What is this air cleaner check valve in the vacuum hose coming off the vacuum motor on the air cleaner snorkel used for?

 

I would need a part number or a picture of what you are talking about to be absolutely sure what you are describing.

However it sounds like you are talking about either the AC/BI-MET (Air cleaner/Bi-metalic) vacuum control valve, or a TVS, (Thermal Vacuum Switch).

The main reason for these switches is to let vacuum through to the vacuum motor to close the "snorkel door" to the heated air tube that goes to the exaust manifold when the truck is cold, helping the engine warm up, or stay warm in cold climates.

When the engine heats up, the switches sense the temperature and reduce the amount of vacuum leading to the vacuum motor, therefore it starts to open the "snorkel door" to cold air from the front of the truck. It will blend the heated air and the cold air regulating the air intake temps. If the air is very cold outside the "snorkel door" never fully opens up. If the air is warm outside, the vacuum switches will fully shut off the vacuum to the vacuum motor, letting the "Snorkel Door" fully open up, shutting off the heated air, and letting full outside air through to the carb.

Hope this explains it.

 

Thanks for that thorough description! however I was talking about a colored check valve or delay valve that is in the hose itself.

Like this:

80-86 Ford Air Filter Housing Bronco F150 F250 F350 OEM - eBay (item 250603429359 end time Mar-19-11 12:15:06 PDT)

FORD AIR CLEANER SNORKLE - eBay (item 230566949366 end time Feb-23-11 08:39:38 PST)

 

It's most likely a delay valve. It keeps the vacuum signal from changing abruptly.

I do not think it is, or see a need for a check valve, as vacuum goes only one way from the vacuum motor, toward the engine, and if it wasn't able to bleed off, the motor would be open or closed all the time.

I would need a part or engineering number to get any closer than that.

 

Why would the vacuum motor in the air cleaner snorkel need a delay valve? I know the older air cleaners didn't use it.

 

That's a good question.

I was just at the wrecking yard after our last posts and saw one inline like was pictured. The emissions lable says it is a delay valve.

My only guess would be to keep the door from opening or closing suddenly when you excelerate or decelerate quickly. It may also help prevent the vacuum motor from ripping.

The emissions lable states what it is, not why it is, unfortunately.

 

Does anyone have a schematic on how the hoses run to this valve and the snorkel? Thanks