Water in genset oil - how to clean it out?

Hi everybody from Brisbane,

My Onan genset got saltwater in the oil (pinhole leak in the exhaust riser), the oil went milky. Luckily we caught it immediately and have replaced the riser and exhaust manifold.

The milky oil has been drained.

Here is my question - what is best practice to get rid of all the milky oil residue and ensure the gen runs on completely non-contaminated oil? Do we just change the oil/oil filter several times, with a brief crank between each change?? Is there a better way to deal with it???

Thanks very much for your replies!

Hamish.

Hi,


Here the general way to wash the machine inside is to add diesel fuel to the oil set from 10 to 15% by volume, use the engine without load for 10-15 minutes and shut down. You continue like normal oil change and new filter also.

P.S. This solution was also with WV cars when they made a major emission droid for their diesel car.

NBs

Don't wait. Do an oil/filter change and run for 3 minutes or so. Repeat a few times, increasing run time a minute or two each time until all milky oil gone. Adding diesel draws a bit of debate, Ski will weigh in I'm sure. But again do flushes ASAP.

Same thing happen to me on my main earlier this year, did 4 oil changes before being able to get rid of the sludge. Ran the engine 5 minutes after 2 first oil changes, a bit longer after the third (30 min), and same after the fourth. Changed oil filter each time.
Note: my engine is an old beast so may not be the same with more modern engines.

L

"Same thing happen to me on my main earlier this year, did 4 oil changes before being able to get rid of the sludge."


This night be a notice for those that anchor out on the quantity of oil and filters that should be onboard at all times.

FF said:

"Same thing happen to me on my main earlier this year, did 4 oil changes before being able to get rid of the sludge."


This night be a notice for those that anchor out on the quantity of oil and filters that should be onboard at all times.

Click to expand...

Better yet, as exemplified in the OPs case, change those pesky genset exhaust elbows out before they fail. I prefer the 5 to 6 year interval.

sunchaser said:

Don't wait. Do an oil/filter change and run for 3 minutes or so. Repeat a few times, increasing run time a minute or two each time until all milky oil gone. Adding diesel draws a bit of debate, Ski will weigh in I'm sure. But again do flushes ASAP.

Click to expand...

Hi,

Commercial motor flushing treatment contain kerosene carbon compounds C11-C14 often over 50-100% in addition to lighter soluble distillates and aromatics.

The diesel fuel combination is heavier C15-C19 and casoline is the lightest carbon compound C5-C8.

This means I think that about the same thing as the kerosene has been bottled more finely like STP and the added price well.

Diesel as a slightly heavier distillate is not as effective as a kerosene, but works well as a washing agent.

STP motor flusch safety data sheat link.

https://www.workshopwarehouse.co.uk/downloads/dl/file/id/470/vc151.pdf

NBs

If you add diesel to your crankcase and the engine is not new, prepare for a possible runaway...

After a few oil/filter changes, pull the valve cover and check for accumulated sludge on the rockers. If those are clean you are done, if not, keep flushing, maybe using the lighter flushing solutions mentioned above.
My recent engine failure was due to water in the oil. 8 oil/filter changes later, the mechanic suggested the battle had been won and I put the engine back into service, where it failed catastrophically within 4 hours of use. Pulling off the valve covers showed that the battle had not been won, not even close, as the rockers were buttered with grey sludge. Other, sensitive parts not as visible as the rockers had seized by that time.
Good luck with your genset.

Before the first filter change I would pull the rocker cover and use some cutting agent right from the git go.

Let drain well, and then a complete change.

If you have sludged up rockers, try a shop vac first to clean off as much as possible.

What model Onan?

Basically change the oil, run a while, and change again until oil on stick is no longer milky. Then you need to run it under a good hard load and monitor blowby flow (not possible on all models) until no steam is coming out. May take a couple hours. Space heaters and hair dryers are a nice way to get some good load, plus one ac on heat and the other on cool. Want to get the engine hot.

Some models the oil drain is from the side of the pan, if liquid water (not emulsion) is present, the pain drain might not get it all. Some you can use a tube through dipstick hole to hit bottom of pan and get a more complete drain there.

No need for additives, normal motor oil has emulsifying agents and that is enough to scavenge water.

Second that about pulling rocker cover. That tends to be where the emulsion accumulates. If no milkiness up there, you are good to go.

Change oil one last time.