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Hummer Knowledge Base

The Hummer Knowledge Base

"Vacuator" or "Flap" Valve

I was working on my truck today. I removed my snorkel, to check the fitting at the base. To my surprise, I found evidence of muddy water in the rubber elbow that connects the snorkel to the air filter. I next, removed the air cleaner, which was full of dried mud! While cleaning out the dusty mess, I found the source of my problem. At the bottom of the air cleaner housing, there is a drain. This drain consists of a rubber boot that is clamped to a metal flange which in turn is attached to the main air filter housing. This flange had broken off the truck. This left a hole in the air filter housing that was letting water and mud in.



Glad to hear your rig escaped injury... I tried to raise this air canister vulnerability issue before but, it seems to get lost in snorkel discussions. Snorkels are moot if the canister flange and flap valve ("duckbill" or "Vacuator valve") aren't functioning properly... (Homey will be swapping the Vacuator valve with my solid rubber cap (from the Military deep fording kit) before I jump into the water at Ft. Hood...)

BTW the cork gasket (rubber on late models?) that is supposed to seal the air intake flange (the mount for the air intake "mushroom" or "hat") is badly deformed on many Hummers (the three bolts and thin air intake flange provide a poor seal for the air box). This allows "bow waves" and rain to enter the top of the air box--which shouldn't contribute to water entering the engine--but does allow water leaking into the air box to come in contact with exposed electrical connectors for HVAC system components...


Good point Bill.

This flap valve keeps muck from getting INTO the air cleaner while letting any water out. My spare diesel air cleaner shows this Vacuator valve on the inlet side of the air cleaner, it should not let air in. The vacuum should close it down. Remember to make sure it is positioned to the lowest point for draining purposes. Should always be checked.

On the gas there is a Vacuator valve on the air collector not the air cleaners proper since there are 2 air cleaners for air volume purposes.

BTW if you want to make a double 90 snorkel, you can put 2 of these tight 4 1/2 90s at the base, so the snorkel is coming out more at the side rather than obstructing your front vision. Donaldson also makes these tight 90 and spare vacuator valves.


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