[bestgenman]

Ben and Rob, you both are on the right track.  The PT sets are hard to get the air out of the system.  The ideal fix is to insert a fitting at the highest point with a petcock to allow venting.  This eliminates having to remove the thermostat housing or remove hoses.  You may have to have a tube fabricated for the 1-1/2" hose (or whatever your hose size is) with a port for the petcock.  If you don't have the capability, then Newell or a radiator shop will make one for you.  It just saves down time when you are out on the road and this happens.