Function of BMW p/n: 13711274704

[demos]

I have this green thing in the air filter housing. According to BMW ETK they call it 'voltage regulator' which is mind boggling since there are no wires connected to it. It just has 2 vacuum hoses.



It's item number 6 here:
https://www.realoem.com/bmw/enUS/showpa ... Id=13_0601

Anybody know the function of this thing? How to check if it's working?

[Jeroen]

Clearly not a voltage regulator, but a vacuum valve instead. I believe it's supposed to limit the air flow. Never ever bothered to investigate its purpose or functionality, but I never ran into any issues with carburettors that made me dig that deep haha

[Peter V.]

This is a wax operated vacuumvalve. This opens and closes the valve in the airfilterunit to get fresh air during warm temperature and preheated air (exhaustmanifold) during colder temperature.

[demos]

Valuable info thanks Peter!

How can I test its functionality though? It seems blocked when I blow into it.
I doubt it's functional since 1981. Is it worth replacing?

[Peter V.]

Valuable info thanks Peter!

How can I test its functionality though? It seems blocked when I blow into it.
I doubt it's functional since 1981. Is it worth replacing?

That depends on the position of the valve in the airfilterunit.
When it is open in the direction of the fresh air I would not make a big trouble out of it.

Maybe if you place the part in the refrigiator and test it it could be in open connection.