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Re:filter check valves; min. audi content
-- [ From: human * EMC.Ver #2.5.02 ] --
It's because the pump pumps oil "up" through the filter into the engine
galleries whence it runs back into the sump. When the pump is "off" the oil
can drain back, through the filter, in a reversed direction. Two faults
here, one the filtered crud gets washed back into sump, two the galleries
get drained. Both not necessarily fatal but it's a nice thought that the
engine might have some oil up in it when you start it hot, also nice to
think pump only ever has to pump the crud into the filter once. The filter
is still full of oil because it isn't siphoned empty. But it's not the oil
that was in it when the engine stopped, it's the oil that drained back down
to it, pushing out the oil that was in it backwards through the media.
Am I right, guys? Did I ever care before? Am I now pickier about oil
maybe, no, & YES!
PS the only filter I ever took apart I did with a little "unintended off
roading" which cost me an engine. I'll show it to you when you come by,
Paul! I can laugh about it now....
-------- REPLY, Original message follows --------
Paul Royal asked again re check valves.....
1. I asked if these were indeed really useful on a filter that is mounted
exactly vertical...hole side up...no one can seem to tell me, but lots of
listers have claimed it's important. If oil does indeed drain back into the
engine/pan from the filter after shutdown...how come my filters are jam
packed (that's full) of oil when I remove them (even "valveless" FRAMS)?