New twist on Yanmar issue?

[sailorchic34]

With the engine idleing, open and remove the oil fill cap and observe for excess crankcase pressure or "lots" of grey smoke. If there isn't excess pressure and no grey smoke then your ring are most likely good. Also check that the crankcase breather is clear and not blocked.


I will say that my yanmar 3gm30f did use 1 quart in less then 12 hours. That turned out to be broken ring lands on one piston. Yanmar in 1994 had a batch of pistons that were not up to spec. You can read about my summer of discontent here -> http://www.cruisersforum.com/forums/...ar-107705.html


With that said, if it starts easy, and there isn't any pressure or grey smoke with the oil fill open and engine running, odds are the rings are good. If you do get pressure relief and smoke then odds are you have at least one hole with at least a broken oil control ring.



Another area to check is the external oil line just in front of the starter and behind the oil filter. The oil lines have a habit of rusting there and leaking. Yanmar has a copper replacement for not too much money. If the oil line is bumpy, replace...


A blown head gasket could cause excess oil consumption. As would worn valve guides on the exhaust valves. That last would be remote.

[Cheechako]

Originally Posted by sailorchic34

With the engine idleing, open and remove the oil fill cap and observe for excess crankcase pressure or "lots" of grey smoke. If there isn't excess pressure and no grey smoke then your ring are most likely good. Also check that the crankcase breather is clear and not blocked.


I will say that my yanmar 3gm30f did use 1 quart in less then 12 hours. That turned out to be broken ring lands on one piston. Yanmar in 1994 had a batch of pistons that were not up to spec. You can read about my summer of discontent here -> http://www.cruisersforum.com/forums/...ar-107705.html


With that said, if it starts easy, and there isn't any pressure or grey smoke with the oil fill open and engine running, odds are the rings are good. If you do get pressure relief and smoke then odds are you have at least one hole with at least a broken oil control ring.



Another area to check is the external oil line just in front of the starter and behind the oil filter. The oil lines have a habit of rusting there and leaking. Yanmar has a copper replacement for not too much money. If the oil line is bumpy, replace...


A blown head gasket could cause excess oil consumption. As would worn valve guides on the exhaust valves. That last would be remote.

Yes... OP think about the gasket possibility, I mentioned it early on in this thread, IIRC there is an oil passage in the block near the cylinder, oil could leak into the cylinder from that via a bad head gasket.

[laika]

I made a post on CF a few years ago with the same oil consumption symptoms on my 3GM30F (minus the tranny issue). Got help and input by many of the same fine folks on this thread.

I've found over the last couple years that if I keep the RPMs below 2700 I do not burn any significant amount of oil. BUt if I open it up for any length of time, the oil consumption goes way up. Engine runs great and doesn't smoke at any RPM.

[Gr8tewhite]

Well hopefully we will have an answer soon enough. I have scheduled a Yanmar certified tech to come take a look the second week of April. Thank you all for the responses. I will keep everyone posted.

[roverhi]

The classic cause of oil consumption in an otherwise normally running engine is valve seals. Bad seals allow the engine to suck in oil from around the valve shafts without decreasing the compression much and effecting performance. The 3 GM has a history of other problems on some engines so may not be the cause. If it is the guides, it's about the easiest thing to fix and easily done by an owner with the only fancy tool required being a torque wrench. Rule out the possible causes but if you are still stumped pull the head and take to a machine shop for a valve job and new seals. While the head is off you can inspect the engine bores for signs of piston and/or ring issues and will readily see if it's a head gasket problem.

If there is any sign of oil in the bilge, the cause is probably the external oil line that runs under the exhaust manifold and around the back side of the engine. The original pipe is steel and quickly rusts if it gets salt water on it from the exhaust flange. Replacement is cupro nickel, I think, so shouldn't suffer the corrosion issues of the original. Replacement requires removal of the starter and access to the sides of the engine. Can be done in place in most boats but way easier with the engine sitting on the cabin sole. I replaced mine as a preventive maintenance measure when I had the engine out. The old one was nearly rusted through with less than 300 hours but more than a decade in place.

