Another Low Oil Pressure Query

[Shaneesprit]

Originally Posted by wingssail

Thanks for the comments.

We're back in port again after a great sail today (20 miles upwind then a finish downwind in 20 knots, a bit dicey on getting the genoa off but we did it).

As to the comments about oil change intervals ands sludge build up.

I have to say we've seen no indication of any sludge build up. The pan was off two months ago and everything was clean, pan, crank, oil pick up, anything we could see. The valve cover was off a year ago, also clean. And even now, when I eyeball inside with the the oil filler cap on the valve cover off, there is nothing black. So I think the engine is clean. of course that says nothing about what is inside the oil passages, maybe we will find out.

As for our oil change intervals; unfortunately my logbook does not include these (it will in the future, my bad). But while we don't have a regular interval, we change periodically, usually before any passage.

Now that we can work on the engine without worry about not being able to run it (we have shore power) we'll proceed as several people have suggested.

Thanks for the ideas, we'll keep you all posted.

As to the lack of sludge, possibly another sign of you using the Engine for charging batteries, what happens is the cylinders run cold the the rings don’t expand and close up, so your sump probably has diesel in it, it’s a normal consequence of light load running,
Diesel is a great engine flushing oil, although you don’t want it in the sump when your running.

Change the oil the filter and the pressure regulator, make sure you use a B3 or B4 oil from a major producer - not the supermarket.
Oil pump rebuild / replace.

On bearings - Big ends knock when reved and main bearings rumble.

You have a choice
1) service often and run until it fails
2) do the above oil + filter + regulator + oil pump? and if that doesn’t bring it back Engine out.

Personally I would be planning a winter rebuild, if you can’t get the pressure back

[wingssail]

Originally Posted by Shaneesprit

As to the lack of sludge, possibly another sign of you using the Engine for charging batteries, what happens is the cylinders run cold the the rings don’t expand and close up, so your sump probably has diesel in it, it’s a normal consequence of light load running,
Diesel is a great engine flushing oil, although you don’t want it in the sump when your running.

Change the oil the filter and the pressure regulator, make sure you use a B3 or B4 oil from a major producer - not the supermarket.
Oil pump rebuild / replace.

On bearings - Big ends knock when reved and main bearings rumble.

You have a choice
1) service often and run until it fails
2) do the above oil + filter + regulator + oil pump? and if that doesn’t bring it back Engine out.

Personally I would be planning a winter rebuild, if you can’t get the pressure back

Thanks for the comment Shaneesprit, I'm not really trying to keep this thread going, people have other things to do than follow my oil trials and tribulations, but I thought I'd respond to your comments specifically.

After installing a good mechanical oil pressure gauge we do now know that the oil pressure is a consistent 55lbs/in2 so that is a big relief to us. We don't currently have a concern about the oil pressure regulating valve.

We have never let the engine run cold while charging. Coolant temps (79c) and head temperatures (71c) are normal when we operate the engine including when charging batteries at anchor or while sailing. We have not noticed any dilution of the lube oil with diesel except when we had an injector problem one time and when we had a fuel pump problem one time. Both issues were identified and corrected quickly.

Other than this current issue we have not detected any wear or consequence from our 6000+ hours of running the engine to charge the batteries. There is no smoking, little or no blow by, no excessive or unusual noise, no difficulty starting and no obvious loss of power. So I am not convinced that running the engine primarily to charge the batteries, has been harmful. I could be wrong.

But we still have a concern about reduced oil flow in the rocker/tappet/ valve area. There is lubrication but not the flow I have seen previously.

So here we are. We have flushed the engine with a commercial product, changed the oil and filter, and have everything reinstalled back to normal. We will continue to operate the engine and monitor it closely and replace the oil pressure sending units as soon as I can get them (on order). I have no intention of running it until it fails. If the lubrication or pressure deteriorates further we will remove and examine the oil pump, probably replace it. Nor do I intend to plan an engine rebuild this winter. For one thing we sail continuously during the winter (and spring, and a lot during the summer and fall) and I am not interested in taking the boat out of service for an expended period of time and spending a heap of money unless I see some reason to warrant it. Right now I do not. When it becomes necessary we'll do it at that time, regardless of the season.

