Bobcat 763 air cleaner pressurization

[Fred Bryant]

I have got a, new to me, bobcat 763. I just got it running and noticed that the air cleaner 'can' is pressurized. That is, since the cover has been dented, I can feel a little air blow out of it when the machine is running. When I turn off the machine, there is a big burp of air ( not a backfire ). I would expect that the air cleaner 'can' to be under a slight vacuume all the time as the machine is naturally aspirated. It seems to be under a bit of positive pressure. Is this normal?

Thx's, Fred.

[SSdoxie]

It doesn't sound normal but I don't have any idea what could cause it. How does the engine run? Any smoking present?

[Fred Bryant]

The engine is definitely pressurizing the air cleaner. The engine is running well, no smoking. It does seem to be related to engine RPM. From idle to full, the pressure pulses increase in frequency. One can feel the pulses through the split rubber capped tube on the bottom of the air cleaner. Everything seems to run fine, so maybe it is normal. Can someone give theirs a check?

Thx's, Fred.

[Fred Bryant]

Well, posting a video was a little more involved than I thought, but here it is:

BobCatAirCleanerProblem - YouTube

Any new/more thoughts? Thx's, Fred.

[SSdoxie]

Well, posting a video was a little more involved than I thought, but here it is:

BobCatAirCleanerProblem - YouTube

Any new/more thoughts? Thx's, Fred.

That is the way it is supposed to work. When you first posted, I wasn't foloowing what you were describing.
That rubber "duck bill" is a dirt dump. When the air enters the filter housing it swirls around the fins on the air filter causing some of the dirt to fall to bottom rear of the housing. With each intake stroke of the engine air is drawn in, but when the intake valve closes the air flow is momentarily stopped until the next valve opens. This stopping of fast moving air causes the rubber slit to open and dump some of the dirt out. Theory is dump some of the dust, dirt before it gets trapped in the filter. If the rubber gets deformed or falls off the air filter will still function but you will have to change filters more often,