Closed to open cooling system Q's

I am planning to convert my MJs closed cooling system to open and was wondering what all this BS is about a new heater control valve. Why couldn't I just run one inlet hose from the waterpump housing and one outlet back to the thermostat housing like my 97 XJ does and elimnate the valve. I don't have an aux fan on the MJ so do I still have to switch thermostat housings?

If you're planning on eliminiating the valve, I assume you don't want heat in the winter. The new heater valve is a better design that bypasses the pressure bottle, and also bypasses the heater whenever the AC is on, making it work less hard, and it really cleans up the mess of hoses in the back corner of the engine bay since all the hoses run to the Heater valve instead of to the bottle as well. It's only $16 at the parts store, so just keep that in mind.

Also, for the aux fan, when I did my conversion, the new radiator came with the plug for the electric fan sensor, so I didn't have to put in a new thermostat housing. I got the GDI radiator from Advance Auto parts by the way, it seems pretty good for $125, and has a lifetime warrantee.

You're also going to need a new coolant bottle and some 1/4" hose. The generic ones work just fine and I just screwed my new one into the existing holes using the metal bracket it came with. All in all, I love my new open system, it doesn't overheat, and it's much easier to watch the coolant level and flush without having to worry about burping the system.

i reused the original heater control valve, i just cut the rest of the other tubes off of it and now its a single tube with a vavle in the middle. i also relocaed the vacuum res to where the old expansion tank was. i also used the autozone GDI unit. i eliminated the A/C systems and removed the aux fan after it didnt matter that it wasnt working anyways. puke jug is actually a gatorade 32oz bottle tucked into the corner ahead of the airbox. i also used a dose of Water Wetter when i refiled the system. runs 190 all day.. hottest day this year it hit 200 at idle once. no complaints except the GDI DRAIN PETCOCK SUX! to big, odd shaped, and really too tight for the 2 finers you can get in there. i broke one because it was laeking and i couldnt figure it out so it got the pliers.

Pray, why go to the trouble? The only real issues with the RENIX "closed" cooling system are these:

1) The OEMR radiators have a service life of about 120-150kmiles. This is also common to the HO radiators as well. Go with Modine or Performance Radiator in the aftermarket - problem solved.

2) The plastic "volume" tank. It's not a problem as such, but it should be replaced every 7-10 years (I tend to date mine when I install them.) Change the cap and tank together - you can usually get them together for about $20.

There is NOTHING wrong with the closed system in comparison to the open - so there's no need to convert. See my various posts on the subject of keeping the XJ cool - I've beaten this to death time and again.

Keep this in mind - if the "closed" system is so bad, why is it being seen more and more often as OEM? I don't mind improving things, but I don't see a point in doing unneeded work.

5-90

I did the open conversion after a few issues with the closed system. If you're bottle splits you're truck wont cool correctly. None of the parts stores carry pressure bottles only overflow bottles and you can't wheel if you can't keep it cool. Refilling the system through the pressure bottle takes alot longer and the system can be tough to burp which isn't required with the open system. If you're closed system is in good condition theres no reason to convert but if you're replacing the radiator the rest of the components are cheap.

Another option is to simply swap in the newer style radiator so you get a radiator cap.

Jeep on!
--Pete

ComancheClub.com

As Riley points out the obvious, break out your hacksaw and whack off all the other BS and keep the same heater valve. Works great on my conversion. If it needs a radiator by all means swap to the newer style. Mine did not as the previous owner had recently put in a new 3 core. I lost the "volume" tank duringsome work under the hood and put an inline filler neck from summit in the upper hose.

the easiest thing to do is to go to the local U-PULL-it and find a mid-90's
Chrylser product....they will have a coolant reservoir in the same location as your jeep, except that they are much thicker material, have a REAL radiator cap, and an overflow pipe if the pressure gets too high. Get the hoses with it and its a simple swap...remove the mounting bracket for your original reservoir (2 bolts) and drill two holes to fit the new bottle to the sheet metal ledge....