My XJ is down... I need some quick advice/support with 88' Renix closed system

Well...I haven't been here in forever it seems. My XJ has been running great until the past 6-8 months. Two coolant bottles later, I'm reconsidering my closed system setup. I'm now homeschooling my children, so maintenance time is very limited for me. I have searched and reviewed alot of threads on the swap. I've also noticed that Mac's has an aluminum Surge tank as a replacement.

1. Is there a "current" thread on the Closed to Open conversion? My search returned threads from '09. I thought someone might have a more Up-To-Date link with newer options??

2. Is there a Kit as such that I can buy to speed up my conversion? For me...having everything together really helps me out these days.

3. I am taking my radiator to have it flushed out...it is an all metal unit from 12 years ago when Clemson 4Wheel Ctr. installed my Jasper 4.0L. If it leaks...is it advisable to buy a 3-core or stay with the 2-core?

4. IF my radiator is in fact good...I may just buy the Mac's Surge tank and see how it behaves. Any feedback on their alum. Surge tank?

If you care to take the time to offer up your suggestions, I would be grateful. I'm down now with no "work" Jeep. After I make a decision on what to do to keep the coolant in the engine, and not on the driveway, ...I'll hit ya'll up for advice on another problem! Lets just say it may involve one or more of the following...TPS, IAS, CPS,... Seems like it might be more economical to buy a newer XJ sometimes...

Thanks for your help!

Jeff C.

Has the radiator been replaced? What's the mileage on it?

Per Jeep wrenches I've talked to, the OEM RENIX radiator seems to run 150-180Kmiles before it starts to clog up, no-one really knows why (this is even with regular maintenance!)

Even though the OEM radiators were Modine, there's still a difference between the OEM Modine and aftermarket Modine (it seems.)

I've put an aftermarket Modine in to replace the OEM radiator in several RENIX rigs, and haven't had a problem at all with them in over 200Kmiles. Each!

The CSF radiators offered by DPG Offroad (a sponsor here) have also garnered uniformly excellent reports from the field; if I couldn't get Modines for a good price, I'd get CSFs from Dirk (the CSF is also an all-metal unit.)

People who do the "closed-to-open" conversion on RENIX usually end up inadvertently fixing the essential problem in the first place - the clogging radiator. Conversion requires replacing the radiator - just as replacing the radiator outright with a direct-replacement unit. And, a direct replacement is less work.

As far as the pressure bottle, I'll usually replace it every five years out of hand, until I get around to fabbing something up (the unit from Mac's Radiator is a bit spendier than I can afford to go.) Replacements - with cap! - can be had for a reasonable price from Morris 4x4 Center - when I've got a few bucks ahead, I'll order a couple just to stay ahead of the system.

Believe it or not the dorman bottle I got from autozone is actually a very nice one. It's thick as hell and the cap feels tight when u put it on. I tried a few other bottles and they just wouldn't hold the pressure. And new radiator and the coolant bottle worked for me. Also running a trans cooler and taking it out of the radiator loop helped tremendously with cooling issues for me.

I converted my '88 and it is really a simple conversion.

I kept the radiator -just flushed it out, as I had no over heating problems. Got hold of a Toyota MR2 inlet and spliced it into the top hose. Took out that stupid closed system coolant bottle and replaced it with a normal open system bottle with a piece of rubber hose connecting it to the MR2 inlet. Also bought a new radiator cap for it -16psi I think.

The reason I did the conversion was I had no real confidence in the system, especially since I drive from lLondon to Poland each summer. I never had a problem with the closed-system, just, it wasn't a matter of "if" it would fail but "when" - being stuck in the middle of a foreign country is just too much adventure for me!

Others have spoken highly of the closed-system but it isn't for me.

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1988 Cherokee 4WD Auto 4.0litre

I've gone through your situation as well in my 1990 XJ. I got the Mac's surge tank and have been using it for the last couple of months and am pleased with its operation. I recommend. Of course, I also ended up replacing my rad, fan clutch, hoses, thermostat and water pump. Solid as a rock now!

If you do the open conversion (I only did mine because I needed a new radiator and an open style one was given to me for free) You'll need
Radiator
91 heater valve (if you choose to keep it, I deleted mine.)
and a catch bottle.

There's one at autozone in the generic cooling parts, it's a slimline bottle that fits nicely in the drivers side fender, just in front of the airbox. Costs about $10.

that's about it for parts. You'll have some interference between the airbox and the filler neck on the open radiator. and you may have to trim the core support for the neck as well.

Not a big deal, I did my entire cooling system in an evening(hoses, pump, t-stat and housing,fan clutch and radiator), You might as well plan on doing the fan clutch and water pump, because you'll have the radiator out and it's just a good time to do it while you've got easy access to all of it, vs. trying to do that stuff with 4" of space to work in.

Thanks for all the replys. I have ordered the '88 3row HD CSF radiator, Moroso 1.25" x1.25" in-line filler neck, plus I'm replacing every cooling component/part to ensure a free flowing system. I'm also re-doing my AC system while I have it down. I'll start a thread with pics documenting all that I've done to resurrect this Renix system. Let me get it finished, and I'll get started on the new thread...

One thing about it...when you take the time to refurbish a "system" like this, you really get to know each component and better understand how it all has to work together. AND...you find other problems too...like a missing motor mount nut!!!

Stay tuned...

SuperRoo said:

I converted my '88 and it is really a simple conversion.

I kept the radiator -just flushed it out, as I had no over heating problems. Got hold of a Toyota MR2 inlet and spliced it into the top hose. Took out that stupid closed system coolant bottle and replaced it with a normal open system bottle with a piece of rubber hose connecting it to the MR2 inlet. Also bought a new radiator cap for it -16psi I think.

The reason I did the conversion was I had no real confidence in the system, especially since I drive from lLondon to Poland each summer. I never had a problem with the closed-system, just, it wasn't a matter of "if" it would fail but "when" - being stuck in the middle of a foreign country is just too much adventure for me!

Others have spoken highly of the closed-system but it isn't for me

Click to expand...

Forgot to mention, I also deleted the 'heater valve'. I now have my heater hoses running like the later models. Just plug the vacuum line with a screw. I've experienced no difference in heat soaking into the cabin at all, btw. My vents flaps are shutting off the hot air as they were designed to do.
I'm very pleased with this conversion:clap:
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1988 Cherokee Laredo 4WD Auto 4.0litre - originally from California

I plan on doing the open conversion this next upcoming weekend, I'm sick and tired of it sometimes working great holdin at like 185 until it gets a hair up it's butt as soon as I hit the trail it wants to get hot... Im not sure if i want to run my heater hoses direct into the heater core or if I want to bypass it, my renix has 250,000 miles on it so I don't want to deal with a blown out heater core...

Well...my radiator came today...but it was damaged. Called Radiator Barn and they want pics...and they said another one should be on the way tomorrow...and hopefully to me by Fri. I don't understand why CSF doesn't pack these radiators any better than they do. That's a lot of money between two thin pieces of cardboard.

MaxxXJ said:

I plan on doing the open conversion this next upcoming weekend, I'm sick and tired of it sometimes working great holdin at like 185 until it gets a hair up it's butt as soon as I hit the trail it wants to get hot... Im not sure if i want to run my heater hoses direct into the heater core or if I want to bypass it, my renix has 250,000 miles on it so I don't want to deal with a blown out heater core...

Click to expand...

I ran mine straight to the heater core.

there's a barbed splice fitting in the glovebox