Ughh! Converting to the open cooling system

Well as much as I hate to do it, I think I'm gonna do it. I thought I had my 1990's cooling system flawless after 5-90 showed me the trick of drilling the holes at 12 and 6 in the thermostat. Today I noticed coolant leaking and sure enough after I just replaced all my heater hose plumbing with the expensive moulded ones, my coolant bottle cracked, AGAIN. I just put on a reinforced one like a year ago and its already cracked. So...I've read like 4 write ups(because I'm a good boy and searched) but I never really got too clear of an answer on this one thing. What do you do about the electric fan? I know if you order one of the GDI ones now they have the hole so you can adapt the sensor in but if I decide to go with something besides GDI can I just upgrade to the newer style T-Stat housing and redo the sensor into that? Will the threads be the same and will it reach far enough into the hole to read the temp? It looked like on this article...
http://jeepsunlimited.com/xj/cooling/cool.htm
he talked about plumbing it in but I wasn't sure I understood it right. Can anyone clarify this for me?
Thanks guys,
Collin

Dunno - I still run closed systems on my four.

I do make a point of changing the "football" every five years, and you can get them cheaply from Morris 4x4 Center (>$25 w/cap.) I also sign and date the thing on the front, so I know when I changed it. Haven't had one fail yet.

It's worth noting that the OEMR radiators (on XJ's, and probably Jeeps in general) are good for 150-180Kmiles, then want changing - this straight form Jeep service techs at the local. Get a Modine or a Performance Radiator replacement, and you should be just fine (I think I've got about 100K on my Modine in my 87, then I transferred it to my 88 and I've put another 30-40Kmiles on it - the Modine in my 89 Limited is still steaming along with about 60Kmiles on it. Biennial flushes and coolant replacements - with the use of RO filtered water in the coolant cut. Once I've refreshed the system, the only flush agent I use is cider vinegar - which is a mild acid and breaks up any scale nicely. Complete by running the water through the system backwards to rinse, then drain and refill. Works like a champ - hot vinegar cuts scale and crud just fine, and neutralises easily.

5-90

the answer is yes but you gotta get like something like a 1970 chevy fan switch , the non renix models use a sensor for there not a switch....

5-90 said:

Dunno - I still run closed systems on my four.

I do make a point of changing the "football" every five years, and you can get them cheaply from Morris 4x4 Center (>$25 w/cap.) I also sign and date the thing on the front, so I know when I changed it. Haven't had one fail yet.

It's worth noting that the OEMR radiators (on XJ's, and probably Jeeps in general) are good for 150-180Kmiles, then want changing - this straight form Jeep service techs at the local. Get a Modine or a Performance Radiator replacement, and you should be just fine (I think I've got about 100K on my Modine in my 87, then I transferred it to my 88 and I've put another 30-40Kmiles on it - the Modine in my 89 Limited is still steaming along with about 60Kmiles on it. Biennial flushes and coolant replacements - with the use of RO filtered water in the coolant cut. Once I've refreshed the system, the only flush agent I use is cider vinegar - which is a mild acid and breaks up any scale nicely. Complete by running the water through the system backwards to rinse, then drain and refill. Works like a champ - hot vinegar cuts scale and crud just fine, and neutralises easily.

5-90

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I know, and if I wasn't so finicky I might just replace the bottle again but like I said it has been under a year and this was supposed to be one of the "reinforced" ones too! Pssh. Also, I like the "cleaned up" look of the HO cooling system. I guess I should go with a quality radiator when I do it rather than just the parts store's house brand, you think Modine is as good as any 5-90, you had any experience with GDI ones? Anyone else have any opinions on this?

I've long used Modine (Canada,) with Performance Radiator (Thailand) a close second. I've gotten mixed "reports from the field" on GDI - enough so that I'm not real sanguine about using them.

Considering there's cases where the OEMR units last over 10 years (and I'm changing them after half that,) and the units I've gotten from Morris are just like the ones I took out - only new - I don't see any reason to change anything just yet.

