UPDATE: Thanks to Bigoffroad.com and Troy Morris. Troy figured a way to use the HO temp switch to operate the closed system fan automatically. Check out this link for more info GREAT TIP. THANKS!!

Older Cherokee's with 4.0 liter engines ('87-'91) have the factory closed radiator system that can be less then useful or easy to maintain. It's often a hassle to fill the radiator and the plastic pressure bottle constantly develops leaks. I decided when my radiator sprung a leak that it was time to convert to an open radiator system like the '92+ Cherokees have (radiator with a cap, no pressure bottle). This was virtually a drop in swap and this article will explain the in's and out's of doing the conversion.

History: This new system is going into a 1988 XJ with 4.0 ltr. engine.

(Note: All new parts for this conversion are for a 1992 Cherokee or newer)

To start out I called Radiators Direct Inc., a reputable mail-order radiator distributor, to see what my options were for a new radiator. I really wanted a 3-row radiator so that I could attempt to eliminate any future cooling problems. When I asked for a 3 row all metal radiator for a 1992 Cherokee the salesperson told me that the only company that offered one was GDI. He also told me that Modine offered a 2 row but I really wanted to get a 3 row so I chose the GDI radiator. For just under $200 the radiator arrived at my door within a few days.

Now that I have the radiator squared away I needed a few more parts. I called up Leon Rosser Jeep/Eagle to get some factory parts. Since this open radiator system needs an overflow bottle I decided to order the factory bottle and the cap to go with it. You can buy a generic overflow bottle at most auto parts stores but I found that the factory bottle fit well. The heater valve in the older XJ's allows some hot water to always pass through the heater core thus making your A/C have to work that much harder. The newer heater valves close off the heater core entirely when the heat is not on, not allowing any water into it. My local parts store could not get it so I also ordered the valve from Leon Rosser. Although it is not entirely necessary to replace the heater valve it is recommended that when you swap the radiator to the open system you also purchase the new heater valve. The old one could be used but the hose configuration on the old valve must be altered to fit with the new system. Other parts needed for this conversion were approx. 6' of 5/8" heater hose (bulk roll is fine or you could buy the factory pre-molded hoses), approx. 7' of 1/4" rubber hose (I got fuel line. It worked perfectly), and last but not least, a new radiator cap to top it all off.

To start the swap I decided I would buy some radiator system flush and flush the entire system before I pulled the old radiator. After completing this I drained the radiator. I used the drain on the passenger side of the radiator but you could just as easily pull the lower radiator hose off to drain the fluid. Opening the drain makes it easier to collect the old anti-freeze. While it is draining remove the Aux. Electric fan, unbolt the mechanical fan shroud and unbolt the metal cover plate that is on top of the radiator. After pulling the cover, disconnect the upper and lower radiator hoses and the 2 transmission cooler lines (only for Automatic transmissions). Next remove the straps on top of the radiator that connects the radiator to the A/C condenser. Then with everything disconnected the radiator should lift right out.

If you have an automatic transmission install the cooler line fittings that are supplied with the radiator. Using Teflon Tape (used in plumbing) on the threads of the fittings will ensure that the fluid does not leak. The new radiator should drop right in. Install all the removed lines, hoses, and brackets that were removed. Go ahead and reinstall the metal cover plate at this time too.

If you are not changing the heater valve you MUST alter the hoses so that water only flows from the thermostat housing to the heater core and back. With the old style it had junctions that would push anti-freeze through the pressure bottle. Since the pressure bottle will no longer be used the lines need plugged and spliced so that the coolant flows in the right direction. The new valve is only $20 so it's definately worth replacing.

Since I was replacing all of the heater hoses and the heater valve I removed all of the old hoses connected to the old pressure bottle, heater core, the heater hose connected to the thermostat housing and disconnected the vacuum line connected to the valve. While I was at it, and to get better access to the hoses connected to the heater core, I removed the pressure bottle and the metal shelf that it sat in as they will no longer be needed. I cut a piece of the bulk heater hose to approx. length that would place the heater valve in a similar location to where it was stock, measuring from the thermostat housing to the approx. location of the valve. Then I installed the hose onto the thermostat housing and also installed the valve. Then I cut the 2 pieces of hose to connect the valve to the heater core. Since I already have a "flush-n-fill" connector in the hose from the heater valve to the water pump and did not feel like taking the thermostat housing off to get to the hose I just spliced a new section of hose from the valve to the "flush-n-fill" connector. If you have the thermostat housing off and can access the water pump there is a small piece of pipe that the heater hose connects to. In the pre-'92 models it's a short straight piece that makes it very difficult to access. However there is a new piece that is longer and elbow shaped that brings the connection to a more accessible location above the thermostat housing. I did not use this because I didn't want to take it all apart to change the pipe. The valve diagram is shown in the diagram below.

Now that the hoses and heater valve are in place now it's time to install the overflow bottle. I placed the overflow bottle in the hole where the old pressure bottle used to be located. I was going to make a bracket to enable me to be able to fasten the bottle down but as of now after a couple of trails and hundreds of miles the bottle hasn't moved. It's rather tight in there and the hood holds it down in. Take the fuel line and connect it to the nipple on the neck of the radiator. I then ran it along behind the fan shrouds around the battery between the battery and fender then along the fender up to the overflow bottle. I zip tied it in a couple of locations behind the fan shroud to ensure that it wouldn't move.

With all the hoses tight and in place, fill the radiator with proper proportions of anit-freeze and water. I have been using with good success Havoline Dex-Cool anti-freeze. The new anti-freeze is silicate free which will decrease the amount of deposits that accumulate on the inside of radiator. In addition, this stuff has a 5yr. 150,000-mile life span. The Dex-Cool is orange in color. Havoline recommends mixing approx. 70% anti-freeze to 30% water. Fill the radiator as much as possible and then fill the overflow bottle up to the max mark. Put the new radiator cap on. If there are any visible leaks now is the time to fix them. Start the engine and allow it to heat up enough to open the thermostat. Also turn the heat on so that the heater valve will open pushing the new fluid in. I recommend continually checking the fluid level for the first few weeks to make sure that fluid is coming and going from the overflow bottle.

In the '92+ Cherokee's the Electric Fan temp sensor is in the thermostat housing. I'm still not sure if the newer thermostat housing will fit older Cherokees. There is a part that is offered by Mopar that is a splice in the lower radiator hose that allows use of the old Temp sensor, but this part is rather expensive in comparison with the other parts of the upgrade. I didn't use this either. I already had wired the electric fan to a switch on the dash so I will just use the switch manually if I see the temp is getting high. Stay tuned to Cherokee America to see if I ever find out if the newer thermostat housings fit the older XJ's.

Because the parts in my truck were getting old the old pressure bottle was leaking, the heater valve was developing a small leak and when the radiator leaked, that was the last straw. I did this conversion for the same price, if not a little less then I would have had to pay to replace all the old style parts. Now being over a month since the swap I have not had one bit of trouble with this system. It's easy as ever to check, easy to fill, and most of all....brand new.

Before any parts removed	After conversion completed
Old Radiator in	New radiator in
New heater valve and hoses