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Old 11-25-2018, 12:31 PM   #1
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Question for diesel engine experts

I have a Puradyn by pass filter that when saturated probably holds about 3/4 of a gallon of oil. The oil supplied to this filter is from the pressure side of the system, pushed up through the inside of the filter, passing through to the outside and then gravity fed back to the sump.

This creates a situation where the oil level can be full when the engine is off, but low when the engine is running at idle and the filter is saturated. It isn't below the add oil mark when running, but my question is whether I can safely overfill the level when the engine is off so it is full when running without putting stress on the seals, since there is a path for the excess pressure on startup to presumably go via being pumped through the bypass filter?

Hopefully the question is clear....
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Old 11-25-2018, 12:58 PM   #2
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Question since I don't know the Puradyn in particular.
Where is the output line back to the engine attached to the Puradyn?

If the output line is at the Puradyn top or near it the oil, once in the filter, will remain in the filter at shutdown time. The bulk of the oil won't drain back to the engine sump except the minimal amount in the final line or any that is above the return oil line attachment point.

The only time you would need to add more oil to take care of the Puradyn volume is at the initial filling or oil change interval.

I do not have a Puradyn but do have a bypass filter, Cummins, which holds approx 5 litres of oil. I fill it directly as best I can , then run the oil pump untill the alarm quits, start the engine to run for a couple minutes to pressurize the entire system, shut down, allow time for drain back, and then recheck the sump level and adjust as needed.

Next oil change time I drain out about 4L of oil from the bypass filter into a pan. Some oil is trapped in the element itself and will not drain to the pan. It is a whole lot heavier at change time than when I installed it.

So based on my own experience the oil does not drain back to the pan assuming the return line is at or near the top of, in your case, the Puradyn.

The oil is trapped in the Puradyn if my question above is correct.

No, I would not add extra oil to "take into account" the Puradyn volume as I think you will overfill it.
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Old 11-25-2018, 01:05 PM   #3
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Can you ask the engine manufacturer whether 3 quarts overfill is a problem? Even in n a heavy seaway?

Some engines can take low oil pretty well, but some can't take excess oil hardly at all....

Try to find out what you have.
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Old 11-25-2018, 01:39 PM   #4
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What engine?
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Old 11-25-2018, 03:14 PM   #5
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I have old Detroits that have bypass filters, not full flow filters. They hold about 3 quarts. As C lectric says, when changing oil, either start with extra oil or run the engine and add oil after shutdown. Depends on the engine make if you can have extra oil in the pan. I could probably put two extra gallons in the Detroits.

I don't change my filters very often because now I centrifuge the oil below what the filters can catch. I only change the oil if it fails a test. So far that's never. Makeup oil seems to keep enough additives.
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Old 11-25-2018, 04:08 PM   #6
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Quote:
Originally Posted by C lectric View Post
Question since I don't know the Puradyn in particular.
Where is the output line back to the engine attached to the Puradyn?

If the output line is at the Puradyn top or near it the oil, once in the filter, will remain in the filter at shutdown time. The bulk of the oil won't drain back to the engine sump except the minimal amount in the final line or any that is above the return oil line attachment point.

The only time you would need to add more oil to take care of the Puradyn volume is at the initial filling or oil change interval.

I do not have a Puradyn but do have a bypass filter, Cummins, which holds approx 5 litres of oil. I fill it directly as best I can , then run the oil pump untill the alarm quits, start the engine to run for a couple minutes to pressurize the entire system, shut down, allow time for drain back, and then recheck the sump level and adjust as needed.

Next oil change time I drain out about 4L of oil from the bypass filter into a pan. Some oil is trapped in the element itself and will not drain to the pan. It is a whole lot heavier at change time than when I installed it.

So based on my own experience the oil does not drain back to the pan assuming the return line is at or near the top of, in your case, the Puradyn.

The oil is trapped in the Puradyn if my question above is correct.

No, I would not add extra oil to "take into account" the Puradyn volume as I think you will overfill it.
When the engine is off, the oil just gravity drains back into the sump because the return line is at the bottom of the cannister. Some oil certainly stays in the filter, but quite a bit drains back to the sump. It is that amount that means that if the system is "full" when running, it is overfilled when off.
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Old 11-25-2018, 04:08 PM   #7
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What engine?
It's a CAT 3306. The dipstick says "Do Not Overfill".
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Old 11-25-2018, 04:10 PM   #8
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Originally Posted by Lepke View Post
I have old Detroits that have bypass filters, not full flow filters. They hold about 3 quarts. As C lectric says, when changing oil, either start with extra oil or run the engine and add oil after shutdown. Depends on the engine make if you can have extra oil in the pan. I could probably put two extra gallons in the Detroits.

