Yanmar 2GM20F - oil looks bad after 20 hours

[mcaswell]

I last changed my engine oil in June. Because it was pretty bad looking (black, instead of that nice honey color), I actually did two oil changes to help "flush" system clean. Since then, I've only put about 20 hours on the motor, and when I checked the oil a few days ago, it's black again.

Obviously I'll be doing another oil change soon, but is this a symptom of a particular engine problem?

--Michael

 

[Bill Murray]

It's a diesel thing......

To quote Richard Thiel -- Keep Your Marine Diesel Running .... "You cannot determine how clean or dirty your oil is by looking at it, because today's high detergent oils are designed to turn black almost immediately after use. The only way to really determine the condition of your oil is to draw a sample of it and send it out for an analysis."
If black color is the only issue you are observing, ignore it. Run the oil until the manufacturer recomennds changing it despite its color.

 

[Ron20324]

At a recent Yanmar seminar the guy had a demo valve head. Your question was raised about oil, and he showed us the number of places oil could pool up and not drain back into the pan. And he said, yes, though warming the engine/oil up before changing it does make it easier to pump out, it also leaves that dirty oil all through the engine. I just pumped my oil out cold and was not a problem. Change the filter, too. The oil can turn black almost as soon as you start the engine, but that does not mean it is not good.

 

[larryw]

The oil in my Perkins stays amber for a long time, almost til change time, but some engines turn the oil black right away. Ron is right, run til change time.

 

[Steve Dion]

Michael:

This is common with the older engines. Our 2GM was also like this. Our 3JH will have cleaner oil after 30-40 hrs.

 

[heart of gold]

Very typical of any diesel, marine or otherwise. Don't be alarmed, its normal.

 

[Ross]

I found that if I suck all of the oil from the crankcase and then turn the engine by hand several turns to empty the oil filter and suck out the rest of the oil. The oil doesn't turn black quite as soon. but diesel enignes make a lot of carbon and that is what makes the oil black.

 

[mcaswell]

Thanks all... appreciate the replies!

--Michael

 

[rpwillia]

More info

... warming the engine/oil up before changing it does make it easier to pump out, it also leaves that dirty oil all through the engine.

Ron, This sounds a bit heretica, as I was always taught to change oil (car, boat, etc) when it was warm so you would get all of the crap that is supposedly stirred up and suspended in the oil. Interesting the rep stated that, were there any facts he brought in to support that:naughty:? Now saying all that, it is based on "friends" telling me that, so the factory rep would be a bit more credible.:dance:

 

[seadaddler]

Black

My new 2007 with 3GMY when changing the oil always turns black,problem we are pumping the crankcase with a tube stuck down in the bottom of the pan and it does not all drain like in car or truck that drains out the bottom of the pan.
Just change it and the filter as needed and you will be good to go,some people install a drain plug to drain it better which is a good idea but I have seen a lot of bolts come loose on my 2007 yanmar from the engine I guess vibrating and would not want to worry about the drain plug ever coming loose.
I know of a catalina owner that happen to and destroyed the engine.
Nick

 

[Ron20324]

Ron, This sounds a bit heretica, as I was always taught to change oil (car, boat, etc) when it was warm so you would get all of the crap that is supposedly stirred up and suspended in the oil. Interesting the rep stated that, were there any facts he brought in to support that:naughty:? Now saying all that, it is based on "friends" telling me that, so the factory rep would be a bit more credible.:dance:

Well, if you run the engine first, then all that crap is now throughout the engine and probably will not totally drain down to be pumped out. As stated, there are a number of places the oil can pool and never drain back down, but will mix in when the engines runs. When I pumped out the oil the other day, I waited a while and pumped again and got a little bit more out.That's why some folks will change oil using cheap-o stuff, run the engine, then drain and put in good stuff.

It's a lose-lose situation: Run and spread the oil throughout the engine, or drain and leave what is on the very bottom of the pan. I plan to change it before a DelMarVa trip in a couple months anyway.

 

[Ray Bowles]

Cranking oil out of engines.

To crank over an engine to help remove more old oil when changing the oil is best left undone.
When an engine is first started up it runs for a few seconds with the only bearing protection provided by the film of oil left in it from the last oil pumped prior to shutdown. If you start the engine with a dry oil filter, and after having tried to empty the system, then it takes longer for oil to fill these voids and come up to pressure. In a diesel, and to a lesser extent in gas engines, this is the time of greatest damage. After the oil change if you can prefill the oil filter with any amount of oil ,up to completely full, then the period of no oil pressure is greatly decreased.
Cranking an engine dry of old oil also empties the oil pump which compounds this problem.
With all our high performance and racing engines we mount pressurizing systems to build oil pressure before cranking or starting the engine.
Is this a major problem for diesel engines? No, but it doesn't help at all and is best avioded.
Ray