Yanmar 3GM30F White Smoke

[Jollymon352]

Greetings,
I have a Yanmar 3GM30F in a 1999 Beneteau Oceanis 352. The engine is original to the boat and has 347 hrs. I motor at 2500- 2800 rpms and at anchor I no load idle at 1500 rpm to heat shower water and or charge batteries.

Yesterday I was motoring @ 2500 rpm when the engine started making a knocking sound similar to the sound of a rod knocking. A large cloud of white smoke was belching from the exhaust. I lowered the rpms to 1800 rpm's the rattling and smoke stopped. I eased the trottle back up to 2500 after a few moments the rattling and white smoke started again.
Today at the dock I no load trottled up to 3600 rpm. After about a minute the knocking started as well as a thick production of white smoke. Again I lowered the trottle to 1800 rpm and the symptons stopped. There was an oily film on the water.

Idling and at low loaded and no load rpm's the engine sounds perfect.

Does anyone have any ideas or advice?
Thank you, in advance for your help.

John (Jollymon)

[djmarchand]

Sounds like a blown head gasket letting coolant into the engine combustion chamber. The knocking is caused by the water flashing to steam violently and the white smoke is the steam that results.

Check your crankcase for antifreeze in the oil. At low speed the leak can be into the cooling system, but as the speed increases the pressure is enough to send it the other way into the combustion chamber.

Also open the "radiator" cap and look for bubbles that increase when you rev up the engine.

Either effect is a sure sign of a blown head gasket.

Less likely but possible because of the oil sheen are bad injectors.

David

[Jollymon352]

There is no water in the oil or bubbles in the heat exchanger. The exhaust is smoke. Steam will quickly disapate. The smoke lingers and drift for an extended period.

Thank you for your imput.

[DeepFrz]

White smoke is a sign of water vapor or fuel that has been atomized but not burned. The water vapor may be present in the fuel or water may be leaking into the cylinder from the cooling system. Air in the fuel can also cause white smoke.

[Ex-Calif]

Hard to describe but what does the smoke smell like?

What is ambient temperature/dewpoint?

It is hard to believe that this is not water vapor. It will smell like dirty boiling water. If the ambient temperature is low and dew point fairly high it may not dissipate quickly.

With very limited info I would throw a guess at a failed exhaust valve spring. At higher RPM the valve floats, the flame front enters the exhaust riser and boils the raw water.

Just a guess. Unless you have pretty good skills and tools I would get a mechanic involved.

One thing for sure loud knocking is bad. This indicates either early ignition, hydraulic locking or some other defect that can really damage connecting rods etc...

[Jollymon352]

The humidity is 57% The dewpoint is 59% The tempature is 75 degrees.
It is definitely smoke and I agree based on some of the other threads previously posted that it is atomized but unburnt diesel.

[Chief Engineer]

Blown injector tip allowing fuel to pour into cylinder. Would be my first impression.

Next is headgasket.

Unless you have the proper diagnostic tools, I would not run the engine any mo'

[Jollymon352]

Thank you, All.
Can I replace the injector nozzle or should I replace the injector assembly?

[djmarchand]

If your knocking symptom occurs in neutral, rev the engine to that speed and then crack each injector nut. The one where the knocking diminishes is the bad one, as I doubt that all three went bad all of a sudden.

Replace the entire injector assembly. About $125 each. Not worth rebuilding. Make sure that you also buy the crush washer on the bottom.

You can also pull all three and have them spray tested. You may have gotten water in your diesel which blew out the tip(s).

David

[Sailmonkey]

I've seen this before in (i think) a 2gm20F. If the the 3gm has the same pre-combustion chambers, it's possible that the chamber it's self has broken and the injector is no longer spraying into the chamber but rather the cylinder. Remove the head and check, it's really not all that bad of a job.

[GordMay]

Diesel SMOKE COLOUR AND ITS CAUSES:

WHITE SMOKE - Misfiring cylinders; water in fuel; air in fuel; water in cylinders (blown head gasket, cracked head or liner); lack of compression.

BLACK SMOKE - Restricted air flow ( dirty / obstructed air filter; plugged exhaust; restrictions in exhaust system; defective turbo / supercharger); Overload; Improper injection (poor atomization, injector dribble, late injection)

BLUE SMOKE - Worn or stuck piston rings; worn valve guides and stems; high crankcase pressure; worn / supercharger oil seals.

[Jollymon352]

I am going to pull the engine to change a leaking rear main seal. My plans are to perform this work while the boat is at the dock.

Am I setting myself up for disaster?

[Drumroll30]

Changing your rear main seal won't solve the white smoke problem. Your cruising speed at 2500 to 2800 is good but idling at 1500 for battery charging and heating water isn't very good for the engine. When at anchor and desperate for charging (I have a 12 volt fridge) I put the engine in reverse while its running to keep it under load. Are you sure that this engine only has 347 hours on it? I have a 2GM20F with around 1500 hours and it has never given me any problems.

[Jollymon352]

The engine has been leaking oil for the past year. I have decided that while changing the injector that I was going to change the main seal also.

[Westbrook]

My Yanmar 3GM30 had the same white smoke problem several years ago. Signifies not electing a new Pope, but unburned diesel fuel, probably due to a faulty injector.

Releasing the pressure on each cylinder one at a time should identify the faulty injector.

Best deal on injectors at B&D Injection Service, Inc.: Fuel Injectors, Temple Hills, MD, B & D Fuel Injection Service is the outstanding east coast operation for diesel pumps, diesel and gas injectors, and turbochargers.. Recently rebuilt two for me at $92 apiece.