Question regarding closed to open cooling conversion
 

Doing some more work on the old renix today and looking over the cooling system. Looks like the previous owner replaced the radiator at some point. The current radiator has a cap on it which leads me to believe it was replaced with a later year rad. For some reason tho there is no hose connected for the overflow near the cap, I’m assuming because the original bottle doesn’t have a place for the overflow to connect.

im thinking of going thru the open cooling conversion which would eliminate the heater control valve.

wondering tho if I can do the conversion and still retain my air conditioning? I haven’t seen any videos or write up where the ac is kept in tact and is still usable?

Do you still have the expansion tank just above the blower motor? If you still have the heater valve, perhaps the PO switched out the radiator but did not do the full conversion.

Converting to Open does not impact the AC.

looks like the whole system is the original closed setup with expansion tank and heater valve. Only the radiator appears to have been changed. No hose on the overflow has me kinda confused

without switching to a newer tank, where else would the overflow go?

thank u for pointing out about the ac. Not sure why I assumed it was all in the same component. That makes things much easier

Add a universal recovery tank and ditch the old pressure bottle. https://www.oreillyauto.com/shop/b/e...grand-cherokee.

Yeah, just get some new hoses to the heater core (make sure the flow direction is correct) and ditch the remainder. Then run a smaller hose from the filler neck to the bottle. You can mount the bottle pretty much anywhere but the old expansion bottle location is as good place. You just need to run the overflow hose all the way around to the filler neck. Also make sure you cap off the vacuum line that used to go to the heater valve.

I would definitely finish the conversion and kick that failure-prone football and heater control valve to the curb.

The cap on the surge tank is likely a lower pressure, so the cap on the rad will never open. Check the PO didn't epoxy it closed though.

I done this conversion six weeks ago

used this tank...
https://www.oreillyauto.com/detail/c...cherokee?pos=1

remove the old pressure tank, remove the shelf it sits on. I installed the new overflow tank on the innerfender wall where the old shelf was. I made a sheet metal bracket to bolt it too. I used a hammer to dent the inner fend3rwell a bit to give clearance to one corner of the new tank to assure it sits low enough so the hood dont hit it, just a 1/4 inch or so, minor denting with a ball ping hammer. works perfect. I eliminated the heater valve, and used the late model two heater hoses, but you will find that one of them hoses wont reach the water pump, so cut and splice the old hose from the pump to fit, easy peasy. the electric fan thermoswitch was originally on the renix radiator. the later systems moved this switch to the thermostat housing some radiators with the filler next might has a port for the switch, if not you need the late model thermostat housing to hold the switch, and that switch will be a different thread size, so you will need the later switch.

my conversion is nice i like it, no more failure prone plastic pressure tank!

thank you all, im gonna go forward with this conversion. From everything ive read online its just a matter of time before the current bottle explodes. Not sure if it ever happened before but if I can avoid it I think it will be better in the long run. Appreciate all the info, Ill be sure to post an update once i finish the conversion

Just a quick question regarding the vacuum lines, Theres one line that goes to heater control valve that is to be capped off if Ive read correctly. The other vacuum line coming out of the heater core goes to the vacuum canister. Does this line stay connected to the canister or should this also be capped off?

also for this conversion my plan is to run the heater hoses directly to the heater core, Ive seen a couple videos and writeups where some people use a newer model heater control valve. What is the benefit in adding a newer control valve? Is it just to keep warm coolant from being in the in the core at all times?

Keep the line to the vacuum reservoir. That operates the vent doors in the dash. Plug/block the one to the heater valve.

thank you, any idea about using or not using a newer control valve?

It's plastic and eventually prone to breakage. Jeep ditched the whole thing in '97.

**update I’m about 90% finished with the open cooling upgrade. I went with the Amazon radiator made by spectra. Everything installed fine except the temp sensor. The old renix temp sensor is too big for the opening on the rad. Would I be correct in purchasing a temp coolant switch from a 91 or newer cherokee? It looks much different from the renix style might need to modify the wiring some

If you get the thermostat housing for the '91 or later, it has the bung for the switch. You can then use the '91 or newer switch and just extend the wiring to get to it.

I didn’t I got a housing for an 87. Might need to swap that out I’m not sure what size switch fits into the rad I bought. All the videos I’ve watched and write ups recommend this rad from spectra

ill change the housing and use the switch from a 91. By chance do you know if there’s a pigtail available that I can splice into my existing switch wring?