Changing from a closed cooling system to an open one

[RLCollins]

I want to thank everyone on this site for being open and friendly to us that are just get started down this road to adventure land with our toys.

I have scraped my old closed cooling system in my 1989 MJ long bed 4X4 with a 4.0 HO, with 162,000 miles. I was at the u-pull yard yesterday looking for other parts when I found a copper radiator in a 1993 XJ with a 4.0 that was an open system. So I pulled it out along with the overflow bottle, and installed it along with a new fan shroud. I Had to relocate the high voltage ignition coil to make room for the long coolant overflow bottle.

There just two problems; the radiator that I installed does not have an opening for the radiator temperature switch, What do I do :hmm:

The other problem is in relocating the high voltage ignition coil, what choices do I have as far as distance from the distributor; how close or how far? Does it matter which position it is installed verticality verses horizontal or does any of this matter? :nuts:

What should I be concerned with?

again I just want to thank everyone for the friendship as well as the information, maybe one day when my MJ is where I want it to be, or some where close, I will bring it out for the ride. Just getting started on this project. :bowdown:

[Pete M]

I believe the HOs have the temp probe in the t-state housing. grab one of those on your next trip. :thumbsup:

[Eagle]

The HO does have the sender in the thermostat housing, but the stock 1989 sensor from the radiator tank won't fit the hole in a thermostat housing. And you can't use the HO sender, because the old sender is just an ON-OFF switch, but the new style is a variable resistor that sends actual data to the ECU and the ECU (on the HO system) in turn controls the aux fan.

 

There are a few (a VERY few) senders that will fit the t-stat housing and that are just switches. And I don't remember what they are. IIRC, BLHTAZ had some info on that, so you might try searching with BLHTAZ as the user name and the terms of your choice for the search terms.

 

Or just wire it to a toggle switch on the dashboard and control it manually.

[mjeff87]

if you can locate a 2.5 overflow resivoir, you can run it instead of the HO one.....it tucks nicely between the airbox and the fender on the driverside with a few minor mods.

 

I swapped a 4.0 drivetrain into my 2.5 MJ and retained the 2.5 overflow because I didn't want to move the coil/PDC stuff. All you really need to do is relocate (or eliminate in my case) the EGR solenoid and associated vaccuum system, and tuck the wiring harness loom under the airbox carefully. And relocate (or eliminate) the fuel pump ballast resistor ;)

 

Jeff

[cherokee]

I found that Tracker/Sidekick/etc. bottles are a good size to fit in the space left behind by the closed system coolant bottle. I've currently got one mounted on a simple bracket off the vent canister bracket.

[HOrnbrod]

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=15847&p=160108&hilit=fan#p160108

[RLCollins]

Thank you for all the great information, I truely consider this a joint effort. Anyway; back to the project. I was at the pull yard looking for other parts when I spotted a copper radiator in a 1993 XJ. This is an open cooling system, I have had nothing but boil-over problems with the factory installed close system. I even tried buying new factory plastic screw tops. This did not change a thing. So it is time to junk the old closed cooling system.

After removing the radiator and the coolant reserve bottle from the 1993 XJ, I firgured that was everthing I needed to complete this job. Not so from what I have read from the above input. I forgot about the electric cooling fan thermal switch that was mounted in the old system radiator. The copper one I pulled did not have a threaded hole in the radiator for this switch. I found out when I was installing it in my truck. What do I do? from what I read in the information that you all have provided above, it is in the thermostat housing, but - this is not just an on / off switch? :help:

Next item - I had to move things around so the new coolant reserve bottle would fit. The first thing in the way was the high voltage ignition coil. It was mounted at the bottom of the fender well, or the top of the coil spring mount, in a 90 degree bend piece of metal to keep the coil from bottoming out on the fender well. the coil is somewhat round, so it has to be elevated about an inch for proper fit. I straighten this piece of metal out flat, so the coil went from laying down, to standing up close to the distributor, and just behind the AC compressor. Is this a probllem? This gave me the depth I needed for the new coolant reserve bottle. The bottle also had two upper supports, I had to cut this support in half to make it work at the new location. I dry fitted it first, to obtain correct marks for drilling the holes. Next was to remove the wheelhouses or inner fender, which I encountered rusty fender bolts and the brittle plastic inner fenders. There must be something better to replace it with. Next was Drilling the holes for the bottle supports and bolted them down to the fender. Next was the four relays on a rack along with two test ports, which I moved closer to the right fender, and screwed all these items above down with 1/4 - 20 bolts through the fender well.

Next was the starter relay, mounted it on one of the upper support arms to the coolant bottle, its real close to the battery, but you still can service the starter relay and the fusible links without unscrewing anything. Turn out to be a real nice fit. thanks again for the information

PS I have just two problems

one was when I was cleaning up the electrical wires, and vacuum hoses along with strapping everything down tight - I ended up with a blue vaccum line from the transfercase with no where to go. This is in the bundled of lines colored yellow, green, red and blue. any ideas :dunno:

The other problem is with the auxiliary fan thermal switch and the thermostat housing mounted one, with it being an on / off switch verses a information sending unit; any ideas? :headpop:

This is the third time I have tried to write this information down, because I keep loosing it, from not understanding this system yet

Be patient with me - I am slow

[Eagle]

All that work for an "upgrade" that doesn't upgrade anything. I know I am in a small minority, but I see no reason whatsoever to go through all the modifications you are going through.

 

The simple solution to your aux fan issue is to unplug the old sensor that was in the radiator tank. Clip the sensor off the wires, and run a pair of wires from the remaining pigtails through the firewall to a toggle switch on the dashboard. Plug the connector back in where it was. Control the fan manually when necessary for overheating. It will still function as before when the a/c cuts on.

[RLCollins]

Upgrade - what do others think of the old closed type system with the coolant pressure bottle with the plastic screw on top? Has anyone else had a bad experience with this system. What do you think? :popcorn:

[Pete M]

the closed system allows the engine to comfortably run at a hotter temp and a hotter engine means better combustion. Or so the theory goes. Not sure if that translates into real world numbers, but Jeep is far from the only manufacturer to use the concept. My neighbor's Caddy has it.

 

People seem to badmouth the closed system, but I notice that most of their issues stem from 20 year old parts.

[mvusse]

I had a problem with the bottle cracking due to 21 year old brittle plastic. Got a new bottle, less than a year later the cap didn't want to close tightly. Got another cap from the junk yard and it's good again, for now.

 

I will convert to open at some point in time, because I'm tired of messing with plastic caps. Give me a good old fashioned reliably metal radiator cap.

[comanche09]

I found that Tracker/Sidekick/etc. bottles are a good size to fit in the space left behind by the closed system coolant bottle. I've currently got one mounted on a simple bracket off the vent canister bracket.

 

Cool

 

Do you remember what year you pulled it from? Thanks

[RLCollins]

I pull my parts from a 1993 XJ :USAflag: