my 90 cherokee with the closed system keeps overheating. I have only overheated it badly once at first my e fan wasnt turning on and I found that to be a bad fan switch so I have it wired together to keep it on until my new switch arrives, but that didnt fix it so I put a new thermostat in today and flushed my radiator out as well. then I filled the rad with the upper hose and drilled a little hole in the thermostat to let air escape filled it up let it idle and it started going toward the red so I shut it down. My overfull tank has a pin hole leak also.
I pulled the spark plugs and chenged them to make sure I didnt blow a headgasket and they all came out dry but 2 of them have air bubbles coming out from where water was sitting next to the holes from filling the hose but I dont think I have them in tight enough is the problem. The upper hose is hot at the T-stat but cold at the radi so I'm thinking my water pump failed but I would like addvice to make sure I'm going the right direction. The radi is clean and looks to still be in good shape with no leaks.

sorry for the long post but this is my daily driver so I need it on the road quick.

 

you have air in your system, search burping , it explains how to get the air out. i did a headgasket and for two hours i couldnt get it to stop over heating. you just have to get the air out.

 

If the jeep didn't take the required amount of fluid, which I have no idea off the top of my head, then as mentioned above, you need to get the air out. And why did you drill into your thermostat?

 

fill it thru the heater hose outlet on the thermostat housing.

 

the return bottle needs replaced if there are ANY cracks or holes in it. i just bought one on ebay this week. i had the same problem you have a week or so ago. i replaced my water pump and flushed the entire system. now everything is goin' good. my return bottle had a couple small cracks in it. i used a heat iron to "weld" them shut, but once the engine reaches normal operating temp they would blow out again. i put a 195* thermostat in mine, but i wish i would have went with a 180*. to get the air out of this system, you need to fill the return bottle-run engine til it's in normal operating temp (210*). then let it cool off. after you have done this step a 3rd time, the system should be good to go. this is from the chilton book, and worked for my closed system. hope it helps!

 

yeah I found a new bottle because after doing the water pump and burbing the system as soon as I put the cap on and ran it, the bottle just blew the crack open and puked water. But its not overheating anymore.