What the devil is it ?

[Reg Evans]

There is a 41 Plymouth for sale on eBay right now and the engine has what looks like a vacuum operated diaphram on top of the water pump fitting.

What the heck is it ?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=250567743817&viewitem=&sspagename=ADME%3AB%3ASS%3AUS%3A1123

[Merle Coggins]

Must be some sort of vaccum operated heater valve.

[moose]

Looks like the valve I had on my '70 Buick. When the heater was off, it shut the water to the heater core off. That car used a vacuum controlled HVAC system, and was always having problems. I don't know why anybody would want to put something like that in...

[BobT-47P15]

That's an awfully small diameter line - compared to the hose usually

found.

[Cpt.Fred]

there it is again.... "rat rod"

they never learn

[Reg Evans]

That's an awfully small diameter line - compared to the hose usually

found.

There is a normal sized heater hose right under the vacuum line. I just don't understand why the owner thought a vacuum operated valve would be needed there.

[Tony Cipponeri]

I have one on my car, it came with the Vintage Air heater I bought from them. Tony C

[48mirage]

It appears to be even more complicated. If you look at the 2nd picture there is a line from the air cleaner into the passenger compartment. Is this his vacuum source for operating the diaphragm? I'm guessing there is also a switch inside that he can shut it off with.