Why would an air filter have a hose connection on it?

[Murv]

I'm assuming this is the original air filter anyway, found it under the seat.
The engine has nothing on it currently, it pulls the air directly into the turbo which I assume is not a great idea.
The filter has a large hose connection fitted to it, what would that be for?

It also has a hole on the rear of it, any idea why it may be there?

Plan was to blank both of them off, or, fit a hose and another air filter at the end of it to allow more air through but I can't see any reason for the hose fitting so assume it must serve some purpose?

Engine is a 2.5 turbo diesel.

 

[David2452]

Could be some kind of closed crankcase ventilation hose tail I guess, but engines are not really my thing so probably not.

 

[oceanpilgrim]

that was proberly for a vent for the rocker cover,ie to suck out the venting gasses from the top of the engine it then gets sucked it to the engine and burnt,goes out of exhoust
but that air cleaner is to small for a turbo engine any way,turbo's can blow but not suck will just cause a depression over the inlet,needs to be at least three times longer,dia is just ok
may also have at sume time been run on gas with a gas conversion
graeme

 

[reeac]

I would support rocker box vent suggestion. Does the rocker box have such an outlet on it of same diameter as the hose connection?

 

[Murv]

Thanks all, I don't know if there is an outlet on the rocker box, I don't think so, but will check later.
It does look small to me although the filter material is a fairly crude fibre material that is very free flowing (took it out and cleaned it yesterday.) Could that be why the last owner removed it, it could have been robbing performance?

 

[Steve Clayton]

Could be some kind of closed crankcase ventilation hose tail I guess, but engines are not really my thing so probably not.

+1; I'd go with that. Look for a small hole, possibly with a rubber grommet to support a push fit, somewhere just above the crankcase.

 

[wotayottie]

thats an old style petrol car air filter - maybe your boat has a converted car engine. anyway to reduce hydrocarbon emissions cars have to ingest their own oil fumes so there is a pipe from the rocker box to the air cleaner. there will be a corresponding spigot in the rocker box. best reconnect it - you dont want oil fumes in the cabin.

 

[earlybird]

I'd also guess that it's for rocker/crankcase fumes, though it looks a bit oversized.
The purpose of the other hole, also a guess, might be to prevent collapse and ingestion of bits of the filter element if it got heavily blocked, but rather negates the purpose of the fiter.

 

[rob2]

The assembly looks just like the pancake filter I fitted many years ago to a Webber downdraught carb (on a mini). It had a foam element which could be washed out and lightly oiled to improve its dust trapping ability. The hose tail looks to have been added either by a previous owner or the engine manufacturer. As other have said, you need to seek out any breathers and make sure they're attached.

Rob.

 

[Murv]

Many thanks all, seems that's what it is

Not clear from the picture, but that large hose that leads from the oil filler cap is about a metre long and trails into the bottom of the bilges so I imagine that is where it originally connected.
I'm going to plug the small hole with a nut and bolt and reconnect the breather.
That's one mystery solved!