did 65 mustangs come with an overflow tank. i always see pictures of a hose coming out of the radiator but it looks like it's going to a fomoco bag which is a windshield washer bag isn't it?

 

the hose would have just run down the side of the radiator to the ground. No overflow tanks back then.

 

Yeah, the bag isa washer bag. However, Ford did sell an overflow tank over the counter. Lacking one of those, you can get a generic plastic tank at Napa to mount to the fender, or a nice stainless deal from a Mustang wherehouse that mounts to the side of the radiator

 

yes your car doesnt have one its best to add one they help alot.

 

You also need to change your radiator can to one that is designed for coolant recovery.