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DIY convert from closed to open cooling.

This Write up is how I converted from closed to open cooling. You may choose other parts to achieve the same end result.

I am converting because I am tired of messing with the pressure bottle, to remove the heater flow valve, and replace old hoses.


Parts:

  • Radiator with filler neck $82.57 *

        Part number: CU1193

  • Radiator cap $24.99 * (I bought a fancy cap with built in thermometer.)

        Part number: 2471S

  • 2 Gallons antifreeze coolant $14.99 ea ($24.98 for 2) ***

        Item number: 7020022

  • 10' 5/16 hose $19.90 ***

        $1.99 per foot
          Item number: 5194083

  • 4' 3/4 heater hose $5.56 ***

        $1.39 per foot
          item number: 5192978

  • 4' 5/8 heater hose $5.56 ***

        $1.39 per foot
          Item number: 5192951

  • Two 3/4 to 5/8 hose adaptors $2.99 ea ($5.98 for 2)***

        Part number: 80424

  • A junkyard radiator bottle (I think mine was from a ZJ or WJ dad snagged it for me)

Total conversion cost: $169.54 + S&H and tax
 
Optional Parts:

  • Later model thermostat housing with temperature switch
  • new water pump
  • Dual Fan Controller
  • Second Electric fan for dual conversion
  • Wire
  • Relay or Fan Controller
  • Power Switch
  • MJ or XJ 2.5L Radiator Bottle $16.99 **

        Part number: 52003213

  • MJ or XJ Bottle Cap $7.97 **

        Part number: J3223202
 
Ordered from:
Amazon.com *
Morris4x4.com **
Advanced Auto Parts ***
 
 
Tools:

  • Gloves
  • Safety glasses
  • Knife or box cutter
  • Phillips and flat head screwdrivers
  • Bucket
  • T-25
  • T-30
  • 8mm Socket and or wrench
  • 10mm Socket and or wrench

Getting Started
 
15299415736_615fc7027b_o.jpg
 
Start by draining out the old radiator fluid, removing the upper and lower radiator hoses, fan temperature switch, and if you have an auto transmission the transmission cooler lines from the radiator.  Use an 8mm socket or wrench to remove the electric fan and clutch fan shroud. 
 
The radiator support is held on by several bolts 10mm and T-25 or T-30 (sorry mine where all stripped before I started not exactly sure the actual size).  The bolts removed connect the support to the frame and front clip, then they are all out remove the radiator support.
 
15135900917_8f9216a186_o.jpg
 
The radiator should come out without much fuss.
 
15299394456_98c352ac83_o.jpg
 
With the radiator out of the way now would be the perfect time to convert to Dual electric fans and replace the water pump.  Sadly I was running out of time due to fighting with stripped bolts so i was not able to do ether....
 
Depending on the radiator you get you may not need to change the thermostat housing.  My thermostat housing is from a later model XJ, and can use a temperature switch. However the radiator I purchased has the hole for the fan temperature switch.
 
Remove the 3/4 hose and the 5/8 hose from the thermostat housing and the water pump.
 
15299402386_3600dd95af_o.jpg
 
Remove the old coolant pressure bottle and the hoses going to the heater core.  Cutting the hose may be needed.
 
15135676460_d55faa4197_o.jpg
 
The new hoses will need to be adapted from 3/4 to 5/8, the reason for this is the thermostat housing outlet is 3/4 connecting to the heater core that is 5/8, and the heater core outlet is 3/4 connecting to the water pump inlet that is 5/8.   After all the old hoses are removed take your new 3/4 and 5/8 hose and route it however you like, then measure where to cut the hose in half.  Use the 3/4 to 5/8 adapters as needed.  
 
Again the hose routing is:

  • 3/4 from thermostat housing
  • 3/4 to 5/8 adapter
  • 5/8 to heater core inlet
  • 3/4 from heater core outlet
  • 3/4 to 5/8 adapter
  • 5/8 to water pump

15135719407_c13b8f0990_o.jpg
 
The new coolant bottle is the next challenge.  I ordered a 2.5L MJ/XJ coolant bottle that should fit on the drivers side fender, I will likely need to go back to a cone air filter to make room for it. Till I decide for sure what bottle I am sticking with I used one from a Junk yard Jeep and slightly modified it to work.  I had to remove the old pressure bottle "shelf" to make room. I used a self tapping screw to attach the radiator bottle to the back of the engine bay where the old bottle was located.  I routed the 5/16 hose around the back of the bottle and used the heater hoses as a bridge, ending where the radiator filler neck will be.
 
15135547290_7ec4b87ce4_o.jpg
 
Install the new radiator and reconnect the upper and lower radiator hoses.  Reattach the radiator support.  Connect the Coolant bottle hose to the filler neck.  For good measure I zip tied all the new hoses in place.
 
Fill the radiator system with 12 quarts (3 Gallons) of coolant. Must be a 50/50 mix, you can use pre-mix or concentrate with distilled water. you may not be able to fit all 12 quarts as there will likely be some coolant still in the engine. Bleed the air out of the system, Renix engines have a coolant temperature sensor on the back of the head accessible from the engine compartment.
 
Clean up and all done
 
Prior to this conversion My Jeep would boil over in 20 minuets and interstate travel was a no go.  Now the temperature has yet to pass the 210 mark while traveling 75 mph on the interstate.  A side note, my A/C seems to be blowing cooler as well now....

