Full oiling and trapped oil

[mcjweller]

Hello!

So, not a novice engine builder, but a novice VW builder, and I have a question about full oiling. When you block off the factory oil path from the pump up to the main oil galley, and redirect it (from a filter) into the end of that gallery instead, doesn't the pump discharge bore fill with oil above the block-off (coming in from the filter) that can never drain, recirculate and/or just age and accumulate trash as it breaks down? Or worse, does it form an air pocket that can shift or introduce air bubbles as the motor moves around with driving?

I'm running full oiling, but cannot figure out how either of those two scenarios would not happen. But many people run it without issues so, I have to ask the question. What am I missing?

[Glenn]

You're thinking too hard.

I've been using full flow oiling for hundreds of thousands of miles and never had a problem due to that.
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Glenn
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[oprn]

What you are missing is that it doesn't matter. If dirt gets down there and gets trapped... so what? It's not going anywhere. As for air... can't see it happening or being an issue if it does. There are lots of other dead ends in the case where the holes are plugged after the galleries are drilled. Same deal.
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Our cars get old, we get old but driving an old VW never gets old!

[modok]

It probably fills with oil.
No air bubbles, because gravity.
Why does it matter?

90% of air bubble problems are on the suction side, so, focus you attention there.

[mcjweller]

I once rebuilt a motor that had 1/2" tall boss on the drain plug in the bottom of the pan. Meaning that at every oil change, no oil would drain below that boss. The oil that remained in that motor oil change after oil change contaminated the fresh oil immediately. In a bug, it kinda defeats the purpose of a filter, if immediately after the filter you've got a repository of contaminated oil that you can never drain or clean out.

That is, if that's what happens...

Its under pressure, I'm curious to know if the fluid dynamics will scavenge/flush that section over time or if it just sits there. And I was curious if anyone had looked into it.

[modok]

It will collect sediment, as most low hanging dead end areas do, but as long as the car stays upright it won't dislodge over time.
This area holds what.....10cc of oil? Or so, that's a drop in the bucket compared to the big picture.

[mikedjames]

My main annoyance is the oil that sits in 10ft of hoses and the cooler outside the engine that does not get changed. But that pint or half-litre does get diluted by the oil change.
I do disconnect one end of the cooler and drain it on an oil change.
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1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[modok]

If there is any link between...what you call it...."residual oil not changed" and engine life, I have not seen it.

In fact, just looking at the statistics... of cam failures in complete rebuilds VS camshaft only replacement, I've wondered if adding a quart of used oil to a fresh engine might actually...... be a good idea?

And I thought of that many years ago and have been since on the lookout for any clue to support or bust that preposterous idea....and I got nothing so far.

But think about it....the oil at the flaps store... is formulated for oil changes, where only 80% of the oil gets changed, and they know that, so, just use as directed......
and for new engines, use break in oil
it's not being crazy, it's just following the logic

[oprn]

Drive the car around the block and you have used oil. Drive a car off the new car lot and you now have a used car.

I am in the habit of changing the filter every second oil change (still nothing in it when I open it up) so I start with 1/2 quart of used oil plus whatever is in the valve covers and sump that doesn't run out.
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Our cars get old, we get old but driving an old VW never gets old!