6CTA 8.3 M1 oil in coolant

[alex1]

Hi Tony and everyone else,

I was in my engine room all day today, entire saloon floor taken up for plenty of headspace and light. Was swapping out some old gear oil cooler hoses as well as some coolant vent lines on port engine, after going to the hydraulics shop yesterday. Late in the afternoon, almost everything done I changed my coolant filters. Port engine, no problem. Stb engine… after unscrewing the filter a few turns, the first liquid to come out was black! I get the whole filter off and it’s full of black, oily water and sludge, rather than the nice, runny, translucent blue it should be.

My overflow bottles are old and in poorly lit locations, but it was only at that moment that I noticed the stb bottle was full of black liquid, while the port side bottle was clearly filled with blue liquid.

The oil in the engine appears uncontaminated, and there are no outside leaks or residues in the bilge.

Recently, I’ve been using the boat plenty, and despite some exhaust issues (which are now fixed), it’s been running fine. Last time out was only just a couple of days ago, and there was nothing out of the ordinary – nothing, temps, coolant use, oil, I honestly do check it all, before, during and after each run out.

So, honestly – I can’t even say for sure how long this has been going on.

I suspect it’s an exhaust related issue – so often fixing one thing leads to breaking something else down the line. Could it somehow be related to high back pressure? The new section of dry exhaust that was fabricated for me was 3.5″ID, 8″ pipe to 90 degree elbow to flange (which would mate to mixing elbow). A copy of what was originally there, but had corroded away where the elbow met the flange, with one possibly significant difference – the new flange was fabricated at the shop, because the correct size couldn’t be easily sourced, and its internal hole diameter was actually less than 3″. I realised this would cause back pressure to increase, but wasn’t really sure of it’s effects, so we went ahead and installed it, and it’s been fine, for about 10-15 engine hrs since then. Until now.

Otherwise, if not exhaust related…

Do oil coolers fail on these engines? Mine is a very early model.

Could it be the head gasket, even though there are no other symptoms?

What are the areas I need to check?

Do I dare try to fire up the stb engine, knowing that it is leaking oil into the coolant?

Should I drain the coolant and / or the oil straight away?

Many thanks in advance

Alex

1 user thanked author for this post.

Ron Kasel

Topic

[alex1]

Done about 25+ hours now, since the flush, including some longer run outs, where engine engine speeds have been 1800-1900 Rpm. Now – we have dirt in the coolant. It’s not a lot, but quite clear to see. Any thoughts? Engine has still been operating at expected temps and nothing else out of the ordinary going on.

[Rob Schepis]

Progress is good!
If that recovery bottle is really bothering you and you want to replace it:
https://www.sbmar.com/product/cummins-marine-coolant-overflow-bottle/

[alex1]

Hi all,

Just wanted to update you…

Managed to complete the first stage of flushing out the engine. Took about 4 hours. I started with the filter off line, then put it online for the last 1.5 hours, till I finally managed to get clean water coming out. Ended up bleaching the overfill bottle as could not get the dirt off with a brush no matter how hard I tried, and it is still slightly stained inside, new cap on expansion tank, filled with 3:1 water/coolant with filter back off line.

3 pics attached, showing state of coolant after 3 hrs (1st pic) and 8 hours (2nd & 3rd pics). You’ll notice the striking clarity! Haven’t had any really long run outs yet, so I’ve been taking it relatively easy. I’ll start pushing her a little more next couple of trips to see if that changes things, and let you know how it goes. Stay tuned…

[Rob Schepis]

1,000 rpm at the dock “alone” — you are a brave man!
That gasket is a home made gasket from a thick sheet of cellulose fiber gasket material…

[alex1]

Now pics of the exhaust as well…

When showing the above pics the local, very experienced and well respected mechanic – he said it was exhaust gases going into the coolant somehow. That was even before I mentioned that that engine’s exhaust (the dry part) had recently been redone. Also attached, are pics of the exhaust manifold / turbo gasket, showing a 3mm thick hard gasket material has been used, which looks a little like it’s actually made from wood! The last pic is of the port engine gasket (for comparison) – which looks a lot more like it should do, i.e. barely 1mm thick and not at all wood like. So, at this point, the prime suspect is the thick woody gasket. New parts already picked up from local Cummins centre, as well as 40L of new coolant, in preparation. Yes, I have also studied the Tony’s Tip regarding gasket replacement, and already have all the necessary gunk, etc. But of course, before I get carried away, I needed to follow Tony’s suggestions as above.

So, Friday started with draining the coolant, closing of the valves to the filter, filling with water to half the tank level, then taking the boat over to the pontoon to tie it up. Did as told, put engine in gear at 1000 rpm while tied to dock, and started slowly draining (and re-filling) water to flush engine. As I was on my own, this was not a fun task, as every time I left the helm and went below to drain and fill, I was worried about the boat breaking free and flying away from the dock. Eventually, after about 30 minutes of draining and filling like this, I noticed no discernible difference in the color of the coolant (it was all coming out dirty and black), so left it in neutral and carried on for another 2 hours, which also saw no change in the coolant coming out the drain, still dirty and black. I was booked to take the boat out on Saturday, so at this point I decided this job would have to carry on into next week. Drained the engine and filled with 20/80 coolant/water mix and put filter back online.

Took her out on Saturday, and just pottered around at 1,200 rpm max. That STB engine has always heated up faster than the port engine, but both engines were settling at the same, usual temps, although I was taking it very easy. Everything else seemed fine. Got back late on Sat, so did my usual shut down routine (again everything looked OK, inc. coolant levels in expansion bottles) and went home to watch the World Cup. I’m going back to the boat tomorrow to find an assistant and try to flush the engine again. I will let you know how it goes.

