Low oil pressure-Heavy Blow by causes oil loss-and Smoke!

[j.g.evans]

I once identified poor compression when I was away from civilization, i.e. Bahamas, by seeing if a warm engine would start on one cylinder at a time using the compression release levers. There was no compression in one cylinder due to blow by. I also found oil leaking around the pan due to too much blow-by pressure.

[Ninedotsix]

I have read this thread with get interest, since I recently experienced same symptoms with my Yanmar 2QM15.
The first burst of blue oil smoke came when leaving dock for what turned out to be 13 day cruise, island hopping from Deltaville to Baltimore and return.
Lots of blow by at the filler cap, but not detected at the crankcase vent, or the dipstick.
Burned 1-1/2 gallons of oil on the trip, and worried about it a lot.
Smoke not always visible, but if motor sailing downwind, would definitely smell the tell tale sweet burnt oil smell.
In the end, after much gnashing of teeth, decided to dive in and check head gasket, rings, valve guides, stem seals, etc.
Found the exhaust valves badly fouled, with one burned around the edges.
Seating of exhaust valves was not evident.
Rings looked fine, and the end gap on rings was at the tight end of the tolerance range, and head gasket had been sealing properly.
Pistons miked out to be within the middle of tolerance range.
Valve guides (all) were badly worn and with that I can believe the stem seals would leak, so I think the condition of the guides started a cascade, so that with burning oil the build up on exhaust valve seats let gas blow into the intake passages passing the rings on upstroke, and all this combined with oil sucking through stem seals on top end, into the intake then into the cylinders.
I went ahead and cleaned the head, lightly honed cylinders, replaced the guides, valves and stem seals, put in new rings, and changed rod bearings. Naturally, used all new gaskets.
I was able to do this work in frame without removing the engine.
I've got a long reach, but this 2 cylinder was at the end of my reach underneath to put the pan back in place. A 3 cylinder would have been out of reach, I do believe.
Anyway, on startup there was no blue smoke, and no blow-by.
I need to go back and run the boat around the harbor some, to get myself comfortable that it will run indefinitely.
I agree with the assessment in the early replies in this thread that at 6500 hours, you need to "decarbonize".
I note that the 2QM15 manual says to check rings, lap valves and rod cap bearing check every 1,000 hours.
Wonder what the 3 cylinder manual says?
Cheers ~ 9.6

[Ken Fry]

Originally Posted by Ninedotsix

I've got a long reach, but this 2 cylinder was at the end of my reach underneath to put the pan back in place. A 3 cylinder would have been out of reach, I do believe.

Wow. Great luck with that. Engineers try to design things so that the oil pan will just almost come off, but not quite. Then you jack up the engine a little, only to find that the oil pickup is now hanging up...

I'd have to think that on your engine the valve clearances had closed down, causing the burned one to be held off its seat. As soon as that happens, things go downhill very fast... even to include valve heads dropping off into cylinders. As a general rule, valves in such bad shape are not found with a lower end in such good shape.

It sounds like you already know the following, but pretty soon after putting in new valves, you will want to check tappet clearances, which will usually close up as the valves seat in.

Not to sound like your grandma here... but had you been regularly checking valve tappet clearances?

Plenty of work, but you now have a very nearly new engine! Bravo. How many hours were on yours?

[Ninedotsix]

Sorry, I can't tell you hours, but it was last reworked in 2006.
That was a sobering teardown, b/c I found some SOB had removed the pads from the valve stems to make the valves operate with overground (too deep) seats, and then shimmed under the springs with copper shims.
What a mess.
I had the shop put in seats and guides, and provided new valves, pads, retainers and collets.

You are right to mention checking clearance, and I'll add to that: a recheck of the bolt torque at 50 hours, per Yanmar.

I need to be more careful about cooling water on while cranking, as there was water in the oil, but I think it was from last time or two of cranking tto long before deciding I needed to tear down for rework.

The throttle position on this engine must be set high to start, then immediately brought down. I worry that the governor is not limiting enough, and have gotten parts to install flywheel sensor and tachometer.

Anyway, thanks for your comments, rocker arm clearance is definitely a necessary periodic check.

~ 9.6

[wingssail]

I've done quite a bit more testing and inspecting. Haven't gotten into the injector removal or compression check yet, due to holidays and activities.

The engine is operable within some restrictions (2500 or under & watch the exhaust). We'll get to the compression check next week or so.