However, if you convert (I still don't see why - just be judicous in your purchase of parts. If the closed system is so bad, why is it gaining prominence in OEM?) you'll want to make sure to get a later thermostat housing as well, then use the Chevvy fan switch, which will go into the thermostat housing.

You'll also need to cut the upper crossmember to make space for the fill neck, and you'll probably need to delete the "T" fittings back near the heater control valve. And, add an overflow bottle somewhere that it will fit - since it's not a pressure line anymore. Just seems like a lot of work to me - I can do less to refresh the closed system, and keep running for less (but that's just me.)

5-90

This site does a step by step...
I did the swap bout 3 yrs ago...wired the aux fan direct and put a switch on ti so I could turn it on as needed...haven't had any probs other than a tstat replacement
http://www.off-road.com/jeep/cherokee/jeepcher.htm

churky89 said:

This site does a step by step...
I did the swap bout 3 yrs ago...wired the aux fan direct and put a switch on ti so I could turn it on as needed...haven't had any probs other than a tstat replacement
http://www.off-road.com/jeep/cherokee/jeepcher.htm

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I put the fan on a toggle switch as well. There is a write-up somewhere that mentions someone finally finding a switch (another make/model) that will thread into the t-stat housing and will function properly. I haven't verified this yet.

I did the conversion and installed a GDI awhile ago. No problems at all with that brand radiator.

My question: So, is there really a place on the 91+ GDI radiators like mine that will accept the old temp sensor? Is it a matter of unscrewing a unused plug? Haven't looked at mine in awhile and so not sure if there were plugs on there.

I still run a closed system. I dumped the factory bottle in favor of an aluminum racing surge tank by Moroso. Mine came from a local speed shop, but Summit Racing now sells them for a good bit less than what I paid.

Just to throw a couple of thoughts out there. The cap on the surge tank has a spring loaded pressure release, usually around 15-16 PSI. The surge tank does a whole lot of expanding and contracting anyway, if the vent in the cap gets plugged, something is bound to give.
My third surge tank in two years (also third cap), started growing cracks (my parts resources/outlets/concessionaires are limited here). I found a .8 bar cap that fit (kind of, threads aren't exactly the same, but it closes, stays closed and seals) or approximately 11 PSI. Cracks haven't gotten any bigger and it still doesn't leak. I've lowered my boiling point something like 9 F degrees form 268 to 257 (with a 50/50 coolant mix), by reducing the pressure 5 PSI. I use rain water or distilled water to fill the radiator, far fewer suspended solids to block the cap vent and coat the insides of the cooling system.
Another thought to keep in mind, for the summer. The lower the coolant water ratio, the better the system exchanges heat. But at the same time lowers the boiling point. With a 15 PSI cap and a 33%, mix boiling point is 257F, with a 11 PSI cap 250 F. I don't have any overheating problems, but if I lived in the desert, I'd be tempted to try lowering the coolant mix to 33% and see what happens.
I'm tempted to switch over to a metal tank, but I'd be unable to see the coolant level in the tank and would reduce my chances of picking up a leak or seep early.
The surge tank, does seem to be the weak point in the system, heat, pressure, expansion and contraction and hardening of the plastics (nylon? Rayon?), seems to make them fail often. I think I'm gonna check out a 240 Volvo bottle and see how it lasts.

One more thing.
Before you do anything, have your cooling system sniffed. I have seen high pressure head gasket leaks cause bottle failure.
Closed systems are not the problem and changing to the old open system will not cure a problem.
All new cars are closed and liquid cooled bikes, atv, and snowmobils always have been.

Collin when I did the conversion on my 88 I changed to the new T-Stat housing at that time. The 88's radiator sensor was to big to fit in to the housing I had make a wire adaptor and use a 91+ sensor. I cant find the schematic I used to convert because the 91+ was different in some way, the RENIX being a switch inside and the 91+ just a element and you need to add a switching component, I cant remember off the top of my head on this. The fast and easy is to wire a switch but I didn't want to do that I wanted the functionality of the original fan system. I'll look around for the schematic (or the article) I used and see if I can post it.

