Overheating '92 XJ

I am looking into buying a 1992 Jeep Cherokee. The body is perfect, The interior is perfect, Engine is a VERY strong straight six 4.0. It has a new computer, new water pump, new fuel pump, six disc cd changer, and a pretty sweet sound system. The guy I am buying it from is an electrician, but doesn't know a whole lot about engines. He has done all the work himself including a thermostat swap. The asking price is 750$. It has about 126K miles. The problem is that the coolant intermitantly overflows and then the jeep overheats. I havn't had a chance to troubleshoot it, and I know that the thermostat is easily installed wrong. I guess my question is, is it worth buying, and what could the random overheating be? Thanks for the help.

The Coleish 1
"without crew chiefs, pilots are just pedestrians with cool sunglasses"

for only $750 you better get it. then change out the tstat and swap in an electric fan from a junkyard taurus SHO and call it a day.

Is it possible that the overheating problem is a bad head gasket?

there is no smoke from the exhaust, no water, and the oil is virtually new after 2200 miles, still the yellowish oil color

Even with a cooling problem that is a very good price.

snatch it up!!

make sure thet there isn't an airlock behind the thermostat. I changed mine and had to force the air out of the top of the block to make everything work correctly. It is worth the price though. I have the same thing but paid 1500. The radiator may also need to be flushed if there is any buildup inside of it(could easily make it run hot).

Never really worked on XJ's before. How do you force the air out of the top of the block. And also how is the head gasket change on one of these. I change Head Gaskets on both sides of a 90 Bronco II 2.9L V-6, Took me about 8 hours. Seems like this might be easier being an I-6. Will 30X9.5 tires fit on a stock XJ? Thanks for all the insight and suggestions fellas.

I know they will fit on a stock Grand, not sure on the XJ. But they should.

I found this in forums and IT WORKS!!!! I've struggled with intermittent overheating for last six months. About once a month it would freak out for no decernable reason and then it would take me about 2-3 hoursand 3-4 gallons of anti-freeze to set it right.

I hope that BC BLues doesn't mind that I borrowed it.

"BCBlues
For all of you that have a pre 1992 Jeep Cherokee with 4.0 Ltr 6cyl engine. I have the solution to your cooling system wows. My Jeep Cherokee is a 1988.
The stock Pre 92 system is a closed system with no radiator cap and complicated plumbing for the heater core and the coolant expansion tank.
The problem with the system, as I'm sure your already aware.
1. The coolant expands and blows out of the expansion tank cap with no place for it to recover from.

2. The electric coolant fan switch is in a bad location and rarely turns on the fan when needed because of constant coolant loss leaving the sender un-exposed to coolant, and its location in the radiator is a cold spot because of the design of the radiator.

Remove the original radiator and replace it with a Modine NAPA # 2802 or equivalent. This radiator is listed for a 1992 Jeep Cherokee. This radiator is an open system exact fit and has a radiator cap/fill neck. All hoses and transmission lines will connect in the same place. This radiator does not have a provision for the fan switch (I will get to this).
The proper radiator cap for this unit is NAPA #705-1445

Remove the water outlet (thermostat housing) and replace it with the housing from a 1993 4.0 6 cyl Cherokee. This is a dealer or auto recyceler item. This housing is an exact fit with all of the hose positions in the same place. In addition this housing has a hole tapped into it for the 1993 temp gage sending unit. This is were you will mount a Fan switch to replace the one that was on the origional radiator. This new switch location has better heat transfer to the switch so the electric fan will cycle more frequently thus resluting in better cooling.
Since you have the housing off this is a good time to replace the thermostat.

You will need a Fan switch. I used NAPA # FS113, and the proper connecter to this switch is NAPA # FSC10. This will turn on the fan between 207-220 degrees. The origional radiator mounted switch activated at 230 degrees. As mentioned earlyer the new fan switch mounts in the 1993 thermostat housing.
The switch is a single pole switch with one wire and switches to ground so you will have to use a head light/horn relay to connect it to your original fan wires.

1. Run the new fan switch wire to the ground terminal of the relay.

2. Carfully cut off the original wires with plug from the original radiator mounted fan switch. Cut them off at the switch side so you have the plug with the wires attached. The yellow wire is +12V and the black wire goes to the original fan relay. Connect the wires with plug to the switched (load = yellow, output= black) terminals of the relay. Since the yellow wire is hot +12v when the ignition is on use this wire (make a jumper to connect to the + side of the relay) to power (activate) the relay.