Findings:

• Oil pressure is on low side of normal but sufficient. A wire to the gauge was broken.
• Blow-by. None at the breather pipe under 3000rpm. At 3000 it GUSHES OIL, (no gases), HEAPS of oil, which accounts for the blue smoke. It's going straight into the air cleaner.
• The oil itself is clean and has good viscosity, no indication of dilution or water.
• The crankcase breather pipe runs from the front of the engine on the cover of the oil pump (see picture), not from the valve cover.
• I still have no symptoms which indicate ring or valve issues, no strange sounds, no rough running or starting issues.

At his point I am thinking there is some issue with the oil system, possibly the regulator valve in the oil pump itself. I've had several unexplained oil pressure issues in the past few years, maybe they are all related. These parts of the oil pump are not serviceable, according to the manual.

I am going to proceed with the compression tests unless someone more knowledgeable than I talks me out of it, but right now I think there is a new oil pump in my future.

[Scubaseas]

Inquiring minds want to now and I am sure you looked at these but just asking for sh*ts and giggles:

What year is the engine and it's just a 3JH(?) Non turbo?

Does the dip stick have an o-ring on it? Without knowing what your crankcase pressure is your problem may be as simple as the dipstick o-ring is worn out. I kid you not.

I assume you checked the oil level with the engine off and rested for 5 minutes or so?

Air cleaner is not clogged where the vent hose goes into it? Or the hose from housing to filter is not clogged?

A cheap olde fashioned fuel pump pressure gauge (like https://www.amazon.com/Carburetor-Va...ts_id=15707421 ) would work as a manometer. Measure at the vent hose, then measure at the dip stick both at idle and at 2500 and at 3000rpm. Should be the same pressure between the two locations but the pressure will rise as the engine speed does. If not remove the housing covering the injection pump gear and clean. Ditto hose to air cleaner.

Got a picture of the top of the engine/Valve cover? Picture of air cleaner with hoses?

[wingssail]

Originally Posted by Scubaseas

Inquiring minds want to now and I am sure you looked at these but just asking for sh*ts and giggles:

What year is the engine and it's just a 3JH(?) Non turbo?

The engine is a 1994 3JH2E (non turbo)

Does the dip stick have an o-ring on it? Without knowing what your crankcase pressure is your problem may be as simple as the dipstick o-ring is worn out. I kid you not.

The dipstick has a sort of plug about an inch long which is intended to seal the top of the tube, Since this issue arose I inspected that and found it worn and much diminished in size. I have created a new seal using (don't laugh) Flex tape which seems to have a tighter fit.

I assume you checked the oil level with the engine off and rested for 5 minutes or so?Yes

Air cleaner is not clogged where the vent hose goes into it? Or the hose from housing to filter is not clogged? I have inspected this hose and the air cleaner and have blown through it. It is not blocked, and in fact this is the route which the oil takes in route to being burned and causing smoke. The source is what is under question.

A cheap olde fashioned fuel pump pressure gauge (like https://www.amazon.com/Carburetor-Va...ts_id=15707421 ) would work as a manometer. Measure at the vent hose, then measure at the dip stick both at idle and at 2500 and at 3000rpm. Should be the same pressure between the two locations but the pressure will rise as the engine speed does. If not remove the housing covering the injection pump gear and clean. Ditto hose to air cleaner.
Well, I have not done that, however I have removed the breather hose, and the dipstick and felt the amount of blow-by at the two places and it is pretty much nil, until I hit 3000RPM or so and then the breather gushes oil like a Texas oil well, at which point I discontinued the experiment.

OK, I get that, now think about this, now that I have your attention on it. The oil pump is within this gear cover. Looking at the manual it appears that there is a pressure relief valve which dumps oil back to the crankcase when the pressure exceeds a factory set limit.(the manual says it is not user serviceable and cannot even be disassembled). So what if, when the pressure gets too high, instead of dumping the oil through a passage into the crankcase it allows, because of a crack a blown gasket or something, it to flow into the inside of the gear cover, where the oil breather is?

That is what I am going to look for but getting that cover off means removing the whole front plate of the engine, including the crank pully.

Got a picture of the top of the engine/Valve cover? Picture of air cleaner with hoses? Yes

Thanks, Scubaseas. Maybe we are zeroing in on this thing, although I've thought that before.

