Heater control valve replacement
 

Has anyone replaced the heater control valve in their 951? The heat stopped working and it is not the flap door clip being broken, that looks fine. The HCV looks pretty buried beneath a number of vacuum lines. Is this a procedure requiring the intake manifold being removed in order to get better access? Thanks for any help.

It might not be absolutely required to remove the intake, but it's definitely going to make it easier. Removing the intake is pretty easy anyway, and it'll give you a chance to replace any old vacuum lines too. I'm not sure how likely the HCV is as the cause of the heat not working, but it's worth replacing it anyway because they have a tendency to break and dump coolant into the clutch housing.

It's doable without removing the intake, but like many tasks on this car it's an exercise in contorshinsome....made up word?

Before replacing it, try manually opening the valve and make sure you get heat, and/or put a vacuum pump on the valve and see if the valve opens/closes. It's not a terrible project, but enough of a hassle that you don't want to do it unless you're sure the valve is bad. I'd remove the intake for sure if you end up replacing it.

OK, thanks for the advice, I think I can do this. Will probably pull the intake. I don't know how people have got at the HCV with all the electrical and vacuum lines in the way, and were able to unscrew the hoses, without taking the intake off.

I did it without pulling the intake. I also replaced the plastic valve with a metal one. If you search on the forum you'll find the part #. I also replaced the hoses with some slightly different ones to relocate the valve away from the inspection hole on top of the bell housing. Coolant errantly going down into that whole might not be a good thing...

mtnman82 - that is a great idea to relocate it away from the bell housing. I'll look at doing the same. Did you go with the metal vacuum housing because of better reliability?

Thanks for the photos. The top picture is open, I guess, since the black arm is extended, not being sucked in by the vacuum, right? So the valve/diaphragm are open and supplying heat through the heater core when there is no vacuum, I take it.

Yes, the top photo shows open; that's the default position of the black arm (it's spring loaded and rests "open"). I'm assuming the vacuum pulls the arm (bottom photo) which closes the valve.

On my car, when the engine isn't running and I peek at this thing, it's always in the "open" position (top photo), regardless of setting on the interior HVAC control temp. Therefore, since it rests in the open position (full heat), I assume the instruction to turn the temp knob to full heat when, say, draining/filling coolant, is not necessary.

And, I'm assuming when you turn the control towards Cool temperature, engine running, the vacuum pulls the lever to close the flow of hot coolant. Of course, I've never really observed this in action, just going by deductive reasoning. Like most things on this car lol

FYI it must be a pretty strong vacuum; that spring loading is quite stiff, requiring some force to move. I couldn't get the arm to move by sucking on the vacuum nipple. Um, maybe I shouldn't mention this experiment :icon501: