Renix thermostat question?

So, my 1990 cherokee is acting up, and it looks like I need a new radiator.
But I had a thermostat question.
A little background, this XJ hardly got used during the summer, as I have other things to drive. The XJ has always ran cool, where ever I went, including freeway, but if I went to a drive through, it would heat up. I thought it was the coolant switch in the radiator, since my fan worked with the AC.
Started to get the Jeep ready for the winter, and now it heats up right away.
I replaced the fan switch, and the fan still does not work, and I think the fan switch side of the radiator is just staying cold.

So, is it possible that the thermostat is bad, and not opening, and that is restricting the flow? Can a thermostat go bad just sitting around for months?
I just started thinking about it, and I think I will take it apart in the morning.

Any opinions are greatly appreciated......
Thanks,
Bob

Thermostat is just spring loaded... what's your coolant look like? It is possible for it to stick shut. The thermostat may not be bad, just take it out, clean it, and see if that helps.

Jak "do the cheap things first" bob

It's cheap, get a new t-stat that fails open. Maybe you have air in your system.

Thanks for the responses

I did "burp" the system when I replaced the fan switch in the radiator.
I feel much heat in the radiator when I put my hand on it. I just think it's weird that something has changed since the xj has been sitting for while. Maybe just a timing thing..........

I will pick up a thermostat at the local store, As I think O'reily has one with the breather like the factory one.

Thanks,
Bob

Heating up at a drive through sounds like a fan clutch issue to me.

Get a Stant Superstatif they've got one, 195*

Check to see if the top half of the radiator is cold (indicating trapped air in the radiator, due to replacing the E-Fan switch. It is a real pain to get the air of top half of the Renix radiator (once it gets in) due to the screwy inlet hose P-trap effect with a closed T-Stat and the entire layout.

The early warning signs sounded like a bad fan clutch, or bad efan switch.

But it also could be early signs of restricted flow in the radiator.

If the thermostat is bad, closed, the upper hose will be cold as the dash gauge indicates it is overheating!!! (unless it sticks half way open?)