I don't change my filters very often because now I centrifuge the oil below what the filters can catch. I only change the oil if it fails a test. So far that's never. Makeup oil seems to keep enough additives.
I believe I could do the same thing, but for the cost of an annual oil change, I just go ahead and do it.
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Old 11-25-2018, 04:14 PM   #9
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The cure could be just to install a shut off valve on the return line from the Puradyn to the sump, and close it when the engine is turned off. That isn't hard to do, but adds some complexity I'd as soon avoid if it turns out that an overfilled sump isn't a problem as long as their is someplace for the excess oil to go after startup, which in this case would be in filling the filter. That is what I'm not too sure about, but I would assume that having an outlet for excess oil is a very different set of conditions than starting the engine up with no place for the oil to go other than circulate.
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Old 11-25-2018, 06:21 PM   #10
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What matters is not the oil level when sitting, but the oil level when running. Presumably the bypass filter is full when running, but empties when sitting. Then fills right up on startup. So it is ok for it to be a little over the full mark with filter drained. You could check it right after shutdown while filter is full, if above the add mark it is ok.
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Old 11-25-2018, 06:56 PM   #11
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What matters is not the oil level when sitting, but the oil level when running. Presumably the bypass filter is full when running, but empties when sitting. Then fills right up on startup. So it is ok for it to be a little over the full mark with filter drained. You could check it right after shutdown while filter is full, if above the add mark it is ok.
Thanks Ski, that is what I hoped, and it makes sense. Besides, I will usually run the engine for 10 minutes or so at idle before powering up (pulling anchor, motoring out of a marina), so the oil pressure isn't at the high end before the excess oil is pumped into the Puradyn cannister/filter.
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Old 11-25-2018, 07:34 PM   #12
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Loop it

Would this work?... Put a longer hose on the drain side of the filter and loop it higher than the top of the filter and then it would not drain back into the sump. When it is time for an oil change you could release the loop and let the oil from the canister drain down to the sump making the oil filter change much easier. ???
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Old 11-25-2018, 07:48 PM   #13
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Would this work?... Put a longer hose on the drain side of the filter and loop it higher than the top of the filter and then it would not drain back into the sump. When it is time for an oil change you could release the loop and let the oil from the canister drain down to the sump making the oil filter change much easier. ???
That's actually brilliant, and it seems like it would work fine. The oil pressure would push the oil up the loop and into the sump when the engine was running, but not when it wasn't. Very clever, mon Capitaine....
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Old 11-25-2018, 07:58 PM   #14
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Merci Beaucoup, let me know if it works for you.
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Old 11-25-2018, 07:58 PM   #15
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I have Puradyn external oil filtration on my Cat 3406’s. Original owner put them on after 500 hours. Boat now has 5500 hours and the motors hardly smoke at all and burn very very little oil. Seems to have been a good investment.
Regarding the draining of the oil back into the crankcase, I didn’t think about that and appreciate you bringing this up.
I’ll be sure to check the level right as I shut down the motors after a trip.
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Old 11-26-2018, 06:55 PM   #16
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Cummins 6bta 5.9 m3 335hp

Anyone have a good fuel burn rate at cruise speed (say 8-9 knots) Cummins 6bta 5.9L M3 335 hp. Iím looking at economy. Not sure if this is the engine. Any help is appreciated
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Old 11-26-2018, 07:58 PM   #17
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Coalman,

Far too open ended a question. A huge amount depends upon the boat, how the hull loads the engines and how YOU run it, not the specific engine.

The hull may be quite good at 7 - 8 knots but if you insist on running faster by even , to you , a small amount more speed the engine may use a disproportionate amount more fuel.

The engine you asked about can be very good on fuel, it's all how you run it.

Need more info such as the boat, hull type, boat length to even start.

Also not trying to be snarky but this should have been in a separate thread so the original thread is not hijacked..
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Old 11-26-2018, 08:35 PM   #18
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Not sure the hose idea would work as (without a siphon break) it is likely to siphon back. You might be able to arrange the hose to enter the engine above the filter, and create the siphon break.

However, I would not be worried about it. On a cold engine, if you look at the oil level at startup, first it goes way down as the cold oil is pumped up into the rocker box and elsewhere, and is slow returning as it is cold. Then the level comes up as the oil warms and drains better. It takes only a few seconds to pump quite a bit of oil out of the pan, it's hard to imagine some extra oil in there causing a problem in that few seconds, even if the crank is churning it. Overfilling while in normal operation will cause foaming due to crank windage, not a good thing, but not a problem in a very temporary startup situation.
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Old 11-30-2018, 05:32 PM   #19
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Engine oil level

There might be a lot of overthinking going on. I'm certainly not an expert on much of anything, but here are my opinions: First, don't check the oil with the engine running. The fill level was set by the manufacturer assuming the engine is shut off, not running. Also, I wouldn't worry about the filter draining in any reasonable time. To drain, there has to be a way for air to get into the filter housing, and there isn't an easy way for this to happen. Where would it come from? Sure, after a long time sitting (months), the filter might drain down. I would fill to the mark after an oil change, start the engine and then measure again after shutting it off. Fill it back up to the mark and forget about it. Whether the oil level is somewhat higher or lower than the mark there will be no effect on oil pressure. When too full the oil might be aerated if it gets up to the crankshaft, but that won't have much effect. And it has to get really low before the pump will start picking up air.
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Old 11-30-2018, 05:54 PM   #20
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I have Puradyn external oil filtration on my Cat 3406ís. Original owner put them on after 500 hours. Boat now has 5500 hours and the motors hardly smoke at all and burn very very little oil. Seems to have been a good investment.
Regarding the draining of the oil back into the crankcase, I didnít think about that and appreciate you bringing this up.
Iíll be sure to check the level right as I shut down the motors after a trip.
I decided the simplest thing to do was add a ball valve at the bottom of the unit that can be turned off when the engine is shut down. This will trap the excess oil in the cannister. I like the design C Lectric described, where the return to the sump is at the top of the cannister. Except, I suppose, when it comes time to change the filter, but I doubt that is much of a bother dealing with the excess oil.
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