spenmasc,

Go here:

https://www.cherokeeforum.com/f2/hea...utside-180810/

 

I've had this issue a few time with various vehicles after cooling system replacements/engine swaps etc. The thing that has worked for me every time is to burp the system.

1. Make sure the vehicle is cool
2. Jack up the front of the vehicle or park it on a hill front end up
3. remove radiator cap
4. run vehicle until it hits operating temp
5. squeeze radiator hoses to work out possible bubbles/airlock while running.
6. keep a close eye on fluid levels
7. repeat until you have warm air.

I really hope that this is what it is. Good luck!

Aaron