Hi, I am John Mc, a Ford dealer technician.
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Is this a 3.0 ohv engine or dohc. If it is a dohc it will say so on the fender badge.

It is very common on these cars for two things to happen. First is for the fins on the water pump to rust off. I will still have enough flow to keep the engine cool but not enough to circulate water through the heater core. The second thing is for the heater core to stop up with sediment. Water will still flow through part of the core but not enough to produce heat. These engines are bad about cooling system problems. When you are done with your repair make sure to thoroughly flush the system. When refilling the system use green coolant and distilled water mixed 50 50.

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Thanks,

John Mc

If you still have follow ups please ask and I will be glad to assist.