I would like to know, how is that Heat riser valve supposed to work?

What position it should be at cold/warm engine?

Is that spring bi-metallic?

Joug

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Sorry, my english is not very good

Joug:

There are two different kinds of heat riser valves.

Engines through 1970 used a heat riser that had a rectangular counterweight of approximately 25mm x 35mm. With the engine cold and stopped, this counterweight should be approximately horizontal. If you are standing at the left side of the car, put your finger on the top outboard corner of the counterweight and push. You should easily be able to rotate the valve counterclockwise approximately 90° so the counterweight is approximately vertical. When you let go, it should spring back to its original position. With the engine fully warmed up, the counterweight should move on its own to the vertical position and stay there until the engine cools back down.

Engines after 1970 used a heat riser that had a round counterweight of approximately 45mm diameter. With the engine cold and stopped, you should be able to rotate this counterweight approximately 90 degrees counterclockwise, and when you let go, it should spring back to its original position. Many of these valves do not shift permanently to the "heat off" position when the engine is hot; at idle they remain in the "heat on" position, though they are held there less strongly when the engine is hot.

Yes, the spring in both kinds of valve is bimetallic and thermostatic.

If you cannot freely and easily move the valve, it needs to be cleaned and lubricated. The very best stuff for doing this is Mopar Manifold Heat Control Valve Solvent, but I do not know if you'd be able to find that product at a Chrysler dealer in Finland. It is far, far, far more effective than ordinary penetrating oil for this task, nothing else even comes close.

If even this solvent cannot free up your valve, you will need to replace it. The parts are still available from Chrysler.

Thanks Dan

My engine is 78 model and it's heat riser valve is working ok I think. In cold engine it is possible to turn 90 degrees counterclockwise and it's turning back when releasing it. When engine is hot and idling, the valve is about in same position, but there is not so much spring tension, than in cold engine.

Joug

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Sorry, my english is not very good