As for B3 or B4 oils, ACEA oils are not generally available in North America or in many places in the world where we have travelled. We have always used the best oil we could find. Currently we are using API SN/SM oil.

[a64pilot]

My theory of why there is a pressure regulator in the pump and another mounted by the oil filter is simple, they had a shed load of oil pumps with pressure relief valves and manufacturers tend to use what’s in stock as opposed to sourcing a new part and obsoleting a whole lot of functional parts, plus parts commonality is a good thing, for instance back in the day ALL GM motors used the same lifters, from the little four cylinder to the big 500 cu in Cadillac motor. So that pump may find itself in many motors, some maybe not having a second relief valve.

But back to the Yanmar, I’d bet the pump is shimmed so that it never, ever opens, the valve is pretty much bypassed, so the one by the oil filter can be adjusted, cleaned or replaced without engine removal.

Just as an example, I believe some Yanmar’s have oil drain plugs, want to be that oil pan is also used in some kind of tractor or forklift or something?

If your a manufacturer and have manufactured many other things in the past, when it comes time to manufacture a new product, a smart manufacturer first goes on a parts hunt to the warehouse, it’s actually called potato head manufacturing.

[Compass790]

As for B3 or B4 oils, ACEA oils are not generally available in North America or in many places in the world where we have travelled. We have always used the best oil we could find. Currently we are using API SN/SM oil.[/QUOTE]

You should use an API oil with a C in the rating S stands for spark ignition & C for compression ignition. If the oil is suitable for both petrol & diesel it would say something like SN/CH-4.
I dont know how much different they are but thats the classification.

[Scubaseas]

A64pilot. Apologies to wingsail/OP for the hijack. I do not have the 3Jh2 manual but my 4Jh5E manual has the same set up and an oil pump pressure spec of 52 to 49PSI (i recall it was the same pressure as the pressure regulator on the filter housing) this being for the pump itself's relief valve which is not field adjustable. I've seen a few dual spring set ups and it's typically to reduce the line pressure to the cooler and the turbo if it has one. I get the concept of make millions of one part versus hundreds of different parts to do the same thing. But other than they already have lots of the one filter housing I don't see the benefit of regulating the pressure at two locations and have it at the same pressure. Unless they are using it as a check valve to stop drain back from the oil cooler and squirters? No idea. Is what it is. Easy to see why it has to work.



Wingsail. You need a "C" rated oil. Like Compass790 says. The C means diesel and typically is higher detergent than S oils. Most oils these days are CK or CL which are fine. CC and CD went away a long time ago.



My only concern is your observation of possible lack of flow to the rockers. If it's better after the flush I wouldn't worry about anything but to keep an eye on the pressure once in a while. Glad it worked out for you. Kudos for your excellent observations and being able to clearly articulate the situation. A lot better than the usual "sometimes it's withdrawn and sullen and sometimes it's openly hostile" descriptions I used to get from customers. Your plan sounds solid.

[jimbunyard]

Enough.

Apologies Wings, was going to let it go, but this endless speculation from people who should know better is silly.

All the information needed to know about the specifics and operation of the lubrication system for your engine has been linked to or specifically shown.

There's no need to assume different engines, whether they're from the same or different manufacturers, operate the same as the one in question, or invoke specs from one engine as proof that this engine's specs must be the same.

That is unless one assumes there's some kind of 'manufacturer's conspiracy' to hide the truth of either their design or marketing or manufacturing or engineering philosophies.

I can assure you all, there are no 'unnecessary parts' on the engine in question. Nor are there any used that are 'left-over stock'; parts just looking for an engine to be thrown onto.

That's not to say that if a part from stock can be used (if it fits the necessary parameters) it won't be used, but to suggest, for instance, that an off-the-shelf oil pump is modified so that part of it is inoperative, and included in the design of an engine because it is available from stock reflects a basic misunderstanding of modern economic and design practices and realities.

