Join Date: Jul 2010
Location: The Mojave Desert - Palmdale, Ca. U.S.A.
First, confirm your WP is turning the correct rotation for your engine. IF your Jeep uses a serpintine belt, the WP is a reverse-rotation WP.
Also make sure the T'stat is facing the correct way.
Open the heater control valve also while run'n the engine.
You have air trapped.
Did you replace the cap??