What should I use to block off heater core hoses?

[efficient]

That is a bad idea. The heater supply is from the back of the head and the return is to the inlet of water pump. If you loop the hoses the coolant flowing through the hoses will not go through the radiator and the engine may run hot. When the heater is in use the heater core becomes a mini radiator and when the heater isn't being used the valve blocks flow through that loop.

gonna bump this up and agree with you that it does make the car run hotter. i looped my hoses together and makes my car run hot even on the freeway. usually my temp needled would be in the middle when I'm in traffic now that it is looped, my temp never stays at the 11'oclock position just in the middle.

[dnguyen1963]

That is a bad idea. The heater supply is from the back of the head and the return is to the inlet of water pump. If you loop the hoses the coolant flowing through the hoses will not go through the radiator and the engine may run hot. When the heater is in use the heater core becomes a mini radiator and when the heater isn't being used the valve blocks flow through that loop.

Jim - correct me if I am wrong. The coolant DOES NOT enter the heater core until one turns the heat on, correct? If that is true then looping the hoses should not cause any problem. I agree that fixing the problem, not bandaging it, is the best solution here.

[efficient]

I'm going to be fixing the heater core. i don't want my car running hotter then before.