But back to the point: the operation of the lubrication system.

From the manual for the 3JH2E, TE

https://www.manualslib.com/manual/73...age=122#manual

The first picture below is an oil flow schematic. As can be seen, the path is well described and does not follow the route that some have suggested it must. It should also be noted that, while the Japanese/English translations have much improved since the 70's, there are still certain conventions used that make comprehension of some aspects a little difficult and ambiguous. In this context, I'm referring to the conflation of 'screen' and 'filter', and the interchangable use of 'regulator', 'relief' and 'control', where it really isn't interchangable, at least not if the manual's producer is interested in the most efficient transfer of information...

Anyway, this is how the system works.

The oil is picked up through the first 'filter' (what most English-speaking mechanics would call the 'screen), and is pumped through the 'regulator' valve (which most mechanics would call a relief valve, since that what it does; relieves overpressure). It is interesting that this valve opens at 3 kg/cm2, or 42.67 psi, which is substantially less than what (most would call) the regulator valve downstream operates at. How can this be? Well, I'm not doing all the work for you; suffice it to say that pressure is a function of 3 properties, and, if I remember correctly, someone has already linked in this thread to this aspect of the puzzle.

To continue. The oil then goes at full flow to the second filter (what we'd call 'the filter' [which contains yet another 'regulator' valve]), and from there, also at full flow, to the oil cooler, and the turbo, if one is fitted.

Since this has turned into an essay, it's worthwhile to make a short detour regarding the cooler and how specific design and engineering can be. Second picture shows a cutaway of the cooler. I'm guessing here, but it sure seems to me that the thing is designed to both minimize thermal shock to the cooler itself and prevent (as much as possible) dry starts (meaning lack of oil at startup). I'll leave it to those interested to work out why I think that...

The cooled oil is then returned to the oil filter housing, where it goes through what Yanmar calls the 'pressure control valve' (but what is known 'over here' as the pressure regulating valve), where pressure is regulated between the range of 3.5 kg/cm2 (49.78 psi) to 4.5 kg/cm2 (64 psi). Remembering the necessary components of 'pressure', and the speed(rpm)-dependant variable-output volume of the oil pump should make it clear how and why this regulation is possible and necessary.

It may be interesting to some that whilst I was 'researching' this 'regulation problem', I came across a parts manual for a 3JH5E engine, used in a Kohler generator. Guess what? In a constant speed application, it appears that the 'regulating' valve integral to the oil pump is sufficient, since there wasn't one built into the oil filter housing (or anywhere elso my admittedly somewhat cursory look revealed).

From the pressure control (regulating) valve, the full volume (less any excess 'regulated' back to the pan) is fed into the main oil gallery, where it is distributed to the various parts of the engine, and thence back to the pan, where it starts the cycle all over again.

So there.

[Scubaseas]

The article was at https://www.melling.com/aftermarket-...u-k/technical/

Please explain to my ignorant self how you get an upstream pump with the relief valve set to 42.67PSI to generate pressure in excess of 64PSI downstream that needs a second piston/spring relief or regulation valve. Or does it work on the Escher Waterfall principle?

I'll apologize again if I pissed you off. Sorry but I disagree on using 75% diesel as an engine flush. Lack of lubrication qualities aside I would have concerns about the possibility of a runaway engine.

[skipperpete]

Originally Posted by Scubaseas

The article was at https://www.melling.com/aftermarket-...u-k/technical/

Please explain to my ignorant self how you get an upstream pump with the relief valve set to 42.67PSI to generate pressure in excess of 64PSI downstream that needs a second piston/spring relief or regulation valve. Or does it work on the Escher Waterfall principle?

I'll apologize again if I pissed you off. Sorry but I disagree on using 75% diesel as an engine flush. Lack of lubrication qualities aside I would have concerns about the possibility of a runaway engine.