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  • 6 months later...
  • 2 months later...

It looks like like you replaced the jumble of innerconnected hoses coming off of the thermostat housing and had two hoses directly to the heater core.  And you took the overflow hose into the reservoir bottle.  You left the two, upper and lower, radiator hoses as is.  Is that correct or am I missing something in the pictures?

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It looks like like you replaced the jumble of innerconnected hoses coming off of the thermostat housing and had two hoses directly to the heater core.  And you took the overflow hose into the reservoir bottle.  You left the two, upper and lower, radiator hoses as is.  Is that correct or am I missing something in the pictures?

 

the radiator hoses are left alone.  

 

Hose Routing:

Starting at the thermostat housing > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 heater core inlet (bottom) > 3/4 heater core outlet (top) > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 water pump inlet.

 

Overflow:

from the filler neck (there should be a little port) > 5/16 hose > Open cooling overflow bottle

 

If you need and extra pictures let me know

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Hose Routing:

Starting at the thermostat housing > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 heater core inlet (bottom) > 3/4 heater core outlet (top) > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 water pump inlet.

 

 

 

If you need and extra pictures let me know

 

 

 

That is perfect right there.  I am going to make that change and add a reservoir bottle.  The next question is, an forgive me for this but I have to ask.  I still need to turn the engine on and fill the radiator through the radiator.  Not fill the overflow reservoir.

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Hose Routing:

Starting at the thermostat housing > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 heater core inlet (bottom) > 3/4 heater core outlet (top) > 3/4 hose > 3/4 to 5/8 adapter > 5/8 hose > 5/8 water pump inlet.

 

 

 

If you need and extra pictures let me know

 

That is perfect right there. I am going to make that change and add a reservoir bottle. The next question is, an forgive me for this but I have to ask. I still need to turn the engine on and fill the radiator through the radiator. Not fill the overflow reservoir.

Correct fill it through the radiator cap, but make sure you also have fluid in the overflow bottle.

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  • 2 weeks later...

you can also simply use two length of 5/8" hose, they will fit over the 3/4" fitting ends easily enough (both my XJ and my MJ are done this way). A little sunlight (or whatever your favourite dishsoap is) helps slip the 5/8" over the 3/4" ends.

 

I used a 92 XJ overflow bottle and PDC bracket "massaged" to hold the Renix relays and such, had to drill 2 holes but it fit right in. mounting the IGN module was tricky afterwards though ... in that pic it was zapstrapped to the bottle.

 

Later I mounted it to the firewall where the original pressure bottle was.

 

 

Just as further examples of how things can be arranged. I also added a later model heater hose nipple when I swapped water pumps which made things easier as well. My first overflow bottle was actually a Fast Orange bottle, I converted with some old fuel lines to draw from the bottom worked quite well and fit beside the air cleaner (mostly because it was semi-squishable).

 

Blue88Comanche - do you get oil drips from that breather filter? I was thinking of trying the same thing on mine.

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  • 4 months later...
  • 2 months later...

Hi everyone,

 

Does it matter which direction coolant flows through the heater core?

 

Would there be a problem just using three-quarter inch hose on both three-quarter inch fittings, and 5/8 inch hose on both 5/8 inch fittings? That would reverse coolant flow through the heater core, but I don't see that that would cause a problem.

 

Thanks!

 

Gene

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Hi everyone,

 

Does it matter which direction coolant flows through the heater core?

 

Would there be a problem just using three-quarter inch hose on both three-quarter inch fittings, and 5/8 inch hose on both 5/8 inch fittings? That would reverse coolant flow through the heater core, but I don't see that that would cause a problem.

 

Thanks!

 

Gene

 

Heater core input is on the bottom, output is on the top. this helps when purging the air out of the system.

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I replaced my lines with 5/8" hose all around. Tighter fit on the 3/4" fittings but not an issue with a little lube.

Did this for both my 88 MJ open system conversion and my 00 XJ.

I also swapped the Renix water pump elbow for a late model HO style elbow when I converted. Gets rid of one move soft hose bend is all.

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  • 5 months later...

How is this set up holding up for you? any changes? Gonna do this soon about to order the radiator

So far I replaced the grand Cherokee bottle with a stock 2.5L bottle that's located next to the airbox I haven't had any issues with it. The ZJ bottle on the firewall would boil over for some reason all the time, but now t the 2.5 XJ/MJ. The part number is above.

 

I think the only reason why I'm occasionally overheating on the interstate now is because my water pump might need to be replaced. That's the only part of the cooling system I haven't replaced.. I can't imagine the exhaust manifold leaking into the engine compartment is helping anything as well.

 

 

Sent from my iPhone using Tapatalk

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  • 7 months later...

what was your way of purging the air out of the system? I usually start the engine and let it warm up close to operating temp, shut off the engine, let it cool a bit till the radiator is 'warm". then open the radiator cap. Repeat maybe one or two more times.

I have the newer thermostat housing, so I just loosened the temp sender till I thought most of the air was out. Then let the system naturally burp itself.

 

 

Sent from my iPhone using Tapatalk

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  • 3 weeks later...

I stayed with the radiator already in the truck and used the Moroso water neck part no. 63730. I have the no spill funnel that works great on my YJ but it doesn't fit this water neck. :doh:

My driveway has an incline, so I jacked up the front end and pulled the cap letting the bubbles out while it warmed up. I did drill a small hole in the top of the thermostat before I installed it.

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