Union Sangyo oil filters

[Patcon]

I think it's always a good idea to preoil an engine before firing. All the way up to the cam

[Captain Obvious]

2 hours ago, ETI4K said:

So, I guess this is where things get interesting.  First, my focus is on the first few moments after startup - not when the motor is in some state of 'equilibrium'.  During that time, I am assuming an oil filter is not full of oil and there is not enough oil residing in all the passages, etc. to be able to impart any real resistance to flow.

The filter has an anti-drainback valve that keeps the filter full even when the engine is shut off. No differential pressure even when first starting.

And when you change the oil and put on an empty filter? There's no oil in the filter, so you can't bypass dirty oil. There's no oil to bypass,,, clean or dirty.

[ETI4K]

Comments appended:

The filter has an anti-drainback valve that keeps the filter full even when the engine is shut off.  -  True, and it's generally held that silicone ADBVs are considered "better", presumably bc the others do not reliably seal against drainback.  So I am asserting that all oil filters are not full at startup, and in my case specifically, mine isn't.  Further, as far as I am aware, there is no mechanism retaining oil in the filter on its discharge side.  Leaving an engine at rest for an extended period of time (however much that is?) would likely relieve the filter of at least some of its otherwise retained oil.

No differential pressure even when first starting.  -  There will always be deltaP even if the filter is completely full bc the oil galleries are not full and at normal operating pressure at startup, and all filter media (even when new) offer resistance to flow.  Not until the oil system is fully pressurized will the pressure on both sides of the media be close in value.  Is the differential enough to crack the bypass?  I suppose if the filter has done some work and is loaded to some extent, the oil viscosity is just so, the startup rpm is on a steep portion of the pump curve, etc., etc., that it certainly could.

And when you change the oil and put on an empty filter? There's no oil in the filter, so you can't bypass dirty oil. There's no oil to bypass,,, clean or dirty.  -  When the pump picks up the new oil and sends it to the filter to fill it and then distribute it through the motor, the initial differential will likely be at its lowest potential, and not at all likely to bypass.  But consider this.  No oil pan completely empties itself.  There is always residual oil, and in older motors, often some "light" debris in the pan, at the least.  Further, if there is "heavy" debris, like metal pieces, it will rarely be completely flushed from the pan by draining the oil.  Adding new oil one quart at a time during a change may or may not deliver that debris into suspension for pickup by the oil pump.  But, I believe the quick change places pump the oil in quickly.  If that is enough to dislodge debris and get it into suspension, and they start the motor to check for leaks then it's a different equation.  Could any form of debris enter the filter and cause a leak in the ADBV by virtue of becoming jammed at the valve (I've seen this type of problem many times in air and water valves)?

This is getting too speculative, of course, but I am considering all forms of failure as I have a currently unexplained "bypass" event that damaged my motor. 

Of course, there are those who believe paper filters will tear, stamped steel bypass valves fail, and some filters are produced missing the bypass valve altogether.  I guess these would result in a bypass event as well.😁

 

[Zed Head]

3 hours ago, ETI4K said:

I have a currently unexplained "bypass" event that damaged my motor. 

How have you determined the cause of the damage?

[ETI4K]

For all intents and purposes, the motor was new when I built it.  Block was align bored, decked, cylinders bored.  Head was shaved, valve job.  New pistons, rings, pins, oil pump, water pump and on and on.

Drove the car maybe 10-15K miles before putting it on the rotisserie (1997).  Upon disassembly of the motor this past Jan found hard debris and metal shavings in the oil pan and head.  The oil pump was badly damaged, journals scratched, cam towers worn past use.  Interestingly, the machine shop just told me that one piston/rod was 12 grams lighter than the others which were all within a few grams of each other.  When they removed the pins and weighed everything separately, that one piston weighs 19 grams less than the others.  I'm going off memory here, but I think that is near one half cubic inch of aluminum.  Machinist says the (ITM) piston looks fine.  Hoping to pick up everything from the shop next week so I can see for myself.

I get the oil pump would be damaged, but can't understand how the other parts ever saw debris to damage them.

 

 

[Racer X]

The bypass valve in the filter is to allow oil to be supplied to the engine in the event that the filter becomes clogged enough that it can no longer pass oil sent to it by the pump. With the multi viscosity oils of today, on cold startup the viscosity of the oil is low enough that the bypass shouldn’t be opening.

Clogging of the filter media to the point that the bypass opens happens one of two ways.

1. The car is neglected and maintenance ignored for so long that the lubricating oil becomes so fouled with dirt and carbon (carbon is what makes the oil black over time) that the filter becomes clogged and oil can no longer flow through it in enough volume to keep the engine lubricated.

2. A component fails (bearing, piston skirt, rings and ring lands from detonation, etc.), and the resulting debris gets forced into the filter and it becomes clogged enough to block the flow of oil.

In either case, bearing damage will result.

And we all know what happens next.

 

 

Edited June 11, 2021 by Racer X