So I recently acquired a 1989 Cherokee XJ from someone for REALLY cheap. However, I'm entirely new to the world of Jeep and I've been learning so much already by skimming the forums. However, there's a pressing question that I have and I can't seem to find regarding the conversion of the closed system originally in the 1989 and the open from grand Cherokee etc...

The previous owner told me he did the conversion, but I'm confused because the overflow bottle is empty and has remained empty. I dumped half a bottle of coolant into the radiator because I wasn't sure whether or not the tank is supposed to be full at all times or...? I understand how open cooling systems work, but what I am really curious about is whether this conversion doesn't allow for the pressure required to re-uptake the coolant back to the radiator.

So my question is this: Does the tank stay empty and you just fill the radiator or is it a good idea to fill the tank? Sorry again for my noobiness, but ya gotta start somewhere I've been a GM freak...know a lot about the Chevy Trailblazer etc.. but Jeep not so much.

 

Overflow reservoir should always have coolant in it. If you add coolant to it but then it empties you probably have a leak or blown head gasket.
Also possible that the previous owner didn't do a proper conversion. It would help if you could post a picture.