[Scubaseas]

OK, I get that, now think about this, now that I have your attention on it. The oil pump is within this gear cover. Looking at the manual it appears that there is a pressure relief valve which dumps oil back to the crankcase when the pressure exceeds a factory set limit.(the manual says it is not user serviceable and cannot even be disassembled). So what if, when the pressure gets too high, instead of dumping the oil through a passage into the crankcase it allows, because of a crack a blown gasket or something, it to flow into the inside of the gear cover, where the oil breather is?

Thanks for the info and pictures. A 3jh and 3jh2E are slightly different beasts from a crank case venting perspective.

There are two pressure relief valves, One on the oil pump itself which vents out the nut that holds the relief plunger in place and there is one in the oil filter housing. If you pull off the nut that holds the pressure relief valve in the filter housing and take out the spring you can take out one of the small shims. This will lower the pressure at speed by about 5psi. This would allow the filter valve to blow off and dump into the oil pan before the pump relief valve blows off. Having a stuck relief valve (steel inside an aluminum housing) get stuck due to a worn bore seems to be a fairly common Yanmar complaint and it looks like they used the filter housing for a lot of engines. You should be able to easily slide the filter housing relief valve all the way in and out with your pinky. If the bore is worn out (and you can visually check this) toss the housing. It's highly unlikely the oil backing up is a fault in the oil pump relief system which is a steel on steel piston/housing set up. I would pull the outermost cover off the oil pump cover. This would let you check for sludge build up which is a possibility with your symptoms. You could also check for sludge by puling off the valve cover and may as well adjust the valves while there. But check the filter housing relief valve getting stuck as that seems the most probable cause and seems pretty common. Or just replace the whole oil filter housing prophylactically.

You could always use the vent on the top of the valve cover (like the 3JH uses) and that would probably eliminate the issue also. Hard to say without crank case pressure numbers though.

[Scubaseas]

Sorry hit send too soon. Your question hypothesis is can the oil pump relief valve blowing off allow oil to be pumped up the crank case vent hose? I would say yes, that is possible especially if you have elevated crank case pressure due to normal age/wear and tear. Sometimes the way Yanmar designs stuff baffles me. Why they changed the crank vent system I have no idea but from a JH3 to a JH3-2E . You could always run the hose to a can and pour it back into the engine as needed or put a can above the engine, run the hose into that and run a return line back to the block off plate on the valve cover. With over 50 years as a mechanic you see a lot of cleaver solutions to problems. But the best way is to fix it proper. I doubt you need to pull the oil pump itself or the timing cover. Pull apart the oil filter housing relief system and check there.

But I would be concerned about sludge build up in the engine as that could also be a cause of your symptoms. Unless you have had it off recently I would recommend taking off the valve cover and have a look to see if you have gunk build up. Can't hurt and is easy to do. If you haven't adjusted the valves in the last 100 hours having the cover off is the time to do it.

[Scubaseas]

The hole below the nut and directly below the shaft is where oil would spray out/vent off on relief valve opening. I could see this spraying oil at the vent hose and giving your symptoms. But it's more likely the relief valve is opening on the oil pump due to the relief valve at the filter not opening. Fix the filter housing relief valve and oil pump will probably work OK.

[wingssail]

Originally Posted by Scubaseas

Sorry hit send too soon. Your question hypothesis is can the oil pump relief valve blowing off allow oil to be pumped up the crank case vent hose? I would say yes, that is possible especially if you have elevated crank case pressure due to normal age/wear and tear. Sometimes the way Yanmar designs stuff baffles me. Why they changed the crank vent system I have no idea but from a JH3 to a JH3-2E . You could always run the hose to a can and pour it back into the engine as needed or put a can above the engine, run the hose into that and run a return line back to the block off plate on the valve cover. With over 50 years as a mechanic you see a lot of cleaver solutions to problems. But the best way is to fix it proper. I doubt you need to pull the oil pump itself or the timing cover. Pull apart the oil filter housing relief system and check there.

But I would be concerned about sludge build up in the engine as that could also be a cause of your symptoms. Unless you have had it off recently I would recommend taking off the valve cover and have a look to see if you have gunk build up. Can't hurt and is easy to do. If you haven't adjusted the valves in the last 100 hours having the cover off is the time to do it.

Good feedback! I can check the oil filter relief valve much easier than the oil pump relief valve so I will do that first.

