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Heater Valves (For All AMCs)

When you look for heater valves for your AMC or Jeep there are two types. There is the basic inline and there is a bypass valve.

For most vehicles before 1982 and all after a bypass valve was specified. While the inline valves are cheap and plentiful, I would recommend everyone with a 4 or 6-cylinder either use the bypass valve or eliminate the valve entirely.

The reason that AMC used the bypass valve is that the inline 6, unlike the V8 has no bulit-in bypass for the cooling system. Without a way for coolant to flow before the thermostat opens the head will heat much faster then the block. This causes problems with head gaskets, with thermostat cycling, and creates excess wear on both the head and the piston bores. I believe it was also one of the causes of the need to re-torque the head on the old 195.6 engines.

All AMC heater control valves are normally open (they allow water to the heater core) and close with vacuum applied. I have found 4 styles available, two specified with a six, the only difference is the bend in one of the nipples, and one for the AMC 150 that has several bends. These three are generally priced at $80-$100.

The forth style is specified for Jeep Cherokees through 1998 and is plastic, after that Chrysler simply dropped the part and allowed the heater core to remain in the loop at all times. The plastic part does age faster, and there are common complaints of it weeping from the valve, but the big advantage is that it is available for under $20 at any parts store.

The disadvantage of eliminating the valve is that it adds some to cabin heat, but it is certainly an almost free fix.

These valves are all interchangeable, part numbers to come.

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    Response: Inline Valves

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