Yanmar Engine Troubles

[Guest]

I have a sea water cooled Yanmar 2GM20, approx 12 years old. It has recently started to smoke badly when under load, and spits engine oil out of the exhaust at a rate of about 1 litre every 3 hours. It seem to start, run and perform as normal otherwise.

Any suggestions as to the most likely cause?

 

[tr7v8]

Firstly what colour is the oil, if its black then it's excess burnt fuel, if as I suspect it's blue then you're burning oil.
Since it starts and runs OK I'd suspect a breater that's blocked and chucking oil into the combustion chamber. Only other thing could be a leaking oil cooler but prety sure that this Yanmar doen't have one.


Jim
----------

 

[jimboaw]

Engine oil out of the exhaust? Could you be mistaken and it is coming from the crankcase breather and into the intake manifold.? Whatever, my old 3HM35 raw water cooled suffered the very same symptoms. Turned out to be a head gasket was the root cause. A small amount of sea water had seeped into one cylinder and as you cannot compress water that had broken a ring. That led to excess crankcase pressure which blew the oil out. Like yours mine seemed to start and run normally until under load when 2 cylinders tried to do the work of 3 leading to thick black smoke. If this turns out to be the case be sure to examine the head and cylinder block for any pitting caused by the passing of salt water into the bore. mine resulted in a total rebuild. Good Luck.

 

[daveheaddon]

Similar problem with my old Volvo.

Black smoke mixed with water (making a black film on the water's surface) out of the exhaust. Turned out to be simply bad (low) compression and unburnt fuel. New gasket set and (while the head is off...and, at this time of year) reseat the valves.

Starts very well now and runs fine. No problems since.

I'm a diesel novice but it seems to me that these things are pretty straightforward to diagnose and fix. I went on a one-day course locally (£25) and now do everything myself. Some head-gasket work can be done in-situ and needn't mean expensive boatyard bills.

Dave

 

[Burnham_Bob]

I've had a look in the Yanmar workshop manual. There isn't an oil cooler, but there is an oil pressure relief valve which if the pressure gets too high should just let the oil flow back into the oil pan at the bottom. Presumably there must be some sort of breather but I can't find one on the drawings. The amount of oil you are talking about does seem to suggest a blocked breather. I had a Vauxhall Cavalier that covered itsekf in unburnt oil and all that needed was the breather cleaning. In case it helps, if you need info from the workshop manual let me know.

 

[snowleopard]

could be glazed bores and gummed-up piston rings allowing oil to pass. do you run the engine without load for battery charging? you don't say what colour the smoke is:

white: water getting into the system
black: incomplete combustion (overload, faulty injectors)
blue: oil consumption

 

[charles_reed]

have a look at the head.

In gradually increasing the capacity of the engine Yanmar left less and less room on the lands between cooling and oil runs in the head.

I've had exactly the symptoms you report and found that there was a little burn from cylinder, thro' oil return into the water jacket.
To resolve the problem I had 0.05mm milled off the head, the most you can take off before having to worry is about0.125mm (5 thou).

In fact the weak point on these motors is cylinder head gasket problems.

To check, carry out a compression test - but I'd suggest having the head off and replaceing the gasket.

One Yanmar specialist I know recommends doing just that as a prophylactic measure every 1000 hours running on commercial working Yanmars.