Help Please - Increased Oil Consumption

[Darby695]

First Post, I'll try to put symptoms as accurately as possible.
I've owned this Cat with Volvo DI-30's for 4 years Port Engine Perfect, Stbd Engine always used some oil 200 mils over 4-5 hours.
Decided to refresh the engines before Cruising Season.
Replaced everything as usual, fuel/ oil filters, impellers .
The troublesome engine overheated once prior to the service (shut down immediately) ,so changed all raw water pipes, flushed the heat exchangers, replaced both mixing elbows.
HOWEVER ON THE TRIP TO THE HAUL-OUT 6 hours running used 1.4 LITRES ON STBD ENGINE.
PLEASE HOW DO I TROUBLESHOOT THIS.
( For info, both mixing elbows were 80-85 % blocked - Stbd elbow had a Black Greasy buildup near the header about 1/4 inch )
I tried something different with the Stbd elbow by having a light Ceramic Coat so as to compare service life etc, water flow is the same both sides.
Engines 10 years old Port 2440 hrs. Stbd 2240

Thanks in Advance

Darby695

[Lepke]

Sounds like stbd engine burns oil. Compression test or better yet, a leak down test will give some indication where the problem lies. Oil can get into the cylinder thru bad rings or valve guide. Could be just one valve of one cylinder or one broken ring. The greasy build up just confirms what you already know. No oil in the water or no water in the oil should rule out a head gasket.

[DougR]

Its a bit hard to follow your sequence of events, but it sounds like the stb. engine always burned a bit of oil, then you had an overheat on that engine, then it began to burn way more oil......

Perhaps the overheat caused a slight piston scuff/seizure on that engine and that has bound up the piston rings on one of the pistons. This will cause the loss of oil control, allowing oil to make its way up past the piston and into the combustion chamber. It frequently also allows compression to push down past the piston and over pressurize the crankcase. This pushes oil vapor out the crankcase breather and into the inlet manifold where it gets pulled into the cylinders, again resulting in more oil burning. Open the oil fill cap when the engine is idling and see if there is excessive crankcase pressure. If it's woofing out the oil fill port it's a good bet you have a scuffed piston.

The leak down checks as listed by Lepke will help point to a suspect cylinder, but if it's a scuffed piston, you can usually tell which one by looking at the cylinder walls after removing the cylinder head.

DougR

[Darby695]

Thanks Guys,

Eventually I was at my wits end, searched all of Australia for best prices for new engines / short engines etc
Whilst cruising north to the Whitsundays my son suggested a fuel and or oil additive to possibly free up a possible stuck ring or rings. After an extended web search and some phone calls to mining company's suppliers we agreed on a relatively cheap "SNAKE OIL" treatment. We we figured $210 for the fuel and oil treatments was minor compared to the rebuilding or replacement costs of the engine.
So after 2 oil clean out flushes and 2 new filters and adding a fuel treatment there has been a giant improvement. After 20 hours running the results are as follows.

Smoking not visible and oil consumption reduced to less than 40 mls per hour. My intention is to very closely monitor this consumption by having "scribed" between the top and bottom marks 10 segments and the measure how many milliliters per hour being burnt/ lost. (We only fill up to the 80% mark as consumption above the 80% mark appears higher.
Thanks again this is a great learning site!

[Wotname]

^^ good news and please keep us informed about the longer outcome of the "fix".

Not often that any miracle cures work but this might be the exception.

[a64pilot]

If that worked, and it apparently did, then a previous owner didn't change oil nearly as often as they should.
I would run a very good oil and filter, and be sure to change the filter often as there is apparently a lot of sludge in that engine, the filter of course catches that and you don't want it clogged.
As an aviation mechanic forever, a lot of people swear by Marvel Mystery Oil. I thought it pure snake oil myself until I saw it keep R-1340 aircraft radial engines from sticking valves and I finally became a convert.
Old school was one quart of automatic transmission fluid per oil change, ATF has a very high level of detergent and really will help clean things out, but I believe the Mystery oil to be better.

[Wotname]

Originally Posted by a64pilot

If that worked, and it apparently did, then a previous owner didn't change oil nearly as often as they should.
I would run a very good oil and filter, and be sure to change the filter often as there is apparently a lot of sludge in that engine, the filter of course catches that and you don't want it clogged.
As an aviation mechanic forever, a lot of people swear by Marvel Mystery Oil. I thought it pure snake oil myself until I saw it keep R-1340 aircraft radial engines from sticking valves and I finally became a convert.
Old school was one quart of automatic transmission fluid per oil change, ATF has a very high level of detergent and really will help clean things out, but I believe the Mystery oil to be better.

Good advice although I have never been willing to use ATF myself!

And as for Marvel Mystery Oil, I have never seen an old school GA hangar without a can of it somewhere...

EDIT: According to the Wkipedia entry, the composition of MMO is straightforward and thus one should be able to make it at home
https://en.wikipedia.org/wiki/Marvel_Mystery_Oil

[Diesel Bill]

You guys pretty much nailed the diagnosis on the oil burning, so not much for me to add.
One thing I will add is any restriction in the air filter or inlet tract can pull oil past the rings.