Instead of going to the expense of changing over to a completely open system, try this if expense and time are considerations.
Go to the local U-pull-it yard and look for the bottle on a late model (92-96) Chrysler mid-size auto. The bottle in these cars is shaped differently, but it has a REAL radiator cap, and is made of considerably heavier material.
It will be located in the same place on the cars as it is in your jeep....it is a piece of cake to plumb it in, get the hoses with it and only one of them will need to be adapted...

First of all I did not read the entire thread...

Anyway, down to business... DO NOT BUY GDI, DO NOT BUY GDI. Not to be a trash talker here but I got a bum radiator from them and have heard of too many others with the same story.

I went open a few years ago becuase I felt more comfortable with a conventional cooling system. As may have been noted the sensor on the HO thermostat housing
is just that, a sensor. You will need to get a thermostatic switch to go in it's place. I cannot point you to what exact switch to get as I have not done that yet (I run in bypass mode).

I wouldn't bother going to dual electric fans, everybody that I've known who's done it ended up going back to electric and mechanical because it just works best.

When you do the change do the heater control valve (probably in that write-up), any coolant recovery bottle (I used a Mopar HO Jeep one), plenty of curse words, and a new fan clutch if you haven't recently replaced it. It's a lot easier to do this with the radiator out.

I can't think if there are any other precautions I can tell you, it's been a long night... I'm sure somebody else will cover for me if I goofed it though

Sequoia

5-90 said:

I've long used Modine (Canada,) with Performance Radiator (Thailand) a close second. I've gotten mixed "reports from the field" on GDI - enough so that I'm not real sanguine about using them.

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Between what you and GSequoia said I think I'll go Modine as opposed to GDI.

5-90 said:

You'll also need to cut the upper crossmember to make space for the fill neck.

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I didn't think I would have to, it looks like there's room to clear it? Anyone who has done this know for sure?

Thanks a lot to all you guys for the opinions etc., I was about to just tear into it but I'm glad I'm picking up some info first.

I did not have to cut my '89.

I converted to open system when I swapped motors.
I had a head gasket pressure leak into my coolant that kept blowing bottles/caps. After I upgraded bottles it started blowing hoses apart.

I used the stock sensor I removed from the radiator (extended the electric lines) plugged into the '93 thermostat housing, and my temp guage seems to be pretty accurate. My electric fan never kicked on correctly before the swap, so I wired up a toggle switch on the dash to use while the Jeep is in traffic on on the trail. I used a stock wiper fluid reservoir bottle in the old overflow bottles location as my new open system coolant overflow bottle.

I did not have to cut the crossmember on my 89 either.

When I changed my radiator over the fill neck was close but it fit, just make sure you do things carefully so you don't put pressure on any parts of the radiator, no need to stress anything on a new install.

I grabbed a MJ over flow bottle, it fits tight in-between the stock air box and the fender but it fits and works well, and is very close to the neck on the radiator.

With all that has been said, I would have to agree if you just having problems with the bottle but have had success with the system otherwise, go the cheaper and easier route and get one of the suggested metal bottles. Staying closer to what is stock and what you have experience in will most likely be easier in the long run, less guess work changing one thing than changing hoses, radiator, electric and whatever else.

GSequoia said:

I did not have to cut my '89.

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Me neither....dropped right in.....

I'd be curious as why to you go thru so many "turtles". I'm still running the original on my '90 and I overheated the thing once so bad I thought it would melt but its still intact, probably just jinxed myself......lol

Well, I just replace mine at intervals because I can get them fairly cheaply, and then I KNOW how old the thing is and what I can expect it to go through...

I get caps with them, so my spare (new) caps are still in the glove boxes, where they should be.

I do carry an old football in my XJ - just in case I break the one there - but I haven't needed it yet. Typically, it's the one I just replaced, with five years on it.

I've dealt with some severe overheating issues (usually due to belt failure) where I thought I'd fail the football, but that doesn't seem to have been a problem. Go figure...

In short, I'm just a big believer in periodic maintenance, and with my wife driving these as well, I don't see any reason to cause her any trouble...

5-90