The heater hoses on my 81' run from the water pump / etc. along the right fender and into a component (water control valve, maybe?), before going in to the heater coil. On the top of this thing there are two small vacuum connections. One runs back to and through the fire wall to the climate control switch I presume. Any idea where the other is suppose to connect? Mine is missing. I have an 81' shop manual but it doesn't appear to mention this. Thanks guys.

Don't know where the other one would go but this valve and/or the vacuum that controls it seems to be a common problem.  On the Carson City trip, I capped off the heater hose connections at the block to avoid residual heat from the heater core.  My plan is to install manual valves in both hoses so I have heat when I need and no heat when I don't.

 I'm with you there. Actually, I was getting ready to install manual valves when I noticed the missing vacuum line. Since I'm not overly concerned with keeping everything original, I don't know why one couldn't just take the water valve switch off when installing  the more positive manual valve.

That's what I did - I just put in a manual valve and it works out just fine.

Both part numbers from NAPA are somewhere in a post by me...

 Founded them

   660-1414
   660-1413

 Worth every dime.
JimG2007-08-04 13:24:02

Ace is correct. If you don't put valves on both hoses you will not get the best results. The heater core will still het extremely hot with only one valve.

Scott ranger32007-08-04 17:56:06

Oh well, so much for the 2nd vacuum line. Both manual valves are installed and working fine. I'm still curious about that second vacuum connection though. Thanks alot guys, I appreciate the in put.