Yet Another Hot Running 89 Xj....help!!

I have an 89 XJ Limited, 4.0 with A/C. I put a new thermostat (from the dealer) about 2 weeks ago. She still ran hot and was blowing out coolant from the bottle. Then a couple of days later I topped her off with coolant and ran fine....didnt event overflow. The temp gage would go up to 210 and then a min or two later slowly drop down to about 180/190 and cycle like this while driving. Now I am right back where I started again. It can be 100+ outside driving with the a/c on and the temp gauge will stay at 210 or just a little below for the 40 mile drive to work. Once i get off the highway or I am in traffic my temp starts climbing above 210 inching towards the red. What has me confused is that if I leave the a/c on and can keep moving even slowly in traffic the gage will cycle from 210 to 180/190. But if I am at idle the temp constantly rises. Today I tried running the defroster on high heat so I could have the aux. fan running and help dissapate heat from the coolant.......IT HELPED QUITE A BIT I DIDNT OVERHEAT AND GOT THE TEMP BACK DOWN TO ABOUT 190OR A LITTLE HIGHER. I dont know what to try next. I know the water pump is good as for the new thermostat. Try burping the system constantly but will still run hot.

ANY IDEAS ON WHAT TO DO??????

Check to make sure the electric fan is turning on and off.

I have an '89 xj. I ended up changing mine over to an open system with a 3 core radiator and put the electric fan on a switch under the dash. It cured all my heat problems and I tow and plow with mine.

There's a good writeup here if you go that route.

http://www.off-road.com/jeep/cherokee/98/12_dec/radiator/radiator.html

the electric fan is working......turned on a/c and defroster.....saw elec. fan star to run.

RenoHogHead said:

the electric fan is working......turned on a/c and defroster.....saw elec. fan star to run.

Click to expand...

You probably just need a new radiator. Stock isn't very effective when it's clean and shiny inside. Get years of scale/crud insulating the metal from the coolant and you have the trouble you describe.

I used a CSF all-metal 3-row and replaced the tank/cap plus all rubber. Renix likes a 190-195 thermostat and I couldn't justify all of the other mods to go open when the closed system works fine with everything to spec.

There are a couple of "tricks" to servicing/filling the closed system like refilling through the upper hose pulled from the thermostat housing so that the system fills through the radiator to engine from the bottom-up to prevent trapped air. Another is don't use thread sealant on the e-fan switch inside the rad. It has an o-ring and sealer seems to insulate the switch/sensor enough to cause erratic operation.

BTW - look for signs of headgasket/compression leak into the cooling system but if it looks good, it's probably just the radiator that needs R&R.

One oft-overlooked problem with that era is the overflow bottle - people want to crank the cap on but that splits the rubber gasket inside the cap, causing it to lose pressure. If you've done this or if the rubber gasket looks 'iffy' get a new one. I don't think they're available separately though, so when you buy the new overflow bottle do a few things before installing it:

1 - clean the threads on the bottle. Just run a knife around the edges to remove the plastic flash from the injection molding.

2 - Pad the shelf that the bottle sits on. I used a section of old radiator hose that I'd split in half. Years of vibration from the engine will crack the bottle or the lower tube.

3 - Make sure that lower tube is free of the edges of the shelf. Once again, vibration kills.

4 - Don't crank down the cap...just turn 'til it's seated.

5 - Fill to the middle of the post in the bottle. The post is notched; full is when the top of the post is submerged (when it's hot, I believe?) and you want to keep the level between the top and the solid portion of the post. When the thermostat opens, you're likely to have a considerable amount of fluid exchange so be prepared to fill it again and again.

6 - Take a look at http://www.yuccaman.com/jeep/cooling.html and see if I missed anything.

I had an 89 with the same problem. One of the crappy things about the 89 is the way the cooling system is setup. When you drain the fluid and fill it back up, you must "burp" the system, or get all the air out of the system. You cant see how much is in because of the close radiator. If you have air in there, its not going to be able to flow and hold the right amount of fluid needed. If you dont know how, Pm me and ill give you some help. My advice would be to make sure you have put enough fluid in there and burped the system before you change out the radiator. Start simple.

Another thing to check if you're overheating at lower speeds and/or in traffic is the fan clutch. Get the rig nice and hot, drive it around town a bit, then stop and shut it off. Try moving the fan, the clutch should be pretty stiff and you should have a hard time turning it (if you can at all). If it's loose or very easy to turn, you probably need a new fan clutch.

on an '89, if you still have the original radiator, it's way past due for replacement. My '87 has the original radiator in it as far as I can tell, and it's being replaced tomorrow because when it started getting warmer out I started noticing that the temps were climbing above my comfort level when ascending steep/windy roads into the woods or to the trails and such. I'm hoping that with the new radiator, a newer fan clutch (replaced a few thousand miles ago), and a complete system flush, I should be back to the days of a steady 200 or so on the gauge no matter what. We'll see tomorrow.

RenoHogHead said:

the electric fan is working......turned on a/c and defroster.....saw elec. fan star to run.

Click to expand...

There is a temp sensor in the radiator that controls the fan as well. It's on the driver side, rear, about half way down. If you disconnect the harness and jump across the contacts in the main harness (not the one connected to the sensor), the fan should come on. If it does, your sensor is likely bad. You can hook an ohm meter up to the sensor contacts. When cold, it should show an open circuit. Once hot (about 210 or so), it should show continuity. You can remove the sensor and put it in a pot of boiling water to be sure.

Fan clutch is another cheap item to start looking into, as mentioned above. I just replaced mine on my 96, and you can feel the difference when the hood is open, by the amount of air it blows out.