MikeTassjeep10

Hello guys,

1989 xj 4.0 6 cyl

I have been reading a ton on converting to an open system cooling. I feel it's a good idea to get rid of that pain in the ***** coolant overflow bottle and get the rad with the filler neck built in it. Do you think that this is a better alternative? How difficult is it to re route every hose? And what else do I need to convert? I know you can get a newer heater valve to simplify it. Also any websites? Thanks

Firestorm500

I personally don't see any operational advantage to converting.

I have an '87 Renix with the closed system and a '92 HO with the open system.

Each works just fine as intended. The '87 may run a tad cooler. Both have a Mopar 195* thermostat.

Plastic radiator side tanks and filler necks crack and rupture too. Nothing lasts forever.

MikeTassjeep10

Makes sense. My 89 runs cool just an idea. My tank swells but that's part of it I guess. Just have to get a newer cap on it.

djb383

As stated, there is no engine cooling advantage, open vs closed. Personally, I prefer a closed system..... when hot, u can easily open (if needed) a closed system without hot coolant spewing everywhere when removing the cap. Either system requires a bottle.

If one does not understand how the different (open vs closed) pressurized cooling systems work and how a coolant recovery (open) system functions, a whole new can of worms can be opened up.

highmileage

The only reason I swapped to the open system was due to need for replacement, budget, and parts that were available.
For mine I pulled the system out of a 93 XJ, take the radiator(a radiator out of a 91 will allow you to keep the factory sensor location), diverter valve(you can delete this), T-stat housing and the sensor(if you need the sensor port).
If you pulled a 92 or later system when you go to do the wiring don't hack it up make a proper jumper wire for the harness, that way if you go back to the old system you're not having to wire it back in.

Parsnip

Honestly I went from closed to open the cheapest route, and also because the hcv is a pain in the ***. I used a pressure cap unit off a 99 Durango, and about 4ft of 3/4 hose, and a open system bottle I found in the jy. I'm in the conversion for all of 10$

rgr4475

Yup, mine cracked last week after that really cold spell. Had a 2 inch crack and a pin hole leak on the plastic tank. I replaced the radiator this past Monday when thankfully it hit the mid 50's here.

EvstaG

Here you go.

djb383

One could shoot a few holes in that 3 part video. Again, drilling a hole in the flange of the Jeep 4.0L t-stat does nothing more than slow down motor warm-up. Part 2 shows the dime size hole (in the head) directly beside the stat that flows/bleeds coolant/air the moment the motor is started.

redrunner

Why go to all the work. Get a cap/T you put in the upper hose replace the bottle with an overflow all for about $25 and good by close system and hello to the open system.

I put two different new pressure bottles on my 89 then switched over to an open system and would never go back to the bottle closed junk.

my $.02 worth

djb383

Those "cap/T you put in the upper hose" thingys can have/create issues as well.....they place the rad cap close to the water pump and high coolant flow can push the inner seal in the rad cap open allowing coolant to escape thus causing a low coolant situation inside the motor while the motor is running.

Parsnip

On the upper hose going to the thermostat housing?

Firestorm500

Which THEN causes overheating thereby blowing the head gasket and cracking the head.

Which THEN generates a whole 'nother series of threads.

djb383

Yep.

djb383

Double yep.