For a little over $200 total (parts), you can ditch your troublesome "Closed" system for good.
A later style XJ radiator introduced in 1991 will bolt right in with very little re-plumbing, and provide a far more trouble free cooling system. There are a couple of manufactures that offer a heavy duty (2 row core, or larger capacity 3 row core) replacement radiator with a filler neck with conventional cap (kill two bad birds with one stone). I chose the GDI (Go-Dan Industries) radiator for my conversion because they make a high quality product and have a great reputation.1991 was actually the changeover year, but there can be a little confusion when ordering cooling system parts since there was a lag in updating some parts manuals. For this reason the new style cooling system is commonly referred to as 1992 and later. I also recommend that when ordering parts you order them for a 1992 model. Radiators Direct and Duracore both sell the GDI (Go-Dan Industries) 3 row radiators, and will ship them to your door for $180~$200 including shipping. You can e-mail them both for a quote, giving them the info on your model, and requesting a GDI 3-row replacement w/filler neck (I found Duracore to be about $20 cheaper for the same radiator). It will work with either transmission and has the studs for the A/C condenser mounting brackets. It is truly a drop in replacement for the old 1 or 2-row closed radiator.
This upgrade will eliminate the troublesome plastic pressure bottle and the associated hoses that divert the coolant to it. For this reason you will need to order a '92 heater control valve since you will be eliminating the "T" junction that is part of the old heater valve. It is possible to plug the unused outlet from this "T", however this could become a weak point in the system and cause trouble later. The new heater valve is only around $20 and will simplify the conversion. You will also need a coolant recovery bottle, which can be placed in the same location as the pressure bottle after it and its platform are removed. This is where the factory mounts it in the post '91 models. If you have installed a K&N/air tube conversion, you can mount it in the opening left by the Air Box which is much closer to the radiator. This can be any good aftermarket bottle, or you can order a stock '92 & newer bottle from the dealer (or Leon Rosser) if you want to stick to all Jeep parts. I also strongly recommend buying three of the four heater hoses for a '92. Although you can use regular bulk hose, it is difficult to adapt the upper heater core hose to the valve due to the fact that the nipple on the heater core is 3/4" and the one on the valve is 5/8". The factory hoses will really make pluming the new valve a breeze and the end result will have a neat and tidy factory installed appearance.
There is one caveat with using the '92 radiator. It does not have the provision for mounting the temperature sensor for the electric auxiliary cooling fan on the side of the tank like the earlier model has. In '91 the sensor was changed and relocated to the thermostat housing. There are two ways around this minor problem. You can purchase an adapter that is spliced into your lower radiator hose and accepts your current sensor. Or you can install a manual switch that turns the fan relay on as desired. Since I had previously installed a manual override switch for the auxiliary cooling fan, I chose to eliminate the sensor altogether. I found that it never came on until it was too late anyway, so I didn't bother spending any more time and money adapting it back into the system.
Installation of these items is straightforward and easy. All the later model parts are direct replacements with the exception of the heater valve which has a different configuration. If you use the factory heater hoses in your conversion this will pose no problem and everything will fit into place perfectly. There is an arrow imprinted on the body of the valve housing indicating the direction of flow. Refer to the diagram for the proper orientation of the valve and the various hose connections.
You will note in the parts list below that I have listed both a '90 heater hose and a '92 heater hose that runs from the heater valve to the water pump. This is because the formed shape of the hoses don't allow for easy interchangability between the years. So what you will need to do is connect the late model hose to the heater valve and the early model hose to the water pump. Then find a spot in the middle along the top where they lay beside each other and cut both hoses. Install a cooling system flushing-adapter as a splice to join the two hoses together. This not only serves as a splice, but also a convenient place to bleed air from the system. Hook up the vacuum hose that operated the old valve to the new valve and everything should operate as before. If you need some more guidance through the swap, feel free to e-mail me for details, or look at Bob Mock's article on the Pre '92 Radiator Conversion that is posted on the Cherokee America site. He has a well written article on the swap with lots of photos. however I think there might be some discrepancies with his part numbers (not sure), so better double check when ordering the parts. I have verified the heater valve part number above through the dealer, and it is correct. The important thing to remember when ordering your parts (now or in the future), as far as any parts clerk is concerned, you are buying parts for a '92 4.0 cooling system. Don't let any salesperson tell you the '92 parts won't fit your year, they are direct replacements with no modifications necessary.
Parts List:
* GDI 3-row Radiator with a filler neck: 43-2335
'92 Heater control valve, 4 port: 56005900
'92 Heater hose, T-stat to heater valve: 56004783
'92 Heater hose, heater valve to core: 55036941
'92 Heater hose, core to heater valve: 55036942
'90 Heater hose, heater valve to water pump: 52003878
'92 Heater hose, heater valve to water pump: ________
Aftermarket Cooling System Flushing-Adapter
* Optional temp sensor adapter: 83505113
(splice into lower radiator hose)
Available from Leon Rosser* Denotes parts not available through the dealer. All other
parts are available through your local Jeep dealer.
These part numbers are courtesy of (and were verified by)
Rick Hangartner, Parts Manager at Port Angeles Jeep/Eagle/Honda.
Back to the Care and feeding of the
early "Closed" Cooling System