Sludge is not a problem in this engine. The valve cover has been off recently and it is clean. The pan has also been off six months ago when we were changing the rear main oil seal and there was no sign of any black sludge there or anywhere. The photo below is what is visible through the oil fill cap in the rocker arm cover, you can't see much but the whole rocker arm assembly looks like that. I do agree about the need for adjusting the valves, they have not been done recently.

About the oil filter pressure relief valve, if that was stuck or sticking (and I hope to get it out in a few days to see how it operates) are you saying that oil flow will back up to the gear case where the breather pipe is and then out the breather pipe? And secondly, why am I not seeing a spike in the oil pressure?

OK, is this it? The pressure relief valve in the oil filter housing is preventing an increase in the pressure beyond it (in the gallery) but it is not properly dumping the excess oil into the crank case?

[wingssail]

Originally Posted by Scubaseas

Sorry hit send too soon. Your question hypothesis is can the oil pump relief valve blowing off allow oil to be pumped up the crank case vent hose? I would say yes, that is possible especially if you have elevated crank case pressure due to normal age/wear and tear. Sometimes the way Yanmar designs stuff baffles me. Why they changed the crank vent system I have no idea but from a JH3 to a JH3-2E . You could always run the hose to a can and pour it back into the engine as needed or put a can above the engine, run the hose into that and run a return line back to the block off plate on the valve cover. With over 50 years as a mechanic you see a lot of cleaver solutions to problems. But the best way is to fix it proper. I doubt you need to pull the oil pump itself or the timing cover. Pull apart the oil filter housing relief system and check there.

But I would be concerned about sludge build up in the engine as that could also be a cause of your symptoms. Unless you have had it off recently I would recommend taking off the valve cover and have a look to see if you have gunk build up. Can't hurt and is easy to do. If you haven't adjusted the valves in the last 100 hours having the cover off is the time to do it.

Good feedback! I can check the oil filter relief valve much easier than the oil pump relief valve so I will do that first.

Sludge is not a problem in this engine. The valve cover has been off recently and it is clean. The pan has also been off six months ago when we were changing the rear main oil seal and there was no sign of any black sludge there or anywhere. The photo below is what is visible through the oil fill cap in the rocker arm cover, you can't see much but the whole rocker arm assembly looks like that. I do agree about the need for adjusting the valves, they have not been done recently.

About the oil filter pressure relief valve, if that was stuck or sticking (and I hope to get it out in a few days to see how it operates) are you saying that oil flow will back up to the gear case where the breather pipe is and then out the breather pipe? And secondly, why am I not seeing a spike in the oil pressure?

OK, is this it? The pressure relief valve in the oil filter housing is preventing an increase in the pressure beyond it (in the gallery) but it is not properly dumping the excess oil into the crank case?

PS, Oil does not "spray' out that breather tube (at the oil pump). When I removed that hose while running at 3000 RPM, I got, in about .5 seconds, about a cup of oil which pumped 4 feet across the boat and onto me, the cabin, the settee, and the upholstery. When I said it is a gusher, I wasn't kidding.

[Scubaseas]

About the oil filter pressure relief valve, if that was stuck or sticking (and I hope to get it out in a few days to see how it operates) are you saying that oil flow will back up to the gear case where the breather pipe is and then out the breather pipe? And secondly, why am I not seeing a spike in the oil pressure?

OK, is this it? The pressure relief valve in the oil filter housing is preventing an increase in the pressure beyond it (in the gallery) but it is not properly dumping the excess oil into the crank case?

Pretty much yes. The oil pump relief valve rarely opens but if the relief valve in the filter housing is stuck then ALL the excess pressure will get dumped out the oil pump relief valve. Which will spray it out the small hole pictured and probably almost straight at the vent hose. I can't tell you how many times engineers have been cursed at by mechanics. The pump is a big pump for a 3 cylinder engine (one size trochoid fits all) and it makes way more pressure and volume than you need. This is normally regulated via the pressure relief valve on the oil filter housing and dumps excess pressure and volume via a 13mm (approx.) passage back to the oil pan at the filter area. I can see why they would have two relief valves if they were trying to reduce the oil line pressure to a turbo or oil cooler but Yanmar seems to use this set up on a LOT of their engines. Most applications have one relief valve. Putting a crank vent hose on top of a pressure pump relief valve just strikes me as dumb but as long as it works it works. In your case it ain't working. The earlier versions of the 3JH took the vent hose off the top of the valve cover and through a baffle but I digress. Yes you are seeing oil sprayed into the hose because the oil pump relief is doing all the work. And you're not seeing a spike in oil pressure since the filter and the oil pump are set to about the same pressure. You can adjust the filter one so it can be slightly below the oil pump one. Specs are buried in the manual. But normally the filter dumps the excess oil pressure and volume back to the oil pan and the filter relief pressure is set a couple of pounds below the oil pump pressure relief setting.

