Oil filter bypass valve

[schiker]

I wouldn’t see having 2 ways to bypass the filter media either in block or in can as harmful assuming the bias was comparable.

I would like the in can filter to bypass just a tad higher so the media doesn’t get cleaned bypassing and maybe it could function as a backup in case the in block bypass somehow stuck shut.

 

[WarWagon]

At some point we got to step back and ask how much stuff a (full flow) filter is going to filter? The oil pump screen is subject to sludge blocking on some engines as well as the oil pump "eats it first" then sends the debris and oil pump debris on to the filter. Assuming it doesn't lock the oil pump up and snap the driveshaft in the engine failure mode...

I suggest dirt the air filter missed, dust seals let in from negitave crankcase pressure, wear metals, debris from repairs (no matter how careful you are or aren't), and soot that has turned to sludge. Again looking in used filters at the settlements in the 'bottom' of the can some filters do actually filter stuff. (Others @Will L. are no better than a T-shirt stuffed in a can aka: defective junk.)

 

[schiker]

I think the science is starting to get a tad clearer.

I have mine blocked,with a tiny hole drilled in it. Without a bleed hole , sometimes after an oil change,it would loose prime,no psi untill I would loosen the filter and bleed it.

Nahhh I guess the bypass won't hydro lock as oil that bypassed could travel on through the standard path and its not sealed at the end. I momentarily thought the bypass might be backed into sorta a corner above the cup with hole in it and it might cold hydrolock sort of.

But what about this.......

The oil pump is a gear pump positive displacement right. As like most pumps Its great at pushing but not so great at pulling. I was reading about a different gear pump that could self-prime 20 ft of a water column (~ 8.6 psi). But it doesn't say how long it takes to establish flow or what the cause and effect of exit pressure. Biggie here how long it might take to establish flow which would depend of pipe sizing and any leakage! It said it helps to have the gears wet. Thinking when I have worked occasionally with sump pumps and sometimes they prime fast other times not; air leaks are killer.

I think the oil pump should act similarly. It can push upwards of ~90 psi but might not be able to suck more than ? ~12psi?. Then think of conservation of flow it might only have ~ 12-14 psi ? of pressure to push (as it might not have much slippage wet and flowing oil but air? I would assume it isn't as airtight like a vane pump at priming because it hasn't picked up the oil flow yet. It sorta sits there and cavitates because the oil ahead of pump hasn't moved.

Because you want to establish flow quickly and get oil to the bearings you need a very small weep/prime hole to allow maybe a path of small resistance so it can bleed off this air pressure priming force and so the pump can pick up oil and build enough oil flow and thus oil pressure to exercise the bypass valves if the oil viscosity it requires due to temperature and flow resistance.

Don't hold me to the exact numbers above the bypass differential for the oil cooler might be ~20 psi and the oil pump can't build that priming especially with the head pressure required to get oil moving through the whole path in front of the pump.

The weep hole would mainly be for oil changes or because the drain-back valves are not airtight or fail so the oil pump pickup tube and gears get a small enough air pocket sometimes that might cause excessive priming time.

 

[schiker]

It's not like it has a lot of head to pull up but its more it can't push oil ahead to get stuff moving cause the air can't escape from around the gears to prime. The oil is just thick enough to slow the bubble of air that has to move to prime and an air bubble can't flow downhill.

 

[schiker]

Maybe it has something to do with the volume of air that might get trapped in any kind of inverted P trap for air bubble above the gears vs the volume of air below the gears to the oil pan? So that the oil cooler can't create a giant inverted air P trap bigger than the pickup tube volume.

 

[Will L.]

Yeah, here is the cure for that:
the magic of a prelube system and can supplement momentary drop of oil pressure from hard cornering, huge bump, etc. The fact that we can have it turn on during glowplug cycle seems like they are made for each other.

 

[Will L.]

My thought on this is- most improved engine designs - the newer ones- are all leaning towards in the filter valve.

Anytime you have a disruption in flow, the worse the results are. You are better to have any restrictions or flow alterations in one area. And if there is cold start issues of the valve working for that reason- it is already being halted in the filter- so it makes sense to me the reason they are going in the filter.

Keeping more laminar flow once out of the filter just seems smarter.