Truck Repair: cummins L10 9000 interigal head, antifreeze coolant, air pockets

Question
why won't the antifreeze coolant flow to the heater core?

Answer
Hi Jacob,
some times there gets to be air pockets in the high spots in the system, also there could be coolant taps installed to restrict flow to the heater core for summer. try slowly removing the upper hose off the heater core and see if there is air at the top. also check the hoses to see if they are spongy or swollen causing a restriction. Some trucks have a shut off valve for the heatercore which is actuated by a cable from the cab dash controls, if this is stuck closed or has plugged up internaly there would be no flow. run the engine up to temp. and feel both lines going to the heater core...they should be even temperatures...if you feel along the hose and you find a spot that is cold obviously there is a restriction there.

Good luck,

Matt