another MD11c question

[DavidGrieves]

Hi

Ref: Volvo Penta MD11c

I have taken the cylinder blocks off the crankcase. So now I need a couple of geskets for between the bottom of cylinder and crankcase. I phoned up Keyparts, chap there tells me they aren't a gasket they are a spacer and they come in two thickneses, 0.2mm and 0.3mm.

So now to the question, do I need a new one or re-bed the old one on a compound, and other than measuring the old one how do you determine which one is right for my engine?

Thanks

David

 

[scottie]

the cylhead nuts have nylon inserts
the cyl base shims should be metal and reused do not mix them up as they determine the compression ratio

 

[boatmike]

They are in fact spacers as you were told. If for any reason you need to reface the cylinder head,(which is often necessary on these old donkers) you can compensate for the metal removed by fitting thicker spacers. Otherwise just clean everything and re-fit. A light smear of non setting gasket seal like red hermetite is OK but no other gasket is required.

 

[VicS]

Yes that's right there are shims between the crankcase and the cylinders which set the compression. The workshop manual (download from http://www.bluemoment.com/manuals/VolvoMD11C_D_17C_D.pdf if you do not have one) tells you how to determine the thickness required. Alternatively measure the thickness of the old ones after cleaning them up and fit the same again.

Do not use compound.

There are big O ring seals located in the top of the crankcase. It would be advisable to renew those as well.

The parts diagrams at http://www.marinepartsexpress.com/VP_Schematics/ are also useful

Parts 33 are the shims and 38 the O rings on the cylinder block drawing

 

[Bilgediver]

So now to the question, do I need a new one or re-bed the old one on a compound, and other than measuring the old one how do you determine which one is right for my engine?
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These gaskets are spacers and not only are they engine specific but also cylinder specific so if you have messed them up you need to determine the correct thickness before finally assembling the engine.

The thickness of these spacers is adjusted to give the correct cylinder head to piston clearance and the target figure will be found in the workshop manual and possibly around 0.8MM

You will have to assemble the engine with nominal shims in place and measure the clearance between the cylinder head and piston at top dead centre. Compare the figure obtained with the required clearance and then adjust the shims as required.

Not quite as fiddly as it seems and the clearance can be measured with lead wire or solder wire placed on top of the piston which is measured after the test with a micrometer.

 

[kandoma]

I have taken such an engine several times apart. I would recommand strongly to replace the two yellow or orange silicon O-rings near this bottom shims. This O-rings are not ordinary o-rings. They have a very strange form and seal the engine block towards the valve mechanism. They do not look damaged, but most of them, if reused, will leak like a sieve.

Peter

 

[VicS]

I'd forgotten about those. 3 of them it appears and available as a set shown as #35 in This diagram

 

[DavidGrieves]

Thanks very much for the tips and advice. I was going to reuse the O rings but I'll order some new ones in the morning.

Thanks again everbody

Dave

 

[boatmike]

You are right of course. The seals are on the O rings. I had forgotten about those. Must be at least 15 years since I did one!