Recap step 2. Yellow wire goes to relay + (positive) and relay load terminals. Black wire goes to relay output terminal. Fan switch goes to relay - (minus /ground) terminal.

3. Remove all heater hoses, coolant expansion tank and mount, metal y-pipes, and heater valve if your model has one. Be carfull not to break the plastic vacume line attached to the heater valve as it can become brittle.

4. Install heater valve NAPA #660-1174. This valve has 4 connections. Looking at the valve from the opposite side from the vacume switch with the curved end of the valve facing upward you will see one connection facing forward, two connections facing back and one facing at a 45 degree angle facing towards you. On the bottom angled connection run a 5/8" heater hose to the thermostat housing. On the single connection on the front run 5/8" heater hose to the water pump. Connect the two rear facing connections to the top and bottom connections of the heater core. Connect the vacume line that was connected to your old valve to the connection on the new one.

5. Purchase an after market coolant recovery tank and mount it in the hole were the old coolant expansion tank/mount was removed from.

6. Run a 5/16 fuel line or equivalant from the expansion tank to the fitting just below the radiator cap.

7. Fill cooling system using standard methods and precautions.
Parts list. I used NAPA auto parts as a source so all part numbers are NAPA numbers. These are standard replacement parts and can be purchased from any after market or dealer source.

1. Modine Radiator # 2802 for 1992 Jeep Cherokee.

2. Radiator cap #705-1445.

3. Coolant Fan Switch # FS113.

4. Fan Temp Switch Connector # FSC10.

5. Heater Valve # 660-1174

6. Water outlet from 1993 Jeep Cherokee (dealer only or auto recycler).

7. Standard 30amp Headlight/Horn Relay.

8. 8' 5/8" Heater Hose.

9. 10' 5/16 Fuel line.

10. Teflon tape or equivalant thread sealant for Fan switch threads.

11. Small roll of 12 gage wire.

12. Small package of 1/4" spade connecters to connect wires to relay terminals.

13. Small package of butt connectors to connect fan switch to wire going to relay.

14. Two gallons of Antifreeze/Coolant.

You will now have a standard open cooling system like every other car on the road. No more will you be stuck on the side of the road with an over-heated Jeep as the result of running out of coolant because of the Renult designed closed cooling system. When you add coolant to the new system you will know that your radiator is full because you fill the radiator now, and you now have an overflow tank that will return the expanded coolant into the radiator when it cools down (just like every other car on the road.

This conversion takes about three or four hours depending on your abilitys. Show this list to any radiator shop and they will know what to do if your not a do-it-yourselfer.

The bottom line....This conversion will cost you about $350 to $400, about the same as replacing the origional components, but with the benifit of no more problems and the insurance of not overheating and causing expensive engine damage.
Happy Jeepin' "

Well, that conversion should be helpfull. But how do you purge the air from the top of the block?

The Coleish1
"Without Crew Chiefs Pilots are just pedestrians with cool sunglasses."

This may be a little difficult to do but it works 1st time and there is no need to purge, purge, purge....

The way I do it is this:

1: Remove your thermostat and drill a 1/8" hole in it as close to the center of the flat ring as is reasonable. Then re-install it with the hole to the top of the thermostat. This will allow air to escape even though the thermostat is closed, and will not affect the workings of it at all.

2: I cut the heater hose that goes fron the top of the water pump to the heater box radiator about half way between the water pump and return hose into the pressure bottle. I use a 3" long piece of 1/2" copper pipe to reconnect this hose when I'm done. (Don't forget the hose clamps)

3: Now fill the block with anti-freeze through the pessure bottle till it is just about to come out of the hose you cut in two. Do not be affraid to over fill the system because the expansion bottle has a little bubble on the top that prevents this. Once the system is full, put the cap back on the bottle. Set the two ends of the cut hose up in such a way that they don't empty out the anti-freeze. (Makes a mess.)

4: Now I lift the nose of my jeep about 2-3 feet in the air. I accomplish this by using a mechanics jack placed under the front differential, and jacking as high as I can. (Please use jack stands under the axle for safety.)