[a64pilot]

I’m going to argue a little here, excess oil consumption through valve seals is, well I have never seen it.
I have seen very often that worn valve seals will cause a lot of blue smoke when an engine is first started, but goes away in a couple of minutes.
That is from the oil leaking into the combustion chamber overnight and of course burning off when the engine is started.
Yes there is oil consumption, but it’s not much.
Many engines used or not even have valve seals, and I’d bet many still don’t. People just knew they smoked a little on start up I guess.

[Cheechako]

It was pretty common "back in the day". Not so much now though.

[a64pilot]

I know these are not aircraft engines, but just to put things into perspective, read the following from Lycoming which manufacturers likely most of the aircraft piston engines in existence.
https://www.lycoming.com/content/tips-hangar

[Gr8tewhite]

A not insignificant rate of consumption seems to be the norm. I could live with that, especially since there is no blue smoke on start up, or smoke in general for that matter. Unfortunately, I’ve still got the oil slick when shifting into reverse to contend with.

[Compass790]

Originally Posted by Gr8tewhite

A not insignificant rate of consumption seems to be the norm. I could live with that, especially since there is no blue smoke on start up, or smoke in general for that matter. Unfortunately, I’ve still got the oil slick when shifting into reverse to contend with.

There is nothing normal about a quart of oil in 12 hrs on that size engine especially IF the rate of consumption suddenly increased.
Wierd the reverse symptom. Are you absolutely sure it's engine oil in the slick & not diesel? You could have 2 problems at once.
I know a bloke that puts 20 litres of oil in his bulldozer daily if he's working but he freely admits his engine is worn out. Has been doing that for years but I wouldn't want to be anywhere near it whilst it's running

[Compass790]

Originally Posted by Gr8tewhite

Well hopefully we will have an answer soon enough. I have scheduled a Yanmar certified tech to come take a look the second week of April. Thank you all for the responses. I will keep everyone posted.

Hope you can be there when Yanmar certified tech comes. Best to witness compression test. Sorry just realised repeated what danielamartindm had posted earlier in post 12 re slick in reverse.

[a64pilot]

Originally Posted by Gr8tewhite

A not insignificant rate of consumption seems to be the norm. I could live with that, especially since there is no blue smoke on start up, or smoke in general for that matter. Unfortunately, I’ve still got the oil slick when shifting into reverse to contend with.

There is definitely an “issue” and if your plan is to keep the boat forever, you need to address it, eventually.
However as the other poster said, pretty much whatever is wrong will almost certainly result in an overhaul, and like the bulldozer another poster brought up, you May have years, but maybe you should start saving and planing on when to overhaul.
But if it’s just wear, you may have a long time before it becomes absolutely necessary.
Almost always a top overhaul of a Diesel becomes necessary when they either smoke excessively or become hard to start.

I had a 220 Mercedes Diesel many years ago, we used to joke, fill it up with oil and check the fuel.
Thing would burn almost a quart per fill up, and that was considered normal, but it also had one piece iron oil control rings too.

There have been several studies conducted that indicate that oil usage actually decreases cylinder and ring wear significantly, cause of course they are well lubricated.
Mine burns a half quart every 100 hours, and I like that.

[kmacdonald]

Burning a quart every 12 hours is a lot. That's like a car burning a quart every 600 miles (at 50 mph). That's why I think it's leaking , maybe at the oil cooler if it has one.

[a64pilot]

A quart in 12 hours is a lot.
One thing that could aggravate it is a clogged oil separator in the valve cover.
It could also be an oil cooler, but to never get water in the oil is hard to believe from a bad cooler.

[hellosailor]

Seafoam is not magic, it is actually just a slickly packaged version of what every old mechanic used to do: Pour yesterday's coffee into the engine.

As the coffee, which is really water, gets into the cylinders it superheats and flashes into steam, which is a damned good way to scour carbon buildup and anything else sticking the rings or cylinder walls.

What Seafoam does (read the MSDS) is add some isopropanol (more cleaning) and light machine oil along with naphtha (fuel base stock) so that while it scours, the extra oil also promptly relubricates.

Dunno, I like the power of yesterday's coffee dregs more.(G)

But if the OP can't easily run a compression test, then do a leak-down test instead. Remove the glowplugs or injectors, hand rotate the engine until all four cylinders are halfway down. Pour fuel into each cylinder, go away for a while. When you come back check the level--all four should be leaking down slowly and evenly, or else you've got cylinder/ring problems.

Not as fast as hooking up an air compressor, but requires nothing that's not already on board.