Pre 92 Cherokee Radiator Conversion

[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'

[Benita B. Ballif]

WOW! Thanks sooooo much for the detailed advice. You have just saved my Jeep from being taken out behind the barn and me shooting it to put it and myself out of our misery. I'll let you know if it works.

[BCBlues]

Your Welcome.

I'm a general mechanic and the Jeep was driving me crazy. (I'm supposed to know how to fix things) I combed the wrecking yards to see what I could find on the various years. Thats how I came up with the conversion.

If you don't want to use the thermostat housing and wire the relay to the new style switch you can get the switch housing that Chrysler used on the 92 Jeep. Its expensive, and I don't like it. It splices into the lower radiator hose and uses your original switch so you don't have to do the wiring mod. The reason's I dont like it 1. Its one more place for a hose to leak from, 2. the stock switch turns on at 230 degres and that is right on the edge of doom for the jeep motor.

I have about 5000 miles on my conversion. The jeep is my wifes. She is constantly in stop and go traffic on her commute. We live in the mountains of CA so the commute includes long trips up steep grades on her return. The jeep has not lost one drop of coolant since the conversion. The temperture gauge never moves. It works great with full passenger and luggage load. I also changed the thermostat, water pump, and fan clutch at the same time as I did the conversion.

Before the conversion the dam thing was always boiling coolant out of that stupid expansion tank and the coolant ruened the starter motor and made a mess of the wireing under the tank. She used to carry two gallons of coolant with her every where she went.

The wife drives easy, I drive hard. It doesn't matter how it's driven the temp guage never moves, and stays just below the middle of the guage.

My AC doesn't work so when I get that fixed I'll update the post after I see how it goes.

BC

PS.... Dont forget to drain the coolant from the engine block. The drain is a torex plug just behind the exhaust down pipe on the driver side of the engine block. Use 1.5 gallons of coolant and 1.5 gallons of distilled water for a 50/50 mix (capicity = 3 gal). Use distilled water to prevent future corrosion from mineral deposits and other nasty stuff that clogs things up.

[mrtoadie]

I just bought an '88 Cherokee off a guy for $25 because he said he was sick of it overheating and no matter how many times he "replaced the radiator" it would still overheat. Thanks to you, I think I can solve that problem. Now I just need to get rid of the smell...

[BCBlues]

As promised heres an update to the conversion.
I fixed the Air conditioning and the coolant temp on the stock guage only goes up a tiny bit and that is when pulling a steep grade. All other times it stays where it has been, just under the center mark. So far so good.

[invisiongrafix]

Is this conversion only for the ease of filling the system? I met a guy yesterday that spliced a radiator neck (a "T" with the neck for a 13 lb. cap) into his upper radiator hose on his 87 Cherokee. He fills through the new cap and has no problems.

[email protected]

[Saudade]

Well the benefits are:
1. Easier mantenance
2. Better coolant recovery (actually, there's none with the closed system)
3. Better cooling especially if you use a 3 core radiator.

However, I have an '88 with the orginal system. I have a new stock radiator (old one leaked), new electric fan switch and new thermostat. Once I properly filled the system (no trapped air) and replaced the expansion bottle's cap (last Spring), I have no trouble with the cooling system. Normal driving keeps the temp well below the 210 mark. Driving in slow traffic or long periods of idling cause the elec fan to kick in regularly around 210-220. I have yet to overheat it despite the usual traffic and warm weather here in the greater Los Angeles area.

[invisiongrafix]

Can this same thing be accomplished using the inline fill neck from a Dakota or Durango 4.7?

[89ltd]

sound like a nice modification, I've book marked for next summer, I did away with the shitty abs system, may as well change the cooling sytem as well....

[invisiongrafix]

The NAPA radiator for the '92 is a two row, isn't it?