While still on the subject of low lube oil pressure,that “Melling” article was very interesting. I’m also a critic of lube oil flushes and particularly diesel flushes unless it’s a static wash through. There is strong support for flushing by the folks who manufacture and supply the dedicated flush products so no surprise there, but I don’t quite follow the logic behind using diesel fuel and a bit of engine oil at very low viscosity.
If the flush is a success and any amount of sludge is displaced it can only fall into the oil pan and be picked up at the suction screen... to then proceed unfiltered to the oil pump.... then through a close tolerance pressure regulating valve to the full flow oil filter. Here some of it gets stopped (depending on the element particle cutoff size) until the element gets totally blocked and the full flow bypass in the filter pops and then totally unfiltered lube oil goes through to the main bearings and more significantly the turbo which runs on a cushion of oil from concentric tiny oil jets.
The viscosity of the flush oil /fuel mix is unknown but might be as low as 5W.
I’ve spent a lot of time keeping fuel oil out of Lube oil on Detroit diesels, Ford Lehman’s (and other variants) and most recently the 16 valve Yanmar 4JH which also have the injectors under the tappet cover.
Does any engine manufacturer suggest or recommend lube oil flushing?
Any opinions or advice would be most welcome.
Pete.

[Compass790]

OP does not have an oil pressure problem, I'm actually surprised how high his oil pressure at idle is given the hours on his engine.
Not to get too sidetracked by the Melling article but its my belief that it didn't pay enough attention to oil pump tolerances, just said replace at overhaul. That's a side issue tho.
However he may have a resistance to flow problem,somewhere on the path to his rocker covers.
Very much doubt he would get to 55 psi if his oil pump is faulty. Don't think he should concentrate his diagnostic efforts there.
Likewise his suction tube is hardly likely to be faulty if he can get to the 55 psi. It brings to mind the loose rocker arm tower on another thread but no evidence for that in this case.
I think the worn out oil pumps I see are due to picking up the unfiltered oil causing the pump to wear with sometimes quite big pieces of metal. Its a pity the oil filter is not before the oil pump. Haven't thought that thru but guess the engine manufacturer concludes that some oil is better than no oil hence the crude screen or holes.
I'd say bypass valve but anyway I'm digressing.
Pity OP has lost interest. I haven't

[Shaneesprit]

Diesel flush is fine no problem at all
However DO NOT START iIT with Diesel in the sump right up to the top of the dipstick or almost - way above normal oil height.
Crack the injectors and crank on starter ONLY
Diesel is one of the most aggressive cleaning agents out there but it is also oil based and a lubricant.
Use a cheap oil and filter but change it to some better branded oil after a short period.
It’s a bit old school but works, learnt that as an apprentice.

How did you run under load at 1800RPM ? I am assuming you put a line stern to the Dock and put in gear and tried to motor away?

[jimbunyard]

Been quite busy, so've not responded. Big job is mostly done, so we'll 'reopen' this 'old' thread...

Originally Posted by Scubaseas

The article was at https://www.melling.com/aftermarket-...u-k/technical/

Please explain to my ignorant self how you get an upstream pump with the relief valve set to 42.67PSI to generate pressure in excess of 64PSI downstream that needs a second piston/spring relief or regulation valve. Or does it work on the Escher Waterfall principle?

I'll apologize again if I pissed you off. Sorry but I disagree on using 75% diesel as an engine flush. Lack of lubrication qualities aside I would have concerns about the possibility of a runaway engine.

Didn't read the Melling article, I assume that beyond the point of selling Melling, it gave standard information about pumping principles and, pump operation, etc.

Could be several explanations for the (supposed) conundrum "...how you get an upstream pump with the relief valve set to 42.67PSI to generate pressure in excess of 64PSI downstream....".

Maybe the manual is wrong. Seen it plenty of times.

Maybe the valves are rated on different scales, perhaps working vs static pressure.

Or maybe it has something to do with volume and the actual operation of the first valve. Ever noticed how large the pickup tube inside diameter is in relation to the multiple 'outlets' (bearing clearances and cooling jets)?

Since I've no official "bona fides" (are you one of the Coens in disguise?) other than designing, building and repairing all things mechanical for as long as I can remember (and according to people who should know [parents and siblings] since before I can remember [about 9 or 10]), perhaps you can decide which of the three seems more likely, or can provide the real answer.

