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Converting Closed Coolant System To Open Coolant System In My 4.0L


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Is There Any Reason I Can't Use The Coolant Reservoir From The 2.5 Comanche In My 4.0 Comanche After It Has Been Converted To An Open Cooling System? I'm Curious Because I Obviously Cannot Keep Or Use The OEM Bottle and I'm not particularly thrilled with the idea of trying to make a bottle from a more recent year fit.

 

On another note, care to weigh in on eliminating the heater control valve?

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Originally my overflow bottle was a modified Fast Orange bottle with some brake line to siphon. Now I have a 92 4.0 bottle since I couldn't find a 2.5L bottle at the time.

Was it difficult to get it to fit in properly? I know I have some vacuum lines laying against the inner fender I just want to be careful not to pinch them.

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Which ... the 4.0 bottle?

Not really ... just used the HO bracket and added parts of the Renix bracket to it where needed.

The coil is currently zip tied to the HO bracket ... but I have a ZJ coil lead so I plan to move it to the firewall where the old pressure bottle was.

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No worries, has anyone given any thought to using an aluminum coolant bottle? Once. The original mounting bracket has been removed, there should be plenty of room for one. Although I'm not sure about capacity, I think it holds 800ml... Does anyone know if that would be sufficient or would I need something larger.

Once again It WON'T be the original closed system.

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This is a project I'm planning to do this summer. What parts are you using to convert it to an open system?

We'll the original reason I even started this project was because I bought this truck about 3 weeks ago and the more I dig into the truck the more things I find that the previous owner did wrong... IE: the Cooling system. They swapped out the radiator with an open radiator I believe from a 94 cherokee. However, they left the original pressure bottle... All they did was cap the bottom hose going to the heater and the bottle was no longer connected to the heater valve... The whole thing was a MESS basically and not done properly.

 

I am going to be eliminating the heater control valve unless I can find a reason not to other than AC doors being stuck open. So I bought 3ft of 3/4 heater hose

3ft of 5/8 heater hose

Around 6ft of 5/16 fuel hose (for the overflow bottle)

I am buying a new 195degree thermostat

Two hose adapters for 3/4 to 5/8 hose...(this is because in order to not reverse the flow through the heater core the 3/4 hose goes the the 5/8 on the heater core and vise versa.)

Since I am eliminating the heater control valve I had to cap the vacuum line to the valve so I got a pack of 1/8 inch vacuum line caps.

And I need to buy a new radiator so I'm going to buy one from teamcherokee.com. But those radiators I believe don't have the port for the sensor that turns on the auxiliary fan... Still trying to figure that out. I'll keep you posted

 

Still looking for a bottle as you see in my previous post^^

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It's already been swapped out and the radiator that I just pulled out is in bad shape. I appreciate the suggestion! Definitely would've been my choice if It was going to be possible, didn't think of that, thanks!

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I'm not sure what the minimum fluid capacity should be for the over flow bottle, but I'm sure anything above a quart should suffice.  The later model XJ bottle holds over half a gallon but as long as you have everything sealed good and the rest of the system filled correctly, the reserve in the bottle shouldn't fluctuate much.

As far as the cover you're referring too, it's just the stock one that I cut and modified.  I had to move the relay center over by about two inches towards the passenger fender well to accommodate the later model XJ bottle.  I also had to relocate the ignition coil.  I wanted mine to appear mostly stock.  See below:

 

 

 

I anchored the bottle in place with some bracket I had laying around...

 

 

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This is a project I'm planning to do this summer. What parts are you using to convert it to an open system?

We'll the original reason I even started this project was because I bought this truck about 3 weeks ago and the more I dig into the truck the more things I find that the previous owner did wrong... IE: the Cooling system. They swapped out the radiator with an open radiator I believe from a 94 cherokee. However, they left the original pressure bottle... All they did was cap the bottom hose going to the heater and the bottle was no longer connected to the heater valve... The whole thing was a MESS basically and not done properly.

 

I am going to be eliminating the heater control valve unless I can find a reason not to other than AC doors being stuck open. So I bought 3ft of 3/4 heater hose

3ft of 5/8 heater hose

Around 6ft of 5/16 fuel hose (for the overflow bottle)

I am buying a new 195degree thermostat

Two hose adapters for 3/4 to 5/8 hose...(this is because in order to not reverse the flow through the heater core the 3/4 hose goes the the 5/8 on the heater core and vise versa.)

Since I am eliminating the heater control valve I had to cap the vacuum line to the valve so I got a pack of 1/8 inch vacuum line caps.

And I need to buy a new radiator so I'm going to buy one from teamcherokee.com. But those radiators I believe don't have the port for the sensor that turns on the auxiliary fan... Still trying to figure that out. I'll keep you posted

 

Still looking for a bottle as you see in my previous post^^

 

Elimination of the heater control valve will not have any adverse effect on your blend doors. Do it. 

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Onlyinajeep can you fill me in a little on your vacuum setup in your pic?  I've been wrestling with vacuum leaks since i bought this thing.  Where did you get that canister?

 

That contraption I got hooked to the CCV breather?  It's just some screw-on style PVC ends with plastic elbows inserted on each end.  Inside, I have mesh (a scouring pad or brillo pad/steel wool) stuffed inside, and on the top side elbow, I have a small air filter attached.  This is the writeup I went by: http://www.jeepforum.com/forum/f12/i-made-_____-my-yj-post-your-homemade-jeep-stuff-here-457361/index6.html#post5039835

 

This is a better picture of mine.

 

I don't have it in place anymore because I've done an engine swap since then...  Every so often, I had to drain the oil back down in to the valve cover because it would like to collect inside and in the lower elbow (which was the point).

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Thanks for the link.

 

I did the conversion today, pics available if you want to see them.  Found that the original radiator was still in there after 25 years.  But I also found out that the electric fan isn't kicking on.  It runs when the AC is switched on so I know the fan motor is good.  What do you all think, relay or switch replacement in order?

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Thanks for the link.

 

I did the conversion today, pics available if you want to see them.  Found that the original radiator was still in there after 25 years.  But I also found out that the electric fan isn't kicking on.  It runs when the AC is switched on so I know the fan motor is good.  What do you all think, relay or switch replacement in order?

Jump the connectors at the tep sensor and report back. key On of course.

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