99+ Open Cooling System Mod

[rubiconron]

Has anyone completely swapped in a 99+ cooling system onto closesd loop renix era system (88 )? Through my searches I've seen several article about changing the heater control valve and some about deleting it etc. etc. I have a parts 99 that I can pull the entire system from and was wondering if there would be any issues.

 

99 Radiator

99 Hoses

99 T-stat

99 Water pump

99 overflow bottle

 

Are swapping all of these parts necessary? Do I need to change the water pump if its not having a problem?

 

Thanks

 

Ron

[maddzz1]

The problem most seem to have is that the temp sensor for the elec. fan is on the radiator on the closed system and not on the open. I think this is why you need to change the thermostat housing. But I havent seen a thread where anyone has got the fan to work yet although BLHTAZ I think is working on something now.

 

After looking at mine yesterday I noticed that if you don't have AC there is no elec fan and no temp sensor on the radiator. So if you don't have ac I don't think you need to swap the stat housing or worry about the sensor for the elec fan

[rubiconron]

I do have A/C. Not sure if its working yet. But it is there and I plan on using it this summer. Sooo I will most likely change the T-stat housing. I do have a brand spankin new T'stat to go in anyways.

 

Thanks for the help.

 

Ron

[BLHTAZ]

I did that swap and can tell you that it is not worth the effort to change all those parts. It did take me forever to figure out a way to make the electric fan work, but I finally did it with a Hayden adjustable controller.

 

My thread is here about it... http://www.comancheclub.com/forums/viewtopic.php?t=7928 Kinf of long, but you will see that it is not worth the effort. There are also a couple suggestions in there for ways to make an open system that are much easier.

[Oizarod115]

there is no reason to swap in an open system, just replace what's broken and run with it.

 

my brother and i both have the closed system and besides busting up radiators (flipping and rear-ending) we haven't had any trouble with it.

 

i had a gauge that read 60 degrees hot and ended up replacing most of my system's parts and she ended up running at 160 for a few months cause i swapped in a low thermostat to get the gauge to read at 210! DOH! :oops:

[offroader461]

here's what i have done twice with absolutley no problems, I used all 96 parts...runs cooler than before...i recommend it:

 

87 MJ:

swapped a 3 row open style rad

newer heater valve

Flow Kooler water pump

used a normal thermo housing (for the 87)

replaced the overflow tank

hoses new

 

90 XJ:

swapped in a 3 row aluminum open rad

replaced water pump with flow kooler

high flow thermo housing off newer 97 cherokee(just plugged the temp port)

Hoses new

replaced heater valve

new overflow tank

 

The MJ is a 5spd but the rad has ports for A/T lines and the thermoswitch for the fan..my fan is run off a switch in the truck and i never use it...on the XJ its a AW4 and the rad also had the trans cooler lines and the thermoswitch fitting in the radiator which i use an it works as it should

 

 

You don't necessarily have to change everything over just the radiator, overflow tank (or get a universal) and the heater valve..pretty much all i "swapped in"

[Oizarod115]

if waht you want is an electric fan that cuts on/off by itself get a large hose adapter made to fit one piece of rad hose to another and put a bung in the middle of it for a temp switch, then cut the lower rad. hose put it in, and wire her up. the orange wire going into the solenoid on the drivers fender should be the on wire for the fans.

[MiNi Beast]

http://www.comancheclub.com/forums/viewtopic.php?t=7695

 

 

 

Any help?

[Eagle]

I do have A/C. Not sure if its working yet. But it is there and I plan on using it this summer. Sooo I will most likely change the T-stat housing. I do have a brand spankin new T'stat to go in anyways.

That's not the issue. Read some of the other threads discussing this. The issue is that the auxiliary fan in the Renix years is controlled by a switch that mounts in the driver's side radiator tank. The '99 radiator will not have a bung for the switch to thread into, and the switch is MUCH too large to screw into the t-stat housing. Which means you will have to find an alternate way of controlling the auxiliary fan.

 

It seems like most of the free world has decided that converting from the closed to the open cooling system is a "must do" project, yet they ignore the fact that it provides exactly zero additional cooling capability and creates problems that still have not been 100% resolved. IMHO it's a waste of time and effort.

[rubiconron]

Eagle,

 

I am reconsidering the closed to open conversion. I am looking to make improvements to the current system which is most likely all 20 years old. I have only replaced the hose that runs from the inlet?? (smaller) of the thermostat housing to about half way down the valve cover where it is spliced, and I have a new thermostat.

 

Things that I may need:

thermostat housing (mine is kind of pitted)

radiator

water pump?? (i know that it has been replaced at least once by a PO)

hoses

pressure tank (its not leaking)

fan sensor (I don't think mine works) I know the fan is good electrically.

