MJ Newbie...

I am a long time Jeep guy and have always wanted an MJ. My first car ever was a 1995 YJ, then I moved to a TJ, and shortly after that, bought the love of my life; my 2001 XJ. I am planning to do an engine swap in the XJ soon, so I decided I would pick up an MJ as a parts runner/weekend driver while the XJ is under construction. I picked up a 1989 2WD long bed with the 4.0 and AW4 trans with 135k on the clock for a thousand bucks. It runs and drives fine, but has some over heating issues. So therein lies my question. Do most MJ owners stick with the closed cooling system, or upgrade to a newer open system? I've found a new radiator, upper and lower hoses, and overflow reservoir to retain the closed system on craigs list for 75 bucks, but not sure if i want to invest in that, or put the 75 towards doing the conversion. Any tips or advice would be much appreciated.

i got a new radiator when the neck popped out of mine. new rad has a cap made onto it. i plan on getting a new overflow tank and ditch the oem tank and all that hose garbage. all you *should* need is heater hose and a overflow tank and a new/different radiator. should be an easy fix. dont forget to plumb in the heater hose valve. and take the old junk out and shoot it LOL

Was the radiator you got out of a newer XJ? If so, were all the mounts and size the same?

There is no reason that the closed system shouldn't work, but my philosophy with my MJ was that when the rad went bad, I would swap over to the open cooling system. I would do some searching on here for overheating issues. It could be as simple as the overflow tank having a crack in it, and/or the cap on the overflow tank being bad. That will cause a non-HO closed cooling system to overheat.

Also, not sure if yours has AC, but I swapped a late-model electric fan into mine, and ran it on a switch in the console.

I like that fan on a switch idea

conklinator said:

Was the radiator you got out of a newer XJ? If so, were all the mounts and size the same?

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i told the parts monkey i need a rad for 1989 mj part xyz and he went and got it. turns out it has it's own fill neck. so i plan on for simplicity of the hoses sake, just clean it up and delete any un needed joints and tanks etc.

sandsgg said:

I like that fan on a switch idea

Click to expand...

Works great, especially when rock crawling/offroading. When you snag an elec. fan, snip the wire harness so you have the female side of the plug too. Then its easily removable. You need a higher amp toggle switch too, 20A or better.

A.

I know a lot of people say the stock mechanical fan cools better than electric, but I'm skeptical. What do you guys think about running 2 of these off of a toggle switch?

http://www.quadratec.com/products/51210_7173_07.htm

You can use a rad with a cap on the closed system, just make sure you get a min of a 16lb cap.
I have the DBO e-fan kit and it works great.
I have an 89 renix xj with the stock closed system.

I have reluctantly switched both of my RENIX era XJ and MJ over to the open system. If you need a rad its the right time to do it.

I recommend getting a 96 XJ rad, use the heater hoses and heater control valve from a 96 XJ and then just pick up a cheap over-flow bottle from Oriellys. As for dual stock E-fans, they work great but get the newer style fan with the "S" shaped blades.

My RENIX era XJ;


The MJ

Wow... Your engine is really clean... I am definitely going to update my system. I'm basically just going to copy everything over from my '01 XJ. I was looking at higher end 3 core rads, but then I've heard many people saying that the plain old stock single core radiator is the best bet. Thoughts?

conklinator said:

Was the radiator you got out of a newer XJ? If so, were all the mounts and size the same?

Click to expand...

mine was a advanced auto replacement for hundred

i am in collision repair, and i never could figure out why they call this closed . the design has been around for many years, european cars have had them for a LONG time. i have replaced many rad's and they all are open LOL or we could never fill it ! i like the simplicity of fewer joints and hoses to fail. and the radiator vacuum tool is one of the best tools ever to avoid the air pocket in the motor.

G

Andy in Pa. said:

There is no reason that the closed system shouldn't work, but my philosophy with my MJ was that when the rad went bad, I would swap over to the open cooling system. I would do some searching on here for overheating issues. It could be as simple as the overflow tank having a crack in it, and/or the cap on the overflow tank being bad. That will cause a non-HO closed cooling system to overheat.

Also, not sure if yours has AC, but I swapped a late-model electric fan into mine, and ran it on a switch in the console.

Click to expand...

the closed system works fine, provided it's all new.

the plastic bottles have problems after they're a few years old.

I swapped mine ovr to open simply for parts store availability.
Random parts stores in the middle of nowhere don't have Renix cooling system parts, but they've all got HO radiators.
as for the fan, the stock e fan was on a temp switch in the rad, if you get an HO water neck it will have an extra hole in it and you can wire a new temp switch right into the thermostat housing. There's a factory relay for it, use it.