5: Once the nose is way up in the air, I turn both ends of the heater hose upwards so that these are now the highest point of the cooling system. Including the front radiator that is way in the air with the nose jacked up.

4: Now you can use a funnel to fill the rest of the system. I found that if I fill the rearmost end of the cut heater hose and look for spilling on the front side of the cut hose it works best. (This allows the air to come out of the thermostat side of the hose, which is the front piece of the hose you cut in two.) If you have done this properly, then the expansion bottle should be full, (allowing for the little bit of air that was trapped by the bubble, as it sould have been,) and the two ends of the heater hose should also be full. Reconnect the two ends together and clamp them and you are done.

5: Start the engine and watch you cooling system working like a charm. (Until next time.) No purging needed, no anti-freeze wasted.

Just a word to the wise, keep an eye on the air level in you expansion tank, never let it take up more than half the bottle. Better to keep filling it regularly than to have to go through this whole proccess again.

I am looking into buying a 1992 Jeep Cherokee. The body is perfect, The interior is perfect, Engine is a VERY strong straight six 4.0. It has a new computer, new water pump, new fuel pump, six disc cd changer, and a pretty sweet sound system. The guy I am buying it from is an electrician, but doesn't know a whole lot about engines. He has done all the work himself including a thermostat swap. The asking price is 750$. It has about 126K miles. The problem is that the coolant intermitantly overflows and then the jeep overheats. I havn't had a chance to troubleshoot it, and I know that the thermostat is easily installed wrong. I guess my question is, is it worth buying, and what could the random overheating be? Thanks for the help.

The Coleish 1
"without crew chiefs, pilots are just pedestrians with cool sunglasses"

If everything else looks good, I would check the radiator. They have a tendancy to clog and stop cooling.

I cannot tell you for sure what can cause YOUR random overheating problem but I can tell you that for mine it was caused by the cooling system "swallowing" air. (This I found out by trial and error and many many gallons of anti-freeze!)

Apparently the older cooling system, (read sealed cooling system,) cannot purge itself of air and so everytime it sucks a bit of air into the block it stays there until the air pocket is sufficiently large enough to prevent cooling in that area. Once this happens steam builds up and pushes the coolant even farther away which causes it to heat even further. Since the air cannot escape because of the design :screwy: , the problem compounds quickly and overheating occurs spitting the anti-freeze all over the ground.

Drilling the thermostat as I have described before helps alot as it helps to evacuate the air when the engine is not running and the thermostat closes, but this is not the ultimate fix. Which is to change the system over to the newer cooling system, (read open cooling system).

I have also found that parking for a few minutes with the nose facing up on a hill , (the steeper the better, loading docks work good for this or dirt mounds etc.), every once in a while also helps to evacuate trapped air, (best to have a drilled thermostat and engine turned off.)

As far as you wondering if you ought to buy the beast, all I can say is that mine is an "89 with over 330,000 km (180,000 mi), and all the original equipment is still there and working fine except the ABS brakes which I changed over to non ABS because I was having problems with it. This also is an easy enough fix.

If you ask me if it is worth buying it I would say yes. Even if you decide later it's more than you bargained for and decide to let it go, it sells quickly.

Hope this has helped you.

I have a 92 XJ and it started running very hot all of the sudden. The radiator was starting to clog up. Autozone sells an exact replacement for about $130. I installed it in about 1 to 2 hours and I have never had a problem since!

All good info. It sounds like I am going to have some real fun working on this jeep. I'm looking foward to setting my bronco on fire and pushing it off a cliff and getting started on the XJ. I'm going to buy it and register it wednesday. I'm taking 2 days away from work to tear the whole thing apart, fix it and put it back together. Taxes come back friday, and I think with 4500$ I might be able to do alot of fun stuff with this jeep. I'll post pics when I get it, and about a week later to show off the skyjacker 4 1/2" lift thats going on very quickly. Thanks for all the insight on the cooling system. I feel like I have a VERY good understanding of how the whole thing works now.

"without crew chiefs pilots are just pedestrians with cool sunglasses."

If I'm not mistaken the 92 Cherokee radiator is the "open circuit" type. (With the radiator cap on the radiator.) If this is the case then you would not have any of the problems that are faced with the 91 and previous models, that of air pockets and unexplainable overheating.