My guess is that the first pressure relief valve, far from being 'shimmed down tight", opens fully at 42 lbs, dumping volume, to avoid blowing the filter off or splitting the oil cooler housing. At X position, fully open, the pump, being positive displacement, having increasing rpms, and comparatively large output volume in relation to the bearing clearances, continues to build pressure until it is relieved by the second valve.

Of course, if this is correct , then semantically, the first valve should really be called a volume relief valve, but since the pressure and volume are so intimately related, perhaps the colloquial defintion is OK...

Not sure what the indications that I'm "pissed off" are; it would seem that a more accurate reading would be frustration at people who are obviously of much the same mental capacity and ability yet apparently fail or don't want to use them. It's almost seems a bit trollish...

Originally Posted by skipperpete

While still on the subject of low lube oil pressure,that “Melling” article was very interesting. I’m also a critic of lube oil flushes and particularly diesel flushes unless it’s a static wash through. There is strong support for flushing by the folks who manufacture and supply the dedicated flush products so no surprise there, but I don’t quite follow the logic behind using diesel fuel and a bit of engine oil at very low viscosity.
If the flush is a success and any amount of sludge is displaced it can only fall into the oil pan and be picked up at the suction screen... to then proceed unfiltered to the oil pump.... then through a close tolerance pressure regulating valve to the full flow oil filter. Here some of it gets stopped (depending on the element particle cutoff size) until the element gets totally blocked and the full flow bypass in the filter pops and then totally unfiltered lube oil goes through to the main bearings and more significantly the turbo which runs on a cushion of oil from concentric tiny oil jets.
The viscosity of the flush oil /fuel mix is unknown but might be as low as 5W.
I’ve spent a lot of time keeping fuel oil out of Lube oil on Detroit diesels, Ford Lehman’s (and other variants) and most recently the 16 valve Yanmar 4JH which also have the injectors under the tappet cover.
Does any engine manufacturer suggest or recommend lube oil flushing?
Any opinions or advice would be most welcome.
Pete.

As it seems (to me at least) that I constantly reiterate, I don't recommend or opine on anything that I've not done. Manufacturer's guidelines and recommendations should be taken as a starting point, a minimum, 'most often the case' scenario for new equipment, especially when fulfilling warranty requirements.

This doesn't mean they are the best practice in all applications or situations. As with most dynamic systems, knowledge and understanding of the specific system, and the remediating effects of certain operating principles and procedures on that system is at least as important as the manufacturers recommendations.


I started using engine flushes in the 80s, before I had much hands on experience with diesels, but plenty with gas engines, and certain seemingly deposit-prone engine oils (can anyone say QuakerState?).

Not exactly sure when I switched from 'commercial' engine flushes to diesel; with the advent of better oils, that 'engine flush solution' is required even less than it was before; for me it was never that common anyway.

But when it was required, it could work wonders dissolving gum, which causes problems like sticky regulating valves.

As for this dissolved gum being 'particulate' in nature, well, only in the sense of the 'particles' being molecular; anything actually particulate in the engine large enough to be dislodged and circulated by the oil system indicates a larger, different problem.

For a more recent (inadvertant) engine flush story, heres's one that addresses several of the questions posed, though there's no way to know the long-term effects without the passage of time...but it's been 2 years since this happened.

The pictures below show the valves and injectors of a GMC/Durama/Isuzu turbo diesel with 115,000 miles after being run, under load at highway speed, for at least two hours with 100 percent diesel. Needless to say this was not done intentionally, nor is this a recommendation that anyone do the same.

The cleanliness of the engine does illustrate the power of an engine flush in removing gum from the interior of an engine. Notice there is not a 'slight reduction' in deposits; there are no deposits at all. In the first picture, on the second rocker arm from the left, just adjacent to the cable tie(!) also notice as a 'cleanliness reference' the two 'crumbs' of dirt that fell from the valve cover when it was removed.

