^^^^^This.......and it's so easy to test a stat in a pot of water, on top the stove, using a cooking thermometer. Do not toss the stat into boiling water. The stat is the only cooling system component that can tested easily at home, no special tools. And as stated above, run the motor without a stat for a test....see what the results r. Probably no difference....it just sounds like the cooling system has been neglected too long and needs to be totally replaced.

I would never recommend just throwing money/parts at something.....except for the XJ cooling system. Compared to a whole bunch of other vehicles out there, parts for the XJ cooling system r incredibly cheap and if the motor is cold, the parts can almost be replaced blindfolded.

 

Decided to do the open system conversion. I'm going to replace everything but the core. Might as well convert it while I'm at it.

While doing so, I noticed the vacuum valve to the heater core was garbage. Would that have caused this whole mess? Especially since I didn't have heat? I do have a new one, but I am not staying closed any longer.

I am also on my 30th gallon of water flushed through the core.. ugh. It is clear water tho. (Now) any tips and hints for open system?

Thermostat housing hose goes to the bottom of the core? Water pump hose to the top. Correct me if I'm backwards.

Do I just plug the old vacuum hose that used to go to the switch?

 

I presume u r changing over to a "open" style radiator and radiator cap, correct? I ask because a "closed" system can be converted to "open" even though a closed system radiator is still used. Depending on which style radiator is used determines which conversion process u use. The nipple just below the rad cap must be plumbed via rubber hose to the bottom (very important) of the recovery bottle and the new or converted recovery bottle must not hold pressure....it must be vented or "open" to the atmosphere. The bottle should be mounted about the same level as the top of the rad. The radiator cap is critical to a coolant recovery "open" system functioning properly.

The vacuum line opens/closes the heater control valve....an inoperative heater control valve will have nothing to do with the motor overheating.

Look closely at the heater core nipples at the firewall. U'll see that the 2 nipples r 2 different sizes/diameters....5/8" and 3/4". The water pump has the small heater hose nipple and the t-stat cover has the large heater hose nipple. 5/8" to 5/8" and 3/4" to 3/4".....pretty simple.

Plug/seal the old vacuum hose.

 

Correct. I have a 2000 cherokee that I'm taking parts from. I have an "open" radiator. Along with the "open" overflow tank. I also have the hose from the cap ran to the tank. All I need now is some hose splices to complete the lines from the front of the motor. I sure hope this fixes my problems. Everything seems to be working nicely so far.

 

I would recommend that u not "splice" any heater hoses. Get your tape measure out, measure from the front of the motor to the heater core nipples at the fire wall, and add a little extra. Go down to your local auto parts store and buy bulk 5/8" and 3/4" heater hose in the lengths u measured. They have the stuff on big rolls and sell it by the foot.

Do u have any idea of what condition internally the conversion radiator is? Replacing an older plugged rad with a newer plugged rad won't accomplish anything. There is absolutely no advantage to "open" vs "closed" systems with regard to cooling efficiency.....one is just as good as the other.

 

Perfect. Thanks for the input.

 

Conversion complete. I let it idle for about 15 minutes and everything seemed to be staying cool. I still have a little dirty back flush into the res tank. But NOTHING compared to what it was. I'm happy with the outcome so far. Considering how easy it is. I recommend it for those who are tired of the closed system. I'll post again after taking it for a drive. Time to register it finally

 

Oh, and my heater works now too. Bonus. Since winter is on its way.

 

Good job.......keep a close eye on that "Lev-r-Vent" rad cap.......they r known to leak.

 

10-4.

Side note. The 00 radiator doesn't have a spot for the fan temp sensor. I plan on putting the fan on a manual switch in the cab. It still works with the defrost trick until then. Just found it weird that it didn't have a spot for it.

 

Could u use the '00 t-stat cover with a late model coolant temp sensor in it?

 

I suppose I could. It would take some rewiring since this old connector is down by the lower rad hose. It would probably be easier to ignore, and make a switch. ?

 

I'm just don't like a manual efan switch (unless u drive thru a lot of high water crossings). Having the efan activate automatically is safer......but that's just me.

 

I'm with Djb, prefer it automatic. Booger is, IIRC the switch is pretty large thread, 3/4 or 7/8? Idk what the later housing has.

 

Yes it would be nice to be auto. Thing is, I'm not sure it ever even worked. The 25 years it's been alive, it's just one of those things I looked after. Plus, I've had cooling issues for a while on both my jeeps. So I'm used to switching it on. (Defrost on the 89) my 00 is manual too.