Warm air thermostat

[Dave105]

My warm air thermostat (the one that sits in the right air horn and operates the warm air flap which sucks air from around the exhaust)was broke so got another one.
My problem is which pipe connects from the vac pipe and which goes to the warm air vac diaphragm?



the brass pipe holds vac when sucked the other black plastic one doesn't.

Im guessing connect the brass one to the vack side and the black one to the heater diaphragm.

can any one confirm this?

why does the black pipe not hold vack? will this not cause a vac leak when the valve is open?

any advice appreciated.

[Manfred]

What year and model is this for?

[Dave105]

Hi
The engine is a 2L CJ but the carb (PDSIT) set up and the oil bath air filter are off my origional 1972 1.7L CA engine.
Think its a one year only airfilter but I think that the later paper filter air filter boxes have the same air horns (AKA piza slices?)
My origional thermostat doesent hold vac on either pipe put the two replacments I got this weekend both hold vac (suck!) on the brass bipe but NOT on the black plastic one.

[Oregon72]

Dave, The left brass nipple (closest to driver's side of car) is connected to the right brake booster elbow. The right nipple goes to the preheater diaphragm.

[Dave105]

Connected it all up over the weekend:

brass pipe to vac take off
plastic pipe to warm air diaphragm

Anyone know at what temperature the valve is ment to open/close so I can check its all working.

Thanks

[Amskeptic]

Connected it all up over the weekend:

brass pipe to vac take off
plastic pipe to warm air diaphragm

Anyone know at what temperature the valve is ment to open/close so I can check its all working.

Thanks

58*-60* on up incoming air temp should open vacuum valve to that weird reed sound.

As I remember it (and my memory is slowly failing in the 38 days since I last saw my bus), the inboard side (black plastic) of the thermostatic vacuum valve goes to the source vacuum ('72 right booster elbow, '73 off the center vacuum nipple on the central idling circuit distributor), and the outboard (brass) goes to the flapper diaphragm. If the photograph in this thread has the brass on the inboard side, I can only imagine that the valve can go in the pizza slice either way. The important thing here is to test correctly:
With a cold valve, you should be able to create a vacuum through the valve while listening for the flapper to move up inside the preheater. When hot, you should not be able to pull a vacuum. The valve bleeds with a weird little moan when refusing to open the preheater door.
Colin