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New to the MJ world and LOVE IT!!

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I've had a few friends that wheel XJ's and they complain about the early radiator setups. I have an 87 MJ with 4.0 and it has no radiator cap. The radiator has a small leak in it and I'll be needing to change it soon. So, would it be in my best interst to upgrade it to a newer style?

Who has done this mod, and will i benefit alot from it? :idea:

And what year should i get parts from??



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Yes, yes, and yes.


I had an '88MJ with the same cooling system setup as yours and it loved to randomly overheat without warning. Sometimes I could go 10 minutes, sometimes 20, sometimes 5 before the needle on the temperature gauge started straying away from normal temps between 195-210 degrees F. I replaced damn near everything - radiator, water pump, thermostat, expansion bottle, expansion bottle cap with the same results. I "upgraded" to the newer, open style cooling system and the truck hasn't overheated since. I didn't do it the typical way, but here's what you'll want to do:


Grab the radiator, heater core hoses, and heater control valve (if you want, you can even leave this out entirely, but then you'll need to have custom length heater hose made up) from a '91 or newer MJ or XJ with the 4.0L engine.


I opted to go a slightly different route, which may not have been the cheapest, but it was the most practical for me since I had just put a new "closed system" radiator in my '88MJ. I bought a 1.25" universal radiator filler neck and spliced it into the upper radiator hose. I then removed the existing heater core lines, heater valve, and expansion tank. I installed a 11/16" and 5/8" custom length heater core hoses and bypassed the heater valve entirely. I then found a universal overflow tank at Autozone for $10 and installed it where the old expansion tank was. My costs were as follows:


Moroso universal radiator fill neck: $25

16lb. radiator cap: $5

Universal coolant overflow tank: $10

Custom length hoses: $8


Total cost: $48 but round up to about $60 to account for hose clamps and coolant. At local pick'n'pulls, you can usually get the radiator, heater core lines, heater valve, and overflow tank for about $50 or so, but you'll need to drain a bit more coolant than I did with my setup.


Here are some pics of mine:




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I installed a newer radiator with the rad cap and left the rest as-is. works great. :)


I did that on my '90 XJ and had issues with the flow. The Jeep would end up popping the rad cap off the closed system overflow bottle and spew coolant out. When I looked into it, the lines are run slightly different. I think this is only an issue if you keep the heater valve though.

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