[alex1]

Pics of STB engine

[alex1]

OK, first of all – thanks very much for all the replies – honestly, I appreciate it so much.

Now, despite my chosen title for this thread, I am relieved to announce that there is no oil in my coolant, nor is there coolant in my oil (although i’m still gonna try to get a sample tested soon). When I took off the coolant filter it did appear as black oil dribbled down the side of it, but i guess there was just some diesel residue on the filter o ring that deceived me.

Carrying on, the coolant his discolored, as you can see from the first photos, showing (from left to right) STB engine coolant from top of tank, STB engine coolant from coolant drain, Port engine coolant (for comparison – which is as clean as it was when fresh from the bottle).

Clearly the filter is doing its job, as it was jammed with black sludge and heavily discolored fluid – see third picture. Forth and fifth pic show oil is not (obviously) contaminated.

Turns out my overflow bottles are just old and worn on the outsides, so hard to see through. For example, when filled with plain water, you can barely see the level in the bottle. In actual fact, the coolant in there was not black, it was the same forest green as in most the rest of the engine. So, that’s where I was last Friday, after making the initial discovery (and spoiling my pants) late on Thursday. Next up, I’ll post pics of the engine…

[Tony Athens]

Cummins 6CTA 8.3 250C issues

I want to start out like this………..Engine hours wise, your engine is “as new”..This is a 20000-50,000 hour engine between rebuilds when run and maintained properly. As to internal engine wear based on engine use , it is not even well matured yet………….

AS to all the rest, your issues, although I do know exactly where they are ( or even if you have any) are from a total lack of proper maintenance sitting at the dock over the last 20++ years…. Ever heard the term “Marine Age”, and in your case, maybe just “age period” and the total lack of dealing with “time”….

If you really want to sort this out, it has to be done in steps & like this as a “practical hands-on matter” ………….

1) Drain every drop of coolant . Shut off the coolant filter valves an leave them shut for now) Fill the engine up with straight water, but leave the tank at about 50% full..

2) Run the engine at the dock at about 1000 RPM in gear ( tie the vessel off real good so it is 100% safe).. watch the temp closely and the coolant level ( tank at about 50 % full, and when the temp gets up to 185-195F ish, start draining coolant under the oil cooler ( there is a pet cock there that you can control) and while it is drains, add new water slowly to maintain the 180-195 temp..

3) Do this as long as needed to flush the system until all the “black water” is gone..This could easily take 2-4 hours to really flush it out.. Remember, what you have in there could easily be 10-20 yrs old.

4) Wash out the plastic expansion tank so it is “as new inside”.

5) Then fill, with about 20-30% coolant / 70%-80% water……..Fill the overflow bottle up about 50 %..

6) Buy a NEW fill cap for the main tank

7) Go fishing or what ever you do–Put on at least 10-50 hours, and report back..

Tony

[alex1]

Info from Dataplate:
Model: C8.3M1 (250) / 6C8.3
ESN: 45370773
CPL: 1221

Boat is a 46′ Taiwanese cruiser by Gold Island. Boat and engines are from 1996. I have had the boat 3 years, during which time I have put on about 150 engine hrs, although boat usage has been much more regular lately, compared to earlier ownership. Engine hour readings on tach are not reliable, but lets assume it’s around 2000, i.e. pleasure boat usage, not commercial. Used in saltwater in Hong Kong. I typically run the boat about at low speed, under 10 knots, at 1400 – 1800 RPM (1400 gives about 8 knots, 1800 gives about 10 knots). I almost never go up to or over 2000 RPM. Boat goes out about twice a week at the moment, adding 2-4 engine hours each trip.

Engines are serviced by myself. Last oil (engine and trans) change was in April, and its been every 6 months prior to that. About 8 months ago I totally cleaned each engine using Fleetguard’s Restore product, following the instructions carefully, inc. flushing with plain water, etc., before filling up with ES Complete pre-mix. At same time, I swapped out most of the engine hoses (many bought from SBM), and of course, changed the coolant filters. About 18 months ago, I changed the thru hulls, sea cocks, sea strainers, cutlass bearings and even the prop shafts. Beyond that, no major works done to engines in my 3 years of ownership, except for the recent exhaust riser replacement – hence my suspicion that it is an exhaust issue.

As noted in opening comment, no obvious signs of water in oil, although have not sent oil off for analysis (yet). Gear cooler is indeed salt water cooled, so can’t be gear oil.

The new exhaust will definitely produce more back pressure than before, because of the reduced hole in the flange mating to the mixer elbow. Turbo outlet to exhaust bolts are all badly corroded, so rather than try to take off entire exhaust riser, we decided to keep the first 90 degree elbow and grind our way through the exhaust pipe after that, welding on the new exhaust to the old elbow. When grinding off the old exhaust pipe, some material could have fallen down into the turbo, although there has been no noise or other sign of trouble from the turbo since doing the exhaust, in fact – the engine seems to be running fine, and there are no visible leaks or cracks anywhere, nor drips in the bilge.

I’m heading back to the boat today for further investigation, and i’ll take some pics of the engine and post them later.

[Philip]

Can we get an exact engine model/serial and cpl number. Also what’s the history of the engine, hours, salt/fresh, repairs and regular max items done etc.

Lots of areas it could be… is there any sign of coolant or water in the oil? Any milkiness color to the oil? Could be the engine oil cooler. The gear coolers are usually salt cooled. Manifold crack could give you exhaust into coolant which appears as black. Head gasket and or cracked block would be last on the list.

And how about some picture of the engine from all sides and the top.

If it’s oil or exhaust either can reduce your cooling capacity so limit your run time to diagnosis until you get it figured out.

Phil

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