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What is the purpose of this vacuum valve inside air cleaner 1970

Started by Bill Balkie 24172, February 19, 2020, 08:21:40 AM

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Bill Balkie 24172

Hello ,
    Can someone please explain to me the purpose of this vacuum valve inside the air cleaner on a 1970 Cadillac ? And does it need to be replaced periodically . Also what is the proper name of this device .

    Thank you ,
             Bill
Bill Balkie
1970 Coupe DeVille
2009 CTS

hornetball

It's a thermal device that tries to keep the temperature inside the air cleaner at about 105F by mixing air from the cool air snorkel with air from the stove around the driver side exhaust manifold.  It's called a "thermac" air cleaner assembly and is discussed in the emissions control section of the FSM.

Personally, I've disconnected the vacuum to mine as I want the engine injesting the coolest air possible.

MaR

The whole point of the system is to help the engine warm up faster. When the engine is cold, the valve is open and the butterfly valve in the air cleaner snorkel closes to pull air from the shrouded duct over the drivers side exhaust manifold. Once the engine starts to warm up, the valve closes and cuts the vacuum to the butterfly valve.

klinebau

The purpose of the thermac valve system was not for quicker warm-ups, although it does improve cold weather operation.  While much maligned, the system actually served several purposes.  The main reason was to keep a constant temperature for the air entering the carburetor and allowed the carburetor to operate in the air temperature range for which it was designed.  This helped with fuel atomization, prevention of carburetor icing, and emissions.  Many have disabled this system and there is minimal impact to doing so, but I believe the system can actually provide some benefits if operating correctly.
1970 Cadillac Deville Convertible
Detroit, MI

Bill Balkie 24172

Hello,
  Thank you for all the  helpful comments . I am disassembling  my Air cleaner to give it a good cleaning and repainting . i Needed to know the function of that part. I am keeping it stock . I was just courious and it all makes sense .

     Thank You ,
        Bill
Bill Balkie
1970 Coupe DeVille
2009 CTS

Jeff Wilk

My thoughts on all of these various systems and devices that are said to only have marginal benefits are that you need to look at them as the whole system they are part of. If any part only has marginal impact it still is positively affecting other functions and when disabled it can start a slow cascade of less than designed performance and function overall. When at all possible keep it original is my motto when it comes to vintage cars.

"Impossible Only Describes The Degree Of Difficulty" 

Southern New Jersey

1959 Cadillac Fleetwood Sixty Special
1975 Eldorado Convertible (#12 made)
1933 Phaeton Chevrolet - "Baby Cadillac"
1933 Master Sedan Chevrolet - "Baby Cadillac"

SOLD
1976 Cadillac Mirage (factory authorized Pick-Up)
1958 Cadillac Sixty-Special
1958 Cadillac Sixty-Special
1958 Cadillac Sedan
1958 Cadillac Coupe Deville

Bill Balkie 24172



Hello Jeff,
   I feel the same  way . A lot of thought went into the design of that system . If the parts are available why not keep it original .  Even if you don’t understand the system it gives you the opportunity to learn about what the engineers we’re thinking .
.
  Bill
Bill Balkie
1970 Coupe DeVille
2009 CTS

wrench

It’s starts by tossing the thermac valve. Pretty soon you are flipping the lid on the air cleaner.

By that time it’s too late. You are a rebel and wearing a black leather jacket, banging on the jukebox to get it to play Rock Around the Clock for free...
1951 Series 62 Sedan
1969 Eldorado
1970 Eldorado (Triple Black w/power roof)
1958 Apache 3/4 ton 4x4
2005 F250
2014 FLHP
2014 SRX

Scot Minesinger

The reason not to keep it original is if that valve leaks your car will overheat. 

The replacements have proven not durable.  When the valve leaks it allows vacuum to close the snorkle damper and intake air is drawn across the exhaust manifold.  This is for warm up only.  My 1970 Caddy ran hot and this was the cause.  Generally the heat riser stuff is good if you live in MN and drive in the winter.  Our use of these cars is generally not in cold weather.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

cadillacmike68

Quote from: Jeff Wilk on February 19, 2020, 12:34:42 PM
My thoughts on all of these various systems and devices that are said to only have marginal benefits are that you need to look at them as the whole system they are part of. If any part only has marginal impact it still is positively affecting other functions and when disabled it can start a slow cascade of less than designed performance and function overall. When at all possible keep it original is my motto when it comes to vintage cars.


I'm in agreement with the sole exception of the stooopuid AIR pump and its associated nonsense.
Regards,
"Cadillac" Mike

Roger Zimmermann

Quote from: cadillacmike68 on February 22, 2020, 08:45:40 PM

I'm in agreement with the sole exception of the stooopuid AIR pump and its associated nonsense.
I agree! This is why I removed the vanes from the pump installed on my '72 CdV.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101