First of all, hello and thank you for your time.

A couple of days ago I noticed that my '06 Jeep Cherokee was leaking a significant amount of coolant. To my surprise it turned out that the radiator had cracked at the corner near the top hose input and was guching coolant.

I decided to replace it completely, the process went as smooth as it could, no issues arose and I even changed the Thermostat since its rubber ring was starting to crack.

After refilling the coolant and letting it run for an hour I noted there were no leaks and the temperature was perfect. However today, the day after the replacement, while on the road the temperature began climbing steadily. Before it got near any dangerous temperatures I pulled over and checked for leaks or anything. Nothing, coolant level was fine and there was no drips. I did however notice that the radiator output hose was colder than what I remembered it to be after running the test yesterday.

Any ideas? Could it be that the new thermostat is jammed?

Thank you for your time.
Have a good one.

 

Could be stuck thermostat. Could also be a blockage or air bubble. I've had other cars in the past that wouldn't prime if the water pump went dry. Had to pour coolant down the closest hose to get the pump filled and primed again. Take the hose loose at the thermostat and see if you have coolant there. If it's dry, you've got no circulation. Also, check your coolant level again. You may need to top it off two or three times to get the system full. It can look full, then the thermostat opens and sucks a ton into the dry engine and suddenly you're way low again.

 

sounds like air in the system for sure

 

I always drill a 1/16" dia hole in the thermostat prior to install, on the flat ring area just above the spring cage. This allows a very small bleed, won't affect the thermo operation but allows any trapped air to "burp" out of the block for full fluid fill.