 

What suggestions do you have for improving the closed system? Like I said most of my stuff is OEM and has 20 years of abuse.

 

Thanks,

Ron

[LocoJeeper]

Just skimmed the thread... but there is another important difference in fan control ... the renix is on/off, the HO version is variable voltage. Roughly same end result but different process. So you can't exactly swap in a HO switch, as that won't send the right signal.

 

I bought (and have an extra one :-) a 90-something or other Corvette thermostat which is the right thread, the right temperature range, and an on/off switch to work on a renix to HO cooling system conversion.

 

I have a thread somewhere as to how this works... not my own discovery.

 

I'll find it if someone is interested.

 

God Bless,

 

Ben @ Loco4WD.com

[Eagle]

What suggestions do you have for improving the closed system? Like I said most of my stuff is OEM and has 20 years of abuse.

You don't mean "improving" the closed system, you mean "restoring" the closed system. Changing to an open system doesn't "improve" anything -- the radiator has exactly the same frontal area and cools exactly the same as a "closed" system radiator of the smae type from the same manufacturer.

 

The issue is that, after 20 years, the original radiator is probably clogged almost solid. IMHO it's a miracle it has lasted this long. I am now on the third radiator in my '88 XJ -- the original lasted 12 years, the replacement lasted 7 years. Just put in a decent new radiator and you should have no other problems.

[LEAD_NOT_FOLLOW]

I disagree with Eagle.

 

The 91+ cooling system conversion is worth every penny spent on doing the conversion. Getting rid of the pressure setup is worth any amount of money spent on the conversion.

 

No more finding t-stats with the bleader hole in them so you can get the air out of the system, no more stupid pressure bottle's that blow on you (even new ones), no more crappy heater control valves. Just do it and don't look back.

 

Yes I've spent a lot of money keeping my Renix era setup in tip-top shape and once I finally broke down and did the conversion it's a night and day difference. And as far as Eagle saying that their is no difference in cooling I disagree with that entirely. The new open-loop setup is so much more efficant that it cools so much better.

 

Just my penny and a half worth from someone who's spent a lot of time (and money) dealing with the cooling on the 4.0L's...

[Oizarod115]

idk, we have 2 closed system jeeps and 3 open system jeeps, (cherokee's and manche's) all 4.0Ls and the two closed system jeeps have ALWAYS run cooler than the open system jeeps.

 

not to mention how god awful it is to get an open system to drink coolant through the rad-cap.

 

i see no difference between the two that warrants spending any money to upgrade, if we lived in the desert and were overheating constantly i could see upgrading all the stuff and trying to make her run as cool as possible to prevent disaster, but that's not the case

 

from what i've seen just maintain what you've got and you'll have no problems.

 

and ALMOST EVERY 4.0L will need a replacement radiator at some point. its just life.

[Eagle]

The new open-loop setup is so much more efficant that it cools so much better.

I am certain I can't dissuade you from that opinion, but what you are proposing is physically impossible.

[jtdesigns]

Water has a higher boiling point when its under pressure.. What is the system pressure of the closed system?

[Eagle]

Water has a higher boiling point when its under pressure.. What is the system pressure of the closed system?

I don't think the FSM specifies a pressure. Never saw one. If the system is operating properly, it shouldn't matter. The normal operating temperature is 210 degrees, which is below the boiling point for unamended water at sea level. With either the second or the current (third) radiator in my XJ with the closed system, the temperature with a 195 degree t-stat never goes over 200. Ditto the '88 MJ, with the original radiator.

[rubiconron]

Should I step up to a 2 or 3 row radiator?

[LEAD_NOT_FOLLOW]

The new open-loop setup is so much more efficant that it cools so much better.

I am certain I can't dissuade you from that opinion, but what you are proposing is physically impossible.

Why is that physically impossible? I'd really like to hear your reasoning as to why it is... :roll:

 

 

Also it's been said that to keep the closed loop system in "tip-top" shape you'll at somepoint have to replace things. So if you do have to buy a new rad and a new pressure bottle (they like to crack!) than why not just get a newer style rad and the money spent on the pressure bottle just get the new heater control valve? It's not like if your spending the $$ replacing Renix parts that it's really any more cost to do the conversion....

 

Also, I'd do with a CSF 3-core over a factory replacement. I've ran CSF's in all my rigs and have been very happy with them. And yes I've even ran a Renix CSF before I did the conversion....

[Pete M]

Are we talking about the efficiency of the cooling system (its ability to pull off and dispose of the heat) or the efficiency of the engine itself (it's ability to run at the most fuel-efficient state)?