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Re: Again with Filters?!
> On drain back valves..check valves..or whatever.
> 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)?
... do I even care about this thread anymore? ... I guess enough for one
last response ...
Let me see if I can come up with an analogy for your argument ...
Assume that you have a glass of water and two straws. One straw is com-
pletely open and the other has a one-way valve that allows water to be
drawn up the straw, but not flow back into the glass. Assume that you
have a faucet that keeps the glass full at all times. If you draw water
from the glass using either straw, the faucet will tend to keep the
If you stop drawing water and open the end of the open straw, water will
flow back into the glass and the glass will be full with the straw drain-
ing to the point that the water level is even with that in the glass (and
any extra water will overflow the glass). [I'm ignoring any capillary
If you repeat the test with the straw with the valve in it you will find
the glass is still full of water at the end of the test, but the straw
remains full of water as well ...
The major effect that is not modeled in my analogy is the fact that there
is a seal between the straw and the glass, and any backflow (overflow)
goes back into the faucet.
May I suggest a more appropriate version of your test would be to shut
off the engine and wait a while (a few hours?) before removing the filter.
Capture the amount of oil that overflows when the filter is loosened and
compare the volume released in each example. I would expect that you
would notice that more oil would be captured for the filter with the valve
than for the filter that had none. The oil is staying in the oil passages,
meaning that the next time you start the car the pump has to pump less oil
in order to pressurize the system and get all of those cam and crank bear-
ings floating as they should be. Audi states that this valve also helps
to minimize the amount of noise that the lifters make after the car is
started after sitting for a while ...
If you are not convinced of the value of the anti-drainback valve, then
don't make it a requirement of the replacement filters you buy and be done
with it ...
San Jose, CA (USA)