I noted this past summer I was getting a LOT of heat on the floor outlet of the heater on my 75 Hurst Olds. So come to find out the vacuum hose to the heater control valve is just dangling . There's an (approx.) 1/4" hose coming off the little vacuum valve that controls the hot water, That hose is about 8" long. and flexible..... then that reduces down to kind of a hard plastic much smaller piece of tubing that appears to maybe only has a 1/8" or 1/16" opening. I can't see where that might go? I've read that , without that connected the valve remains open so that would track with the heat coming out even with the control on the dash set to off. I've looked at a couple mechanisms on Ebay and it appears at the rear of the heater control assembly there's short of a "turret" of vacuum lines....so where does the main line going from the control on the dash TO the vacuum valve on the engine? Got any pics to show me? Thanks

 

Short version that vacuum pipe routes back to the HVAC control head. The 1975 CSM shows all the HVAC vacuum routing in the airconditioning section of the manual.

 

is there an easy way to access the connection to the dash control for that?

 

Look on the firewall to see if there’s a broken line sticking out somewhere. Maybe you’ll get lucky.

 

OK, I'll do that first.

 

I’m just now looking at your picture on a larger screen and the upper portion of the plastic line looks ragged. Is it cracked or crumbling? If so, that may be the issue. It could be replaced with a piece of nylon oil pressure tubing if it’s bad.

 

I'm not sure if that smaller hard plastic line I'm holding onto is even correct. The black line coming off the vacuum control valve is a cloth covered line then it reduces down to that very small hard plastic tubing I'm holding onto. I can't see anywhere on the firewall that a line broke off or an opening for the vacuum line to run to? There is a small hole going through the firewall in that area, and I tried poking that hard plastic piece of tubing I'm holding onto through it, to see if that was the routing for that tube, but there did not seem to be an opening other than about a a 1/2" into the hole. so I doubt that this is the route the tubing would take?! I've attached another couple pics. I amost can't believe that the small yellowish covered hard tubing is supposed to be connected anywhee. The ID isn't more than a 1/16" inch and if it's disconnected from something, in all liklihood it's broken off of it as it would not flex enough to insert over any sort of nipple. The hole through the firewall is best seen in the 2nd pic on this response.

 

One of my vehicles had hard plastic vacuum lines from the factory. If one cracked, a rubber hose could be used to splice it back together.

The heater valve vacuum line goes through the one of the holes in the firewall. I do not know which one on your year vehicle.

 

were they VERY small diameter both OD and ID. I'd say the OD on this hard plastic line is 1/8: and the ID is maybe 1/16". It would have to almost be a molded connection to the control IF that's the line that comes off the heater control lever mechanism. ?

 

Most hard plastic vacuum lines have rubber connectors at each end.

 

I'll keep looking for the connection for that hard plastic line.!

 

Can I just "T" off a vacuum line to close that valve to close it. I only run the car in summer so I don't need heat!