If you have the shop manual look up the oil filtration system and oil pressure relief valve. It's covered pretty well there along with a flow chart on the oiling system. Your hypothesis is probably spot on but you'll need to look at the filter housing relief system to see if that's the problem and proof it out.

Insides look clean/fine. If you had sludge you would see it on the rocker arm.

Another poster and I went over this subject of pressure reliefs in depth a while ago. Either I'm telling it right or Jim Bunyard is. To each his own. Your choice whom to listen to.

[wingssail]

Originally Posted by Scubaseas

Pretty much yes. The oil pump relief valve rarely opens but if the relief valve in the filter housing is stuck then ALL the excess pressure will get dumped out the oil pump relief valve. Which will spray it out the small hole pictured and probably almost straight at the vent hose. I can't tell you how many times engineers have been cursed at by mechanics. The pump is a big pump for a 3 cylinder engine (one size trochoid fits all) and it makes way more pressure and volume than you need. This is normally regulated via the pressure relief valve on the oil filter housing and dumps excess pressure and volume via a 13mm (approx.) passage back to the oil pan at the filter area. I can see why they would have two relief valves if they were trying to reduce the oil line pressure to a turbo or oil cooler but Yanmar seems to use this set up on a LOT of their engines. Most applications have one relief valve. Putting a crank vent hose on top of a pressure pump relief valve just strikes me as dumb but as long as it works it works. In your case it ain't working. The earlier versions of the 3JH took the vent hose off the top of the valve cover and through a baffle but I digress. Yes you are seeing oil sprayed into the hose because the oil pump relief is doing all the work. And you're not seeing a spike in oil pressure since the filter and the oil pump are set to about the same pressure. You can adjust the filter one so it can be slightly below the oil pump one. Specs are buried in the manual. But normally the filter dumps the excess oil pressure and volume back to the oil pan and the filter relief pressure is set a couple of pounds below the oil pump pressure relief setting.

If you have the shop manual look up the oil filtration system and oil pressure relief valve. It's covered pretty well there along with a flow chart on the oiling system. Your hypothesis is probably spot on but you'll need to look at the filter housing relief system to see if that's the problem and proof it out.

Insides look clean/fine. If you had sludge you would see it on the rocker arm.

Another poster and I went over this subject of pressure reliefs in depth a while ago. Either I'm telling it right or Jim Bunyard is. To each his own. Your choice whom to listen to.

Thank You

[Scubaseas]

OK, is this it? The pressure relief valve in the oil filter housing is preventing an increase in the pressure beyond it (in the gallery) but it is not properly dumping the excess oil into the crank case?

PS, Oil does not "spray' out that breather tube (at the oil pump). When I removed that hose while running at 3000 RPM, I got, in about .5 seconds, about a cup of oil which pumped 4 feet across the boat and onto me, the cabin, the settee, and the upholstery. When I said it is a gusher, I wasn't kidding.

Based on what you are telling me, yes I would look to see if the oil filter housing pressure relief valve is sticking. If you look into the bore after the spring and plunger are out and see an elliptical shinny spot in the bore I would toss the housing. The over pressure and voulme normally dump back to the crankcase at the oil filter housing.

I could tell you a lot more if you had a pressure reading of the crank case. But think of a pea shooter. Now fill up your oil vent hose with a cup of oil and shoot it at about 2PSI or even more as the oil "slug" in the hose is blocking the vent and you are pumping it up until..... QED. Or watch how a percolator coffee pot works. I bet you could not design it to do this if you tried and I am sure the look on your face when it happened was priceless. You can't make this stuff up and it'll be a great story over a beer at the bar/beach.

If you feel no pressure with your thumb over the hose the crank pressure is probably OK. Most people can feel 1/2psi or so. But to measure blowby you need either a leakdown tester and an air supply (and know how to use it) or a manometer to measure how much pressure you are building up.