anyone here has a good idea where to start looking

thanks
-Doug-

I would start with the fan clutch, and see if the electric fan comes on when the A/C is turned on.

I know on my old 91, I went ahead and did it all. New radiator, fan clutch hoses, waterpump and mopar 195 thermostat. While it was apart I flushed water through all the jackets and made sure everythig flowed good. It never got above 210 again(I gave it to my neice 2 yrs ago and they say it still runs great without overheating in Florida) Maybe $3-400, depending on what brand names you go with and your problems will be gone.

I just got a new 4-row "heat buster" radiator for my 95, haven't put it in yet....but hopefully it will cool better than the one row I have now. I got it locally for about $180.

Hey Doug,

The first and most often overlooked part is the Radiator cap. I have a '94 and they are similar, but go to the dealer and get one. I have had the best luck with the OEM caps for all my vehicles. This is also the part that is sooo easy to fix-provided you haven't run the truck for about 6 hours(give it plenty of time to cool). I replaced my cap, and the thermostat and got the temp from going all the way up in the red section. I would go with a 160 temp t-stat and run an electrical check of the electric fan to see if it is even coming on. I think the temp sender for that doesn't always kick it on at the right temp. As for changing the coolant, did you do a reverse flush and flush all that stuff out backwards? Keep us posted.

Jeff

Definitely check the engine fan. If it's original the viscous fluid has probably crapped out. See if the front of the fan is all oily. There's another way to check but I forget. HTH dn

tsgolo said:

Definitely check the engine fan. If it's original the viscous fluid has probably crapped out. See if the front of the fan is all oily. There's another way to check but I forget. HTH dn

Click to expand...

Spin it by hand, if it spins easy it's kaput.

Couple of things based on my experience...

I have an '87 that currently has serious overheating issues.

1) I suspect the tranny needs serviced (new fluid and filter). The indication that leads to my suspicion is that whenever I drive at higher RPMs, like pulling a hill or downshifted into 3rd at cruising speed instead of OverDrive, the engine overheats. I fully expect that sludgy fluid and/or a clogged filter will contribute severely to overheating given the fluid is run though the drivers side of the radiator to dissipate heat via the cooling system (which ironically is on the same side the engine pulls water from!) My AW4 has the Power/Comfort switch which adjusts the shift points. I notice the difference but it also causes my cooling system to overheat faster on the "Power" setting.

2) I replaced my radiator cap with a brand new special ordered (it's not a regularly stocked cap) Stant 10252. (for the closed cooling system water bottle.) The truck overheated much sooner and I promptly threw that new cap in the trash and replaced the original stock cap.

3) I have read on several other posts that the manufacturer recommends replacing the radiator at 150K miles. I have 165K and another person mentioned theirs started acting up at 160k as well. I have yet to replace mine, but I thought about removing the radiator, laying it flat and filling the tranny cooling module in the radiator with a non-flammable solvent, letting it sit for a while and blowing it out with compressed air at about 20 PSI. My thinking is that perhaps there is buildup that is making the heat transfer inefficient allowing the tranny to get too hot.

4) Radiator Hoses. Primarily, you will want to ensure the lower hose is good. It should have a spring in it to prevent it from collapsing. Make sure they are all in good condition and don't have any soft spots or spots where they are bulging. I replaced the upper hose but the rest are in great condition.

5) As for the fan clutch. I read on another post (not my knowledge here...) that for the price, you're well advised to replace the clutch every 3 years. Someone not too long ago posted a link to a site where you can get a solid mechanical replacement for the clutch, making the blade a direct drive. That kind of setup would make a lot of noise constantly as the fan runs at the full pulley speed. The clutch regulates to some degree the speed the fan runs limiting some of the fan noise.

6) The electric fan... I suspect my thermostatic switch that triggers the electric fan on my jeep is flaky. The fan is known to stop running when the engine gets hot. Turning on the A/C switch will turn the fan on but it's too late at that point.

7) Speaking of A/C... I noticed the vanes in the A/C heat exchanger were clogged with sand and some bird feathers. It isn't that much work to take the upper plate off from above the radiator and using an air compressor, blow the crud out of the vanes. Better air flow leads to better cooling. I removed my heat exchanger altogether and didn't notice an improvement. I will be reinstalling it and getting the A/C serviced ASAP since we were 99 deg. today here in Denver!

8) Thermostat. Make sure you're running a new thermostat and that it's installed right. When you open up the cooling system, you allow air into the system. Air is your arch enemy. Drill a 1/8" hole through the flange on the thermostat near the edge that falls just within the waterway and when you place the thermostat into the block, position the hole at the top. This 1/8" hole will allow air to bleed out when you fill the cooling system. Air in the 'closed' cooling system is one of the hardest problems to overcome.

9) Some people have sworn by converting their Renix XJ's to an open system with a conventional radiator cap and boil over coolant recovery bottle. JeepNJoe has an article about an inline filler neck that will allow you to effectively convert the existing closed system to an open system. Actual Mileage may vary... [link]http://www.jeepinjoe.com/XJ_Tech/Open_System_Switch/open_system_switch.html[/link]

10) Fluids. Make sure you're running a 50/50 water and coolant. Several people are swearing by WaterWetter (sp?). I didn't notice a difference with it but my issues may just be too much to overcome with a little bottle of yellow fluid.

I will probably wake up at 2am remembering something I didn't include but that's all I can think of right now. Hope it helps someone.

Rob

yep, sounds like a hot tranny, get it serviced. I run water wetter and distilled while its summer, tho i dont have the aw4

Doug,
A local jeep guru here (long time jeep mechanic who works mostly on XJ's now) told me once that he had a jeep that overheated worst on the highway. What he did was to run a steamer through the cooling passages. He said that when they kept doing that, and blowing them out, all kinds of sludge and junk came out the back of the passages. If part of the block gets, well, blocked...you'll have symptoms similar to this me thinks. Hope that helps.

shortxjdoug said:

... it runs a little above 220 around town and increases slightly on the highway.

Click to expand...

That's the clue. On the highway, you don't need fans so you can forget about that.
You need a radiator. You just can't shed enough heat.

I am still thinking the cap. Again it is often the most overlooked and besides isn't the most expensive like the radiator or hoses and clamps for that matter.

Jeff

My 98 overheated on me yesterday sitting at the McDonalds drive through. That should have told me something to begin with, but thats a different story. When I checked under the hood, antifreeze was dripping out from around the ridiator cap. A quick stop at the local WalMart for a Staunt replacement not only fixed the problem, but reduced my normal running temp by about 10 - 15 degrees. Just my .02

my 90 cherokee would over heat ( I live in Phoenix 115 damn hot) but I got a radiator out of a 2001 with the 2 row alumnim (sp)? and it has never ran past half way on the gauge. I towed another jeep 50 miles in trafic at 113 out side with the a/c on with out a problem. you can buy them at the dealer for about $300 or used for about $150-$175

I have the same jeep as your buddy and I also seem to have his same cooling problem. I believe that I have the original radiator cap on it and I know my aux fan comes on, however I still overheat with AC on. Never any other time. I have 200k miles on it and I probably need new transmission fluid and maybe a new t-stat. Is it also time to replace the radiator and/or OEM cap? Everything on the jeep is original except transfer case.

Speaking of fan clutches, just how hard should it be to spin a good one if it's working correctly? I replaced mine '95XJ/4.0/AW4 with a u pull it unit that spins fairly freely (like my old one did) right after I open the hood and the temps been up to 220. Should I just buck up and drop the $70 on a new one?