how do I tell that there's a bypass valve?

[metroplex]

How do I tell a filter has a bypass valve?

 

[metroplex]

or rather anti-drain back valve.

 

[Al]

Look at the little holes. They are the inlet to the filter. When the oil pump stops pumping, the oil tries to run back out those holes (away from the filter). If you can see rubber in those holes - that's the antidrainback valve. You can take a ballpoint pen (with the point retracted) and push slightly on it and you will see it's rubber. I'm not sure any filters are made anymore without an anti-drainback valve.

 

[Patman]

The specified filters (and the longer one) for my LT1 Firebird, and for the LS1 cars don't have antidrainback valves. This includes the AC Delco PF25, PF35, PF44 and PF58. The PF35 also has a twin, the PF1218, which does have the antidrainback valve though. Also, the PF58 has a twin in the PF59, which has the antidrainback.

These filters also have no bypass valve, since it's built into the block on these GM cars.

[ September 23, 2002, 11:10 AM: Message edited by: Patman ]

 

[Chris A]

quote:

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Originally posted by Patman:
Also, the PF58 has a twin in the PF59, which has the antidrainback.

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Ahh, I wondered what was the difference between those two. Thanks.

 

[metroplex]

so if I see a neoprene/rubber "flap" inside of the holes on the filter inlet, it has a anti-drain back valve?