Yanmar 3GM30F engine, burning oil--Why? Can you help?

[Sputnik]

A cylinder leakage test is the only way to really identify where the oil loss is. All the preheater plugs or injectors are removed. Each cyl' is brought up to TDC with both valves closed. Compressed air is applied to each cyl' in turn and the blow-by assessed. To check eliminate piston blow-by a couple of CC's of engine oil is applied to the cyl' under test, this should provide a temporary seal and a reduction of blow-by until it passes by the rings into the sump. However, even this test is not totally conclusive, as you can have stuck/worn oil rings with a good compression/low blow-by.
The chances are glazed bores, with stuck/worn oil rings.
Removing the 'head will give you a clue as to the condition of the bores, and if glazed but not worn too much can be honed, and new rings fitted.
If you have time then removal/strip/inspection & repair scheme is the way to go. If you are on a tight on time then replacement is the only real option.
Neil

[Mike Banks]

Oil gets into the engine from two or three possible sources.

One--worn rings or glazed bore--or slack rings caused bvy an engine overheat.

Valve stem seals are worn, or deteriorated from an engine overheat.

Oil re-circulation device (a condenser for the oil fumes from the engine sump) is choked with carbon or just needs cleaning. Not all engines have them--but they can dump a lot of oil directly into the inlet manifold in one hit--

Solutions are obvious--use a fuel catalyst (there are several available) to burn off the carbon from the cylinder walls. Add to the fuel and thenn give the engine a good run. It takes time but it works.

Second is to rep-lace the valve stem seals, and often a proprietary simple rubber cap over the valve stem and covering the end of the valve guide will do it.

Clean ot thoroughly the oil sump recovery condenser. It looks like a metal box usually integrated in the valve rocker cover, with a vacuum hose going to the inlet manifold. and is used to get rid of engine blow-by by feeding it back into the inlet air. This is the one I would check first--it is the easiest to fix, but not all engines have them.

[BruceS]

Do a Google for "bon ami engine" !!
How hard does the engine work normally?
3000 hours is not many under 'good' conditions.

[mtarcher]

I had a 3gm30f with 7400 hrs...and experienced the same for the last 1500 hrs: starting with blue smoke, sometimes dying after startup or switching between forward and reverse. Lots of oil consumption. The blow by was getting worse over time (noticed with removal of oil cap on rocker cover while engine running). All were tattle tale signs of ring issue or worse. I used 30w instead of 15w-30 to stem the consumption...it helped marginally. Since in the Eastern Caribbean, I was about to try some 40w, thinking it would buy me some time before the eventual overhaul/replacement outcome. After experiencing a perforated heat exchanger that allowed water on top of cylinders, it was time to pull things apart to see what the options were. I discovered a cracked piston face on the #2 piston. Talking to 4 dealers who sell the Yanmar parts and engines, the consensus (100%) was that the 3gm30f (if it doesn't have piston sleeves) is not cost-effective to rebuild, unless you are willing to do all the labor yourself. Even then, you would be somewhere between $2k to 3K shy of the price of new. Don't forget that new includes heat exchanger, alternator, pumps, etc. That was my direction to go, and in fact, the 3YM30AE is going in this summer in Puerto Del Rey, PR.

[DeepFrz]

Oh my...

[a64pilot]

Originally Posted by BruceS

Do a Google for "bon ami engine" !!
How hard does the engine work normally?
3000 hours is not many under 'good' conditions.

Lord BonAmi thing was sort of a last resort for Radial aircraft engines largely during the war years, it was an attempt to scratch up the cylinder walls to get the rings to seat without doing a proper repair.
It's even in the Pratt & Whitney manual for the R1340, written likely in the 30's.
Really the only way to know what is going on is by pulling the head.
Any motivated person can overhaul a small Diesel, yes there is machine work you have to have done, but you can save a lot of money.

[sailorchic34]

Originally Posted by mtarcher

II discovered a cracked piston face on the #2 piston. Talking to 4 dealers who sell the Yanmar parts and engines, the consensus (100%) was that the 3gm30f (if it doesn't have piston sleeves) is not cost-effective to rebuild, unless you are willing to do all the labor yourself. Even then, you would be somewhere between $2k to 3K shy of the price of new. Don't forget that new includes heat exchanger, alternator, pumps, etc. That was my direction to go, and in fact, the 3YM30AE is going in this summer in Puerto Del Rey, PR.

Hum, I rebuilt My 3gm30F for $1200 total. $300 was for machining of which 2/3's was boring and installing a sleeve in the bad hole. The first gen 3gm's have sleeves, later during a value engineered retooling, sleeves were removed and cast in place, Piston size is off a bit between the two also. I had the sleeve installed as the other two holes were in new condition after 1100 hours. That is the other two holes mic'ed as new. Parts was about $700 of which 300 was two new mounts to replace the bad ones. Bearings are oddly inexpensive. Also spent $100 on a special tool, and rest on paint, oil, new oil tubing, rags, etc.

Mind you, I rodded the heat exchanger with a cleaning kit for a 22 rifle. (Perfect fit btw). I have also replaced the discharge elbow for $115 (ebay)

I rebuilt my water pump">raw water pump and have parts aboard to rebuild the pump again. When the cooling pump goes I'll rebuild that too for $25 (not with yanmar bearing and seals though). A standard OEM Hitachi alternator is about $100. Again not from yanmar.

I do agree that shop labor would make a rebuild by others pretty spendy. After 4 years and over 500 hours on my engine, it's still going strong.

