My Jeep has had the popular upgrade to the 1991+ open-style cooling system performed to it. Not only was it blessed by the factory with the goofy closed system, it also received a 1-core radiator for good measure. This system was barely adequate in Alberta during summer-I don't know how it would work somewhere where it really gets hot. Here is a list of the part numbers that were used to perform this conversion. Most parts were sourced directly from Chrysler so unless specified the following are all Chrysler part numbers.

The radiator is a direct bolt-in as far as size/mounting goes. To remove your old radiator you must remove the electric fan (if so equipped), the mechanical fan shroud, both rad hoses, the automatic transmission cooler lines (if so equipped), the rad fan sensor wire (if so equipped) and then the plate across the top of the rad (that actually holds it in) can be removed. Once this is out there are 2 screws that hold the A/C evaporator (again if so equipped) to the rad. I would strongly recommend changing both rad hoses while the radiator is out because they are incredibly miserable to access with all components in place! I had changed mine the year before when my harmonic balancer slipped (another story!) so I deemed them suitable to reuse. When you reinstall the rad you will notice that there is no provision in the new radiator for the electric rad fan switch. Chrysler used to supply a coupling that was to be installed in the lower rad hose-basically a sleeve with a port for your switch. I was told that it is no longer supplied and it was fairly pricey. 1991+ have a different thermostat housing with a 3/8"NPT port for a fan switch. If you order the above #'s you will receive the proper housing, a new switch and a 6" harness with the proper Weatherpack plug at the end. You can clip the wires off your old switch and splice them and the new plug together with some extra wire in the middle to let you reach both ends properly. The image below should help you see the difference.

As you can see the new thermostat housing looks (and fits) exactly like the old one with the exception of the port on the driver's side

There has been some question as to whether the 91+ housing was a bolt-on for '90 and back-I can tell you yes it is.

You will have to change your heater valve when you do this swap as well. The '91+ valve will actually help your A/C work better (assuming you have A/C) because it diverts all coolant away from the heater core when closed. You will have to buy some bulk heater hose to plumb it in. Below is a picture of it installed (albeit not a very good picture!):

With the valve oriented as shown in the picture (left side is towards the firewall) the lower line on the right goes to the thermostat housing, the upper line on the right goes to the water pump, the lower line on the left goes to the upper heater core fitting and the center line on the left goes to the lower heater core fitting. (Sorry I know it is kind of confusing but I never actually thought about taking pictures until after everything was installed, but judging from my photographic expertise more pictures would not necessarily be better!)

I mounted the coolant recovery bottle where the old pressure tank and its bracket were mounted. Mine is temporarily wired in place now as I am not real happy with the way it fits in. I think a trip to the wreckers is again in order to find a more suitable donor-when I settle on the final candidate I will amend this article suitably. Below is a picture of the bottle in place:

I ran the overflow line above the top of the fan shrouds, securing it to the electric fan with an Adel clamp, around behind the battery and along the RH inner fender to the bottle (you can see it snaking around entering the photo from the bottom left corner). Also see the photo below.

overall impressions

So was the final result worth it? A resounding YES! With the pathetic single-core excuse for a radiator it always ran warm-close to or over 100C (212F) on a hot day. The day I made the swap was fairly warm and I dropped down to 90C (195F) immediately after install. As an added bonus if you do have trouble somewhere this style cooling system is much easier to refill-every time I serviced my closed system it seemed to take 2 days to burp out all the air. There are 3 core radiators available but they were not accessible to me and seeing as I will never tow anything larger than a snowmobile trailer with the XJ I chose to use the 2-row.

If you have any other questions please feel free to e-mail me.