I went and took pics of the spring and washer in place:
The spring and washer have nothing to do with the bypass function because the bypass function is a spring and valve
inside the bolt.
It occurred to me then to have a look what would happen if the spring and washer weren't in there like I've read about some guys not having. The washer in particular gets lost from being thrown away with the filter because it sticks to the filter.
In this picture, the red arrows show 2 holes, there are 2 more holes in line on the other side making 4 holes total in that line.
The blue arrow shows 1 hole, there is another on the other side of the bolt making 2 holes on this line.
I took careful measurements of the bolt, housing, filter, and how it all sits on the front engine when it's together.
It's hard to see in this picture but if the spring isn't in place then the rubber seal on the filter
could block the 4 inline holes, allowing oil to pass through ONLY 2 holes.
I say
could because it would depend on where the cartridge is sitting on the bolt because without the spring, the cartridge is free to move forward or back on the bolt.
incidentally, the washer makes VERY little difference in where the filter sits and it has
nothing to do with the pressure bypass, neither does the spring.
Back to the bypass valve......
I put a air nozzle on one of the holes (on the bolt head end, the bypass holes) and covered the others with my fingers and found the bypass will open at about 20 lbs pressure and is sealed air tight below that pressure.
This is
differential pressure. Meaning the pressure would have to be 20 lbs higher
outside the filter than
inside the filter.
I don't know what this equates to in real use. Could only guess that there is rarely 20 lb.+ difference unless the filter is badly clogged.
By taking a close look at the entire assembly I have found:
1. The filter spring is important. It keeps the oil supply holes feeding the oil to the engine fully open.
2. The washer......not important. It simply serves as a "seat" for the spring against the filter cartridge seal.
3. Neither the washer nor spring have
anything to do with bypass. Bypass is done by a valve and spring
inside the bolt.
4. There is NO part in this assembly to prevent oil from draining out of the filter when the engine is off. When I pulled the cover, about 1/2 the filter housings worth drained out.
Maybe something more will come to me but I still cannot see how any kind of malfunction in any of these parts (except a clogged filter) could cause engine knocking noises.
