You have a heater control valve that is in the rear of the engine, and somewhat difficult to access. There is a vacuum line going to it. You need to determine if vacuum is getting to that valve. I am not sure if it needs vacuum to let hot water flow to the core, or if no vacuum allows it to flow. It could also have a faulty diaphragm, and therefore be non-functional.
Tuesday, December 1st, 2009 AT 9:57 PM