Volvo sx-a: charcoal colored substance in exhaust water

travelon1979

Cadet
Joined
Jun 14, 2010
Messages
15
While winterizing my boat in October I noticed the exhaust water flowing off my concrete driveway and into the grass had charcoal colored substance. It wasn't oil, lube, or fuel as it did not have a rainbow sheen. When I moved my finger through it reacted almost like it was a solid but didn't appear to be metallic. It was more like a film.

If it's not lube, oil, or fuel what could it be?

Based on research could it be carbon from running rich during warm up? I've never noticed the substance before so is a bit concerning as I'm sure I would have noticed so why would it be running rich enough to flow out carbon

I send my oil off to be analyzed. My analysis last year came back as having more than the recommended amount of fuel in the oil. Over 4% for a marine engine was the labs cutoff. They stated they allow more for marine engines. I warmed the engine for about 5-10 minutes so assumed that would burn off the excess fuel before taking the sample. I was told by several people not to worry. But now that I'm seeing what could be carbon I'm concerned I may have a fuel injection issue.

Any advice or knowledge anyone would like to bestow on me before I drop off to the dealer.

Thanks again!
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Marine engines do generally run richer than auto/truck engines, especially at low speeds. You are probably just seeing soot. As for the excess unburnt Hydrocarbons in the oil, warming the engine by idling for 5 - 10 minutes is what puts the unburnt fuel and water(a byproduct of combustion)into the oil. To burn it and more importantly boil the water out of the oil will require a much longer running period at higher rpms to get the oil hot enough to vapourize the fuel and water
 

travelon1979

Cadet
Joined
Jun 14, 2010
Messages
15
That's what I figured and my service center agrees after a quick diagnostic. Thank you for the feedbac!
 

Lou C

Supreme Mariner
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Nov 10, 2002
Messages
11,798
Agree with the above, also make sure your thermostat is not stuck open, this will cause extended warm up times and more fuel dilution of the oil. The Volvos usually have a 160 'stat and should run between 160--->175*. If it never gets over 120* then your stat is not closing all the way....

The only other thing I can think of, is a leaky power steering cooler that might be leaking p/s fluid in to the exhaust water, is your p/s fluid low? Might want to check. Also if there is an engine oil cooler, that is water cooled same thing, what does you motor oil look like? Any milkiness? Take off the oil fill cap with a cold engine and see if there is anything looking like mayonnaise in there.
 

travelon1979

Cadet
Joined
Jun 14, 2010
Messages
15
Agree with the above, also make sure your thermostat is not stuck open, this will cause extended warm up times and more fuel dilution of the oil. The Volvos usually have a 160 'stat and should run between 160--->175*. If it never gets over 120* then your stat is not closing all the way....

The only other thing I can think of, is a leaky power steering cooler that might be leaking p/s fluid in to the exhaust water, is your p/s fluid low? Might want to check. Also if there is an engine oil cooler, that is water cooled same thing, what does you motor oil look like? Any milkiness? Take off the oil fill cap with a cold engine and see if there is anything looking like mayonnaise in there.

​- I'll definitely check the PS fluid.
​- Engine oil was spotless. I send that off to have labtested after each season and it was perfect and exceeded all thresholds (Amsoil). Nothing foreign in the oil.
​- My last trip out on the boat the temp was normal after cruising. I'll definitely keep an eye on this on my first trip out this year..hopefully days away. :)

​Service center believes it was carbon as well but I'll check the above just to be sure.

Thank You
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,798
Is this an EFI engine or a carb? If a carb engine, make sure the choke valve opens all the way once the temp gauge gets up to 160*. Usually you don't have too rich running problems with EFI, its common with carbs because the choke shaft needs to be cleaned each season...but if a fuel injector leaks, or the cold start enrichment valve stays on too long, it is possible.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
That is totally normal. As the engine warms up the soot from when the engine started up cold will take a little while to work it's way out.
 

mikeneal

Senior Chief Petty Officer
Joined
Jan 28, 2004
Messages
710
I had noticed same and have sent several oil samples in and they always have a low level of fuel in them. (Carb motor)
 
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