Oil Filter Anti Drain Back Valve - how it works

[johnbright]

Tempest Tech Tip 1113 re anti-drain-back valve how it works. It doesn't keep the filter full of oil; it's there to keep the pump full of oil for hot starts.

Highlighting in the PDF is mine.

 

[lr172]

One more reason to use an auto type oil filter.

 

[rv8ch]

One more reason to use an auto type oil filter.

Is there a difference between the anti-drainback valves on an aviation filter and an auto filter?

 

[lr172]

Is there a difference between the anti-drainback valves on an aviation filter and an auto filter?

I always assumed they were the same, but the post above shows that may not be the case, at least for tempest, which I assume is a copy of champion. Auto filters, to the best of my knowledge, use the ADBV to keep oil in the filter vs draining back through the system. This is logical to assist in getting flow as quickly as possible after start up. I have pulled a lot of auto filters in my day and all came out filled with oil, including those horizontal and upside down. Have only pulled a few aviation filters and don't recall whether they were full. I don't use them on planes. Have a vague recollection of pulling a couple and being surprised they didn't pour out oil, but just not sure.

Don't think anyone has done more research on these filters than Dan. Maybe he can chime in.

 

[N10KE]

I always assumed they were the same, but the post above shows that may not be the case, at least for tempest, which I assume is a copy of champion. Auto filters, to the best of my knowledge, use the ADBV to keep oil in the filter vs draining back through the system. This is logical to assist in getting flow as quickly as possible after start up. I have pulled a lot of auto filters in my day and all came out filled with oil, including those horizontal and upside down. Have only pulled a few aviation filters and don't recall whether they were full. I don't use them on planes. Have a vague recollection of pulling a couple and being surprised they didn't pour out oil, but just not sure.

Don't think anyone has done more research on these filters than Dan. Maybe he can chime in.

If you wait long enough (like a day or more), I think you will find that most of the oil will drain back out of the filter. I assume it is permeating from the dirty side through the pleats and out the exit hole back into the sump. I have done this on our RV-7A with a 90 degree adapter, as well as two automotive applications where the filters were upside down. All of the filters were empty after waiting at least one day.

 

[Narwhal]

Good article. It’s interesting to think of the ADBV in the context of the debate about whether or not to pre-fill a filter with oil. The article seems to imply that it wouldn’t matter much.

The Champion filters have an ADBV that functions similarly to an automotive ADBV. The black gaskets pictured below (I believe made of nitrile rubber) are the ADBV of a Champion 48108-1. It has 2 pieces instead of 1 like most automotive filters, as you can see in picture #3.

The orange auto filter ADBVs (Carquest 85515 & STP S8AXL) pictured here are made of silicone. I don’t think that makes a huge difference. Both the Champion or the Carquest filter will hold oil for several days when inverted. You can punch holes in the dome of either filter to let the oil drain out for a cleaner filter change, or cleaner inspection. I believe the holes you can punch change the internal pressure inside the filter enough to defeat the ADBV. I am only 3 hours into my first run with the Carquest 85515 with my IO-360 on an experimental cub and so far, so good. It has more efficient media and 30% more media area than the champion.