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Old 03-06-2013, 17:32   #1
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Volvo MD2B : lost compression in 1 cylinder

My MD2B was hard to start and I noticed a wisp of white smoke coming from in between the cylinders. I managed to get it starting but then it started overheating probably from running on a single cylinder. When cranking the engine with just the forward compression lever down I can hear the gas hissing out of the forward cylinder and making some white smoke come out from somewhere between the two cylinder covers. With just the aft lever down the aft cylinder compresses and ignites.

Is this a gasket or a valve issue ?

Would I be able to fix this myself ? I've got quite a bit of room over the engine to work on it.

thanks

-tavis
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Old 03-06-2013, 17:48   #2
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Re: Volvo MD2B : lost compression in 1 cylinder

Well its at least a gasket issue but sounds like you have cylinder pressure escaping past 2 gasket surfces. Did you smell/ taste the white smoke? The high temp is cylinder pressure getting into the cooling system, probably. Sounds like you have a really bad head gasket.
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Old 03-06-2013, 17:56   #3
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Re: Volvo MD2B : lost compression in 1 cylinder

Over heating is caused by combustion gasses getting into the water jacket. It probably is a blown head gasket. You never know for sure until you get the head off. It could be a cracked head but unlikely since you can see where it is coming from. The white smoke is probably steam. The crankcase will have coolant in it. Be sure to get that drained out and flushed.
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Old 05-06-2013, 10:54   #4
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Re: Volvo MD2B : lost compression in 1 cylinder

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Originally Posted by westwinds View Post
Over heating is caused by combustion gasses getting into the water jacket. It probably is a blown head gasket. You never know for sure until you get the head off. It could be a cracked head but unlikely since you can see where it is coming from. The white smoke is probably steam. The crankcase will have coolant in it. Be sure to get that drained out and flushed.
evidence of water in the crankcase will be water mixed with oil on the dipstick ?
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Old 05-06-2013, 11:05   #5
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Re: Volvo MD2B : lost compression in 1 cylinder

Yeah, it should look milky white emulsified water/oil.
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Old 05-06-2013, 13:28   #6
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Re: Volvo MD2B : lost compression in 1 cylinder

The best way is to just drain the oil. With a blown head gasket or crack in the head, there WILL BE coolant in the oil. Antifreeze in the coolant, which will be present in the combusiton chamber and subject to combusiton temperatures and pressures will form highly acidic compounds that attack bearings. Drain the oil.
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Old 05-06-2013, 19:23   #7
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Re: Volvo MD2B : lost compression in 1 cylinder

M2B's are getting long n the tooth and hard to find parts for. I had one om my Wauquiez 33 and it died a slow death. I couldn't justify putting more money into it so I am in process of repowering with a Beta 38 hp. It is a reasonably easy drop in.
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Old 05-06-2013, 19:42   #8
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Re: Volvo MD2B : lost compression in 1 cylinder

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M2B's are getting long n the tooth and hard to find parts for. I had one om my Wauquiez 33 and it died a slow death. I couldn't justify putting more money into it so I am in process of repowering with a Beta 38 hp. It is a reasonably easy drop in.
If the M2B has no heat exchanger, that is an engine directly cooled with salt water, it should have died a while back from corrosion of engine and head. Parts are very expensive and some impossible to find so maybe a new engine or something used on ebay. The M2B is a 25 horsepower engine, rather slow turning and heavy.
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Old 07-06-2013, 14:44   #9
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Re: Volvo MD2B : lost compression in 1 cylinder

I'm not going to put a new engine in because I'd like to sell this boat soon. So i've decided to take it apart and replace the gaskets myself. I've just managed to get the exhaust manifold off and I have some photos. Any opinions on how they look ?
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Old 07-06-2013, 14:51   #10
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Re: Volvo MD2B : lost compression in 1 cylinder

Did you decide it was not a cracked head and just a leaking gasket?
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Old 07-06-2013, 17:19   #11
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Re: Volvo MD2B : lost compression in 1 cylinder

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Did you decide it was not a cracked head and just a leaking gasket?

There is no water in the oil but still no compression in cylinder #1 when starting. Cylinder #1 does seem to start firing once the rpm get going via second cylinder firing (ie. I can get the engine started with just cylinder #2 firing).
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Old 07-06-2013, 17:55   #12
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Re: Volvo MD2B : lost compression in 1 cylinder

Guess I never understood why people said there would be water in the oil. You can't get there from there unless you have no piston rings.. You will be wasting a lot of time and effort and money if you don't know if it has a cracked head. It's not expensive to get it checked at any automotive machine shop. If however you see obvious damage to the head gasket then maybe you could rule out a crack but the head might be warped so you should get it re-surfaced, also cheap and something easy to check.
You seem to be doing great, keep up the good work.
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Old 08-06-2013, 21:14   #13
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Re: Volvo MD2B : lost compression in 1 cylinder

There are gaps on each piston ring where they come around to form an almost complete ring, but there is a gap to let the rings flex. For some reason, water does get by the rings. I have seen it happen many times, water in the oil, crack in the head , blown head gasket, or even a crack down the cylinder wall. If there are wet sleeves, then a failure of the seals around the sleeves can fail, like on a Detroit two cycle where there is no coolant, the engine gets hot and destroys the seals.
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Old 11-06-2013, 21:06   #14
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Re: Volvo MD2B : lost compression in 1 cylinder

Now I can't seem to get the head off because there is a oil pipe blocking it. It seems the only way to get the oil pipe off is by a nut that is all the way down inside of the cylinder block where it connects to the oil pump ? How am I supposed to remove the head without taking out the oil supply pipe ?

The part is #17 on this schematic : Volvo Penta Exploded view / schematic Lubricating System: A MD2B - MarinePartsEurope.com
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Old 11-06-2013, 21:11   #15
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Re: Volvo MD2B : lost compression in 1 cylinder

Ha! Looks like you need to take off the other cylinder head. Bummer dude.
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