Volvo Penta MD22 - smell of burnt rubber at high revs

Discussion in 'Diesel Engines' started by SALLY, Mar 29, 2011.

  1. michael pierzga
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    michael pierzga Senior Member


    Every engineer has a pyrometer. Also guys who sell propellors use pyrometers to judge prop load. It would be inserted into the exhaust upstream of the water injection to judge engine condition.

    Is the water injection jacket cool ? around its full circumference ?


    Hmm...I cant think of anything inside an engine that would give off a burnt rubber smell.

    If your exhaust system is newly fitted its possible that joint compound like copper paste used to bed the fasteners on the exhaust flanges is burning . Normally you smell that inside the engine room also.

    The air intake system.. filter... is correct....pieces arent coming free and combusting ?

    Hmmm................... rubber burning smell normally means heat....a hot component.
     
  2. SALLY
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    SALLY Junior Member

    Thanks Michael, but what do you mean by 'water injection jacket'? The elbow behind the heat exchanger? That is warm, but not hot. I did only feel at the top though. Next time I'll check the bottom too.

    The exhaust system has not been changed, just the elbow and the inner parts of the heat exchanger. And as I said, no smell in the engine room at all. Only outside.

    I'm going to the boat tomorrow and do some extra checks. I'll keep you posted.
    Thanks!
     
  3. michael pierzga
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    michael pierzga Senior Member

    The water injection point .....were water is added to the exhaust before discharge. I dont know the Volvo style. Some are literally water jackets and the sea water is sprayed into the exhaust thru perhaps a dozen holes around the circumference of the exhaust. Its common on big diesels. If several holes are plugged, part of the exhaust get very hot .

    From the look of the simple engine description I have for your motor I think you have a normal single injection point.

    Besides..if you can put your hand on it, obviously the complete cooling system is working.

    And ...no smell at normal cruise revs..but burning rubber at full speed...under max load. . Hmmm.....mysterious.

    Can you give her full speed, in gear, while tied to your dock ?
     
  4. SALLY
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    SALLY Junior Member

    OK, I understand now which part you mean. Volvo call it 'the elbow', and it's a part that I renewed a few months ago. It has several injection ports for raw water. No smell at all at normal cruising speed.

    I can drive the boat at full throttle when moored in the dock, but strangely enough, the smell of burnt rubber is then not as bad as when I use the same revs when cruising in open water. Getting even more mysterious, isn't it?
     
  5. Frosty

    Frosty Previous Member

    No not at all but clarifies it a little, At mooring you are not getting full power but full RPM, the heat generated is much less when not loaded.

    This again points to insufficient cooling.

    You seem to have changed every thing.
     
  6. SALLY
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    SALLY Junior Member

    When I refferred to 'testing moored in the dock', I meant loaded: gear engaged, prop turning. So I think that's quite close to actual driving the boat, except for the water flow under the raw water intake. Could that make a difference?
     
  7. Frosty

    Frosty Previous Member

    Water can "skip" the inlet on faster boats needing a very fine scoop if your exceeding 20 Kts you should check that. If you have a scoop strainer it could well be that if we are assuming that insufficient water is the problem.

    Its not really the same, at the dock, in gear your unlikely to reach full RPM as you would if at sea.
     
  8. SALLY
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    SALLY Junior Member

    Maximum speed of my 10-tons motorsailer is about 8 knots. But I understand your point about the difference in the dock. And I do have a scoop strainer, but then again: I see a very powerful jet of exhaust water exiting the exhaust. It doesn't seem less than before, when there was no smell of burnt rubber.

    Of course, this is all based on visual observation, not measured.

    Someone suggested a change in diesel quality. I must admit that since I have the smell, the diesel looks different (more yellowish). Probably they add some biodiesel. But could this account for a smell of burnt rubber? Or could it be that this mixed diesel has a higher exhaust temperature as a consequence?
     
  9. Frosty

    Frosty Previous Member

    If your sure its cooling and no damage is occurring then we are curing a problem that isn't there.

    Are your drive belts in good condition,alternator , water pump etc, could be that your new impelor is loading the drive belt or you have a load on the alternator.-
     
  10. SALLY
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    SALLY Junior Member

    The cooling looks perfect and I have not noticed any damage since I smell the burnt rubber, but I don't feel comfortable smelling anything burnt on my boat; it means somewhere something is heating up and that worries me.

    It's not inside the engine room, because the smell is not there at all; I only smell it at the external exhaust.
     
  11. kenJ
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    kenJ Senior Member

    I have read that biodiesel gives off a "popcorn" type smell. It could well be that something added to the fuel causing it.
     
  12. SALLY
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    SALLY Junior Member

    Well, I've been to the boat today and did a few more checks. I let the engine run warm to normal operating temperature (85° C). Then revved it up to 3000 rpm for a few minutes so I got the smoke and the smell.

    A few remarks:

    - My wife, who sees colours better than I do, says it bluish grey smoke.
    - the exhaust water (outside the boat ) is very cool and abundant
    - the elbow stays cool to the touch, approx. 25°C
    - the rubber hose stays cool to the touch, approx. 20°C
    - engine stays at normal operating temperature
    - no leaks anywhere
    - some traces of diesel oil (or oil?) in the dock

    My temporary conclusion: the rubber smell is certainly not the exhaust hose. Everything in the exhaust line is nice and cool. Where is that smell coming form. The mystery stays...

    Would adding some additive to clean the injectors help?
     
  13. kenJ
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    kenJ Senior Member

    Have you asked other boaters in the area if they are smelling anything different? If it is a fuel source/addditive problem it should be occuring to others too.
     
  14. SALLY
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    SALLY Junior Member

    Well, that's exactly what I'm going to do next. Although I doubt it, because last year we toured with two boats and I didn't smell anything form the other guys exhaust - well, his boat's, I mean. But perhaps it's only with Volvo's, he had a self-marinised Toyota engine.
     

  15. anthony goodson
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    anthony goodson Senior Member

    Unless other symptoms develop ,I would just enjoy your boat.
     
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