mid production changes. the one with vacuum controlled valve emulates the discovery 1, thus technically it shuts down the heat completely. it never works as designed.
the first picture is what all range rovers had ran until the re-design.

 

Both of those RR classics are mine. The one with the valve is being restored, the other one is a parts car. Is the valve system a better system? Am I going to have problems with it? Should I convert it back to the old system without the valve. Not sure how the valve works.

Thanks

 

I recently replaced a 24yo valve in my 1995 LWB. Every now and then it would seep a drip, but never really leaked (not bad for being that old). I replaced it with a new genuine valve and thew the old one in the on-board spares kit.

 

What does the valve do that is better than the original design?

 

The cooling water system is designed to circulate water within the engine before the thermostat opens, this way the engine heats up quickly which is better for the engine and emissions.

The internal circulation happens from the back of the pump. This is also where the heater core connects to. In addition the airflow through the heater core is controlled with a flap so the core is always 'hot'. So the heater core gets cooling water circulation as soon as you start the engine. In cold weather this is nice for the occupants, but obviously slows down the heating of the engine.

I presume the 'new' valve design lets the car control if 'precious' hot water should flow to the core or instead prefer to keep it in internal circulation. More complexity probably driven by emissions regulations rather than technical benefit. Certainly if I was to live in a cold climate I would prefer to get my warm air asap.

 

in my experience the valve (which i refer to as the "artificial heart") was not the culprit, it was the blue electric resistor on pic #3. Basically, its an overly complex system. Manual control levers to operate an electric switch to allow vacuum in the "artificial heart". If you feel that the lower vents kick out heat, when you have the AC engaged, my experience showed a bad electric blue switch. They seem to be NLA, and i was able to source a used one from a D1. To your question - what does it do differently? Not sure... minor change to add more pieces to the puzzle.