[a64pilot]

I still maintain that done properly, an overhaul can be of higher quality than new, you can polish the crank finer and hold tighter clearances if you desire.
I used to hone drag bike cylinders by hand to .0005 for example.
The key here is what SC called value engineered, meaning of course how to maximize profits, not build the best you can, just build good enough. You can do better than that

You however can blueprint, polish and CC the combustion chambers, your labor is free, and it's fun building the perfect engine.

I plan on one day procuring a run out 4-JHE and overhauling it, then R&R it for the one in the boat, and sell the old one. I bet I can build the perfect motor that way for less than half a repower

[Cadence]

Originally Posted by DeepFrz

Oh my...

A dead horse and war stories.

[Hyrdflyr]

I brought a boat from Seward AK to Bellingham WA (1700 miles) that burned a quart of oil every 3 hours. Buy cheap oil. Had to pay $36 a gallon for Delo in Yakatat Alaska. OUCH! Crooks! Spent almost as much on oil as I did fuel. That said: oil burn is almost always rings and worn out liners or cylinder bores- hardly ever valve guides, although you could always hope....

[a64pilot]

On an old engine with few hours it's usually polished bores.
You have to have the cross hatching on a cylinder, oil is held in the cross hatching and this oil helps the rings seal. A polished bore won't hold oil, no seal and oil consumption occurs.
The way an old engine gets its bore polished is from infrequent use. During long periods of not being used the bores lightly rust, then the engine is run and the rust is cleaned off, repeat this cycle many times and the cross hatching is worn away and you have polished bores.
This is very very prelevant in small aircraft engines as the fleet flies not much anymore.
Glazing is similar in the result but different, the cross hatching in the bores get filled with a film or varnish from incomplete combustion usually from lightly loaded engines that don't get hot enough to burn off the fuel complexly. Sometime this glaze can be cleaned off with an aggressive detergent oil additive and running the engine hard, getting it up to full temp and high cylinder pressures.
Normally I'd unhesitatingly say put in a can of sea foam, or Marvel Mystery oil and run the snot out of it, however the 3GM30 engine it would seem has a history of piston breakage.

[Cadence]

I can not find I mentioned it. If eating oil, have something at hand to smother the air to shut her down. Turning off the fuel may not work since they can run on sump oil till coming apart.

[oleman]

Originally Posted by Diesel Bill

My oil burner was bigger and burned more oil than your's. Just kidding. I was on an unrep oil tanker (underway replenishment) coming back from an I.O. (Indian Ocean) deployment after 106 days at sea. Ship was USNS Hassayampa.
We were en route to Subic Bay P.I. and off the bottom horn of India. The guys in the E/R were thinking of cold beer and girls (damn sailors) and weren't watching the water level sight glasses on the boilers. We lost 2 large down comer tubes in the port boiler and feed water was dumping into the furnace. Stb. boiler was not getting feed water as all was going to lowest pressure which was port boiler furnace.
Bear with me, I'm getting to the point of this yarn in a moment. We were dead in the water with one boiler with flooded furnace and collapsed fire brick and other boiler dry fired with resulting sagged/sagging tubes. We had an old EMD 645 inline 8 cylinder gen set up in the bow of the ship. This worn out old relic would burn through 5 gals of lube oil in 4 hours. We only had a few drums of diesel oil on board so when the last of it was gone we started feeding it turbine oil as we had over a 1,000 gals of that on board. I took us over a week to do repairs and plug tubes to limp into Singapore. I wish that I had pictures of the smoke screen. The bow of the ship was invisible in the smoke for over a week.
By the way the EMD 645 is a 2 stroke just like a Detroit 6-71 on steroids.

A Chief Engineer that would allow his equipment to get into that state of disrepair should have been relieved on cause. The Captain/WHAT EVER THE MERCHANT MARINE CALLS HIM should also have been reprimanded.
I personally have no tolerance for inapt engineers anywhere in the USN.
I was on USS TRUXTUN(CGN-35) for 3 years once long ago.

[lancelot9898]

Originally Posted by Mike Banks

Oil gets into the engine from two or three possible sources.


Solutions are obvious--use a fuel catalyst (there are several available) to burn off the carbon from the cylinder walls. Add to the fuel and thenn give the engine a good run. It takes time but it works.

.

Can you list the names of some of these fuel catalyst? Seems like a good routine maintenance item?

[Diesel Bill]

Originally Posted by oleman

A Chief Engineer that would allow his equipment to get into that state of disrepair should have been relieved on cause. The Captain/WHAT EVER THE MERCHANT MARINE CALLS HIM should also have been reprimanded.
I personally have no tolerance for inapt engineers anywhere in the USN.
I was on USS TRUXTUN(CGN-35) for 3 years once long ago.

I agree with you completely. As the USNS Hassayampa, USNS Ponchatula and USNS Navasota were all ex navy Military Sea Lift Command ships and hand me downs from the U.S. Navy. And had the crap beat out of them before being handed over to M.S.C. and were in deplorable condition as received. I served on all 3 ships and it was a constant struggle to keep them on mission.
May I suggest we keel haul the navy personnel responsible for not maintaining the vessels prior to their turn over.
I also was assigned to USNS Spica, AFS-9, This was the ex HMS Tarbatness
was given to MSC as part of the war dept repayment. This ship also had the snot run out of it before the turn over. Plus it was built with Mirlees auxillaries which no more need be said if you are at all familiar with English sports cars with Lucas electrics.
I could go on and on but I think it best to shut up before I offend any sensitive types, and no offence to our limey brothers, love ya all.

P.S. Thank you for your service.