This 'flush' was caused by cracked injector bodies, and affected the operation of the engine not at all, except that the fuel 'consumption' went through the roof, and the 'oil' (diesel) pressure dropped from 40/65 idle/running to 20/35-40 idle/running.

What alerted the driver to the problem was the fuel gauge dropping from near full to almost empty on a 40 mile trip.

After changing the injectors , injector lines (2500.00 for parts, the 'advantages' of common rail) and oil and filters (3 times [the oil and filters. not the injectors and lines]) the oil pressure returned to normal, and continues so to this day (knock wood). I'd consider us lucky in this case and would certainly not recommend for anyone in any case to duplicate this uncontrolled experiment, certainly anyone with a relatively old school engine with high hours.

But that doesn't preclude using a combined diesel/oil mixture as an engine flush in a controlled manner, as previously suggested, when indicated.

If one doesn't want to, then don't. But it is a proven solution that has a long history of success.

[Scubaseas]

#86, Jimbunyard. You may want to look up "Pascal's Law" or "Pascal's Principle"

[a64pilot]

The reason the Duramax didn’t run away is because assuming it was an early model, an LB7, then it’s crankcase vent was open to the atmosphere, it wasn’t ducted back into the suckside of the engine like most, including our boats do.

Quakerstate and Penzoil were so terrible because they were paraffin based oils (genuine Pennsylvania crude) and the parrafin was condensed on any cooler spaces, like valve covers, but they have been gone for decades.
No modern diesel oil if changed when it should, will ever form any kind of sludge, you should never see that Quakerstate “protective film” on a Diesel.
https://books.google.com/books?id=zi...20film&f=false

[jimbunyard]

Originally Posted by Scubaseas

#86, Jimbunyard. You may want to look up "Pascal's Law" or "Pascal's Principle"

Why? Believe Pascal's principle has to do with pressure in a closed system, which an engine's lubrication system is not.

Originally Posted by a64pilot

The reason the Duramax didn’t run away is because assuming it was an early model, an LB7, then it’s crankcase vent was open to the atmosphere, it wasn’t ducted back into the suckside of the engine like most, including our boats do.

Quakerstate and Penzoil were so terrible because they were paraffin based oils (genuine Pennsylvania crude) and the parrafin was condensed on any cooler spaces, like valve covers, but they have been gone for decades.
No modern diesel oil if changed when it should, will ever form any kind of sludge, you should never see that Quakerstate “protective film” on a Diesel.
https://books.google.com/books?id=zi...20film&f=false

That's almost certainly the case, though depending on where the injector bodies were cracked (and thus the pressure differential in the crankcase) and the construction of the engine, the diesel could also have blown the seals out of the engine, allowing enough to escape to avoid a runaway. As it could also do on other engine designs.

It's not an experiment I wish to conduct.

Not positive, but pretty sure motor oils, synthetic or not, are all based on hydrocarbons, which if heated will still 'cook' and form gum deposits, especially at the 200F + temperatures modern engines run. This assumption is certainly borne out by the last valve cover I had off about a month ago, on a 2003 4L I-6 Jeep, shop maintained (with records) until I got it about 15000 miles ago. I've changed the oil 4 times since I've had it (castrol 20-50); the deposits were so stubborn that I left most of them alone. I plan eventually to play with different t'stats to get the temp below the factory-standard 210F operating temp, partly because of those cooked-on deposits and partly because operating at that temp just scares me. Old habits die hard.

[Scubaseas]

I'll take your word for it that you believe you can have a downstream pressure higher than the regulated line pressure.



Oil for a 2003 Jeep 4L is 10W30 that meets Chrysler MS6395, 5w30 in cold climates. Use the specified oil of the right viscosity and you'll have little if any sludge build up. Especially if the vehicle gets relatively short drive cycles, like under 30 minutes. Use the right oil and you won't have problems in the first place. This is hypercritical in automotive applications post around 2000.



Lowering the design operating temperature can lead to oil being too cold (which has it's own issues), the emissions not working right and water condensate/sludge build up inside the engine. I would bet the engineers at Chrysler may know more about it than anyone.