Understanding the oil filter canister ..

[elwood]

Hey guys, can someone explain to me how the oil filter canister works ..
I mean, duh, it goes in the top under pressure, and out the bottom .
Problem is, I pulled the filter out of the canister on my 50 F1, and the canister was still half full of oil, I even took the canister off and held in my hand and the oil still didnt run out the bottom fitting, so I pored it out and cleaned the canister,
Is there a check ball in the tube or something Im missing ?
Thanks ..

[JSeery]

Not sure what you are referring to exactly. The oil goes in through the side and out through the two small holes near the top of the center tube. The oil system is under pressure, the pressure forces the oil through the filter material. So, it's not in the top and out the bottom as far as the filer cartridge is concerned. It is sealed top and bottom. The oil comes in the side and flows around the outside of the cartridge and is forced through it by the oil pressure. The oil inside the cartridge flows through the drain holes in the center tube and then down the center tube to the return tubing to the oil pan. Is that the question you are asking?

The oil will only drain down to the level of the return holes in the center tube. 51merc has a photo of the holes, but doesn't seem to like me posting it! Maybe he will respond with the photo.

[51 MERC-CT]

Originally Posted by JSeery

The oil will only drain down to the level of the return holes in the center tube. 51merc has a photo of the holes, but doesn't seem to like me posting it! Maybe he will respond with the photo.

Wrong assumption, post away!

[JSeery]

Cool. I think 51merc's photo are really helpful in understanding how the by-pass filter return works. The second illustration shows the oil path though the whole system.

[rotorwrench]

The .060" orifice at the entry port cuts the pressure down quite a bit. It's further cut down a bit by the filter media. After passing through the media, it's almost a gravity flow back to the oil sump. When the oil is warmed up, it flows pretty well but there is always some in the can when you open it up for servicing. This allows for some settling of solids that don't make it through the filter. I always clean the solids out at filter replacement but that is a nasty chore.

[flatjack9]

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If you look at JSeery's post, you will see that the restriction is located inside the canister, not on the inlet fitting.

[19Fordy]

elwood, it's normal for the oil not to fully drain out of the cannister.
Use your turkey baster and suck it out or absorb it with an old rag. No need to remove the cannister each time you change your oil.

[51 MERC-CT]

Originally Posted by flatjack9

If you look at JSeery's post, you will see that the restriction is located inside the canister, not on the inlet fitting.

The restriction hole is located in the fitting that screws into the side of the filter.
There are two drain holes in the center tube that together are twice the area as the main restriction hole in the fitting.`
The oil level in the filter will not go lower than
the two drain holes in the center tube.

[Mart]

Yes, it makes more sense to restrict the oil on entry. If it were restricted on exit the filter would be under more pressure and would be more likely to leak.

Mart.

[flatjack9]

I can't tell you how many of these I have taken apart that have no restrictor on the inlet fitting. The size of the hole on the inlet will have no effect on the pressure inside the filter. A smaller hole might take it a little longer to build pressure, but once full the pressure will be the same unless it can drain out faster than the oil coming in.

[elwood]

Thanks guys, always good feedback here ...
Cheers .

[JSeery]

The whole idea is for the oil to drain out faster than it comes in. Some bypass filters have the restrictor at the outlet fitting on the rear of the block.

[flatjack9]

Then there would be no need to seal the cover.

[Mart]

I can't respond to these comments without getting all "keyboard warrior"-ish. I don't want to do that.

But there is a reason why it is preferable to have the restrictor (.060" is factory spec) on the feed side of the filter. If you can't understand that, I can't explain it any different.

There is also a reason why you want to seal the cover. There is a built in resistance to flow in the filter itself, as the oil gets pushed through the filter element.

If you put an oil pressure gauge in the feed to the filter after the restrictor it will read a lower pressure than the pressure the engine is running at. The pressure will be the pressure generated by pushing the oil through the filter and flowing through the pipes and back to the pan. the restriction here is (hopefully) less than the .060" restrictor at the feed. So the pressure in the filter, and the pressure trying to get out of the lid is lower than the running pressure of the engine. The .060" restrictor also limits the amount of oil being bled off the main engine oiling system.

If you have no restrictor, the filter would be receiving a bigger volume of engine oil and the pressure would be higher due to the increased volume being pushed through the filter and the drain pipework. The engine oil pressure would be lower due to the extra amount of oil being bled off through the filter.

If you put the restrictor on the return line between the filter and the pan, The oil bleedoff from the engine would be the same as before, but the pressure in the filter would equal the engine oil pressure. Hence the sealing of the lid would be more critical.

That is why you want the .060" restrictor in the feed and why you want to put the lid on properly.

Mart.

[Frank Miller]

The restricter keeps pressure form being bled off the oil system. This is a partial flow system. Once warm the oil will drain as fast as it goes in. I know this because I had a leak at the cover gasket that only leaked when it was cold.

[Phil Gillespie]

Oil Bypass Filter:
Just read through the info on this filter. Have been having some leakage perhaps to over pressure. Checked my inlet and it is not restricted to 0.06". The inlet size is 3/16" instead of 1/16".
So figure I need to close to inlet to recommended 1/16" as return holes in centre tube are similar size. Hence inlet and outlet will be same size as per above pics.
This is correct?
Thanks,
Phil NZ

[51 MERC-CT]

Originally Posted by Phil Gillespie

Oil Bypass Filter:
Just read through the info on this filter. Have been having some leakage perhaps to over pressure. Checked my inlet and it is not restricted to 0.06". The inlet size is 3/16" instead of 1/16".
So figure I need to close to inlet to recommended 1/16" as return holes in centre tube are similar size. Hence inlet and outlet will be same size as per above pics.
This is correct?
Thanks,
Phil NZ

By not having the single .060 dia. restrictor hole in the inlet to the filter an over pressure build up plus a rise in the normal oil level will occur inside the filter, possibly causing leaks.

[Phil Gillespie]

Originally Posted by 51 MERC-CT

By not having the single .060 dia. restrictor hole in the inlet to the filter an over pressure build up plus a rise in the normal oil level will occur inside the filter, possibly causing leaks.

Yes thats how I see it and this is well explained by Mart. So wil have the inlet
filled and redrilled to 1/16".
Phil NZ

[Phil Gillespie]

Originally Posted by 51 MERC-CT

By not having the single .060 dia. restrictor hole in the inlet to the filter an over pressure build up plus a rise in the normal oil level will occur inside the filter, possibly causing leaks.

Another valid point concerning the rise in normal oil level inside the filter which is what i had experienced with the 3/16" inlet hole to filter.
It makes good sense inlet flow to match outlet flow.
thanks,
Phil NZ

[Steve in Denver]

I understand the flow pattern. Besides the turkey baster, would it make since to put some kind of drain plug offset in the bottom of the canister?
Steve in Denver, CO