This started about 3 years ago. Very little heat coming from the heater. Last year I installed a new fan clutch (old one was stuck and did not turn off), replaced hoses, radiator, and thermostat (3 times), flushed the the cooling system. I still have very little heat, and still have a gargling noise (sounds like from under the pass side dash) from time to time. If heater and or defrost or air is on long enough I will get a pounding noise as if someone is under the hood pounding away until I turn it off. Gage inside has NORMAL written on it and if heater, defrost, or air is on it will sit at cool and the climb between the M and A and the needle will fly back down to C and it will never overheat. If the heater, defrost, or air is not on the gage stays at C. Coolant is fine and hoses are hot. I'm getting tired of the cold car, and don't want to get rid of the van, it still runs good other wise. Hope you can help.