Smoking' MD2B / piston removal

[phammy]

Originally Posted by a64pilot

Your call. I feel you can’t change oil too often, but it s likely that I have wasted oil in my life too, but oil is cheap.
I’d run it in on new oil myself, and then change that at say 10 hours and then from then on, regular oil change intervals myself.

it's this seasons oil and it's only done about 5 hours so i'll keep that for running in and prepare for an oil change when everything is happy

[phammy]

I have heard that the vent pipe from the filler cap should be routed back into the frying pan air cleaner? Can anyone confirm this because it seems strange to me that I would vent so much smoke back into the air cleaners.

[Shoalbay]

phammmy said:
"• I see in the workshop manual that I simply lift the cylinder blocks upwards
• Then I have to guess (not mentioned in manual) the next step is to unbolt the con rods?
• Then I'm guessing I next re-fit the piston on the bench (using ring compression tool)
• Then bolt the con rod back on via the inspection window????
Otherwise i don't understand how i'd get the piston rings compressed"
Sh0albay says: if I recall correctly, the piston and conn rod are bolted onto the crankshaft first. Then the cylinder is slid over the piston which you position at TDC. I don't recall it being too difficult to do this by easing the ring into the cylinder starting on the ring's semi-diameter and pushing on the ring's opposite side with a stick as you slightly rotate the cylinder in a direction that tends to collapse the ring. It sounds very unwieldy but I did it several times and I am not a mechanic.

[DougR]

Originally Posted by phammy

I have heard that the vent pipe from the filler cap should be routed back into the frying pan air cleaner? Can anyone confirm this because it seems strange to me that I would vent so much smoke back into the air cleaners.

Correct....the crankcase fumes are routed into the air filter/ silencer canister closest to the oil fill, and the hole that the fumes are routed into is downstream of the filter mesh. That way the fumes are consumed in the combustion cycle.

Of course on a normally running engine there aren't many fumes....

The same hole in the front air filter is plugged with a plastic plug.

DougR

[a64pilot]

Originally Posted by phammy

I have heard that the vent pipe from the filler cap should be routed back into the frying pan air cleaner? Can anyone confirm this because it seems strange to me that I would vent so much smoke back into the air cleaners.

You can if you like vent it to the outside of the boat, all older terrestrial Diesels just vented it to the atmosphere, that was the smoke you saw coming from under a farm tractor or maybe an old bus, but don’t vent it just inside of the engine enclose, that smoke is oil smoke and it will make everything nasty and it stinks too.

If an engines oil gets way overfilled say maybe by fuel dilution, the crankshaft will beat the oil into foam, this foam will fill the crankcase and come out of the breather and into the sick side of the engine, it’s fuel so the engine will run away, and it’s real tough to stop, either snatch the hose off or cover the air inlet with something tough, it will damage your hand and will suck a rag in, so a book maybe or piece or wood etc.

[Compass790]

Originally Posted by phammy

I have heard that the vent pipe from the filler cap should be routed back into the frying pan air cleaner? Can anyone confirm this because it seems strange to me that I would vent so much smoke back into the air cleaners.

Personally i would vent it back into aircleaner as I can see advantages with having a bit of top-end lube for the guides & rings.
anyway as another poster pointed out if your rebuild is successful there won't be much smoke

[phammy]

Thanks for all the advice... Ok, I will be sure to vent it back into the air filter once rebuilt.
Wish me luck below deck in the heatwave we're having in the UK.

Have also discovered that the thermostat is badly corroded and it just failed the hot water in a mug test... another part on it's way to me now

[Bilgediver]

Originally Posted by a64pilot

There are piston ring compressors that are inexpensive.
I usually just use my finger tips and or a wood stick like one from a popsicle. That of course only gets one ring at a time and you do have to hold the piston down slightly or it may pop right back out.
A proper ring compressor allows one push to put a piston in, so instead of it taking a minute to do, it’s down to a couple of seconds.
I’ve had issues with ring compressors as if they are just a little bit too tight, they get stuck between the piston and cylinder and doing it by hand I’m certain I’m doing no damage.
But then I enjoy assembling engines too.
I have no experience with your engine, but doubt there are inspection windows that will allow the rods to be removed, usually an engine has to come out and then the oil pan removed, and if your doing all of that, then you may as well go all of the way and measure the bores etc and have them bored out if necessary, that means new pistons etc.
It’s most likely that excessive blow by is coming from the rings, and not the valves, only place it can come from in valves is valve guide wear and wear that bad is extremely unusual

The MD2B does have inspection ports similar to those on larger engines however access to these on a Westerly Centaur is limited.
No need for popsicle Lollypop) sticks as the cylinder block has a chamfer at the lower face and so the piston and rings enter just fine so long as they are correctly positioned and the piston locked firmly in the lower position so it cannot rock.

[Bilgediver]

Originally Posted by phammy

I have heard that the vent pipe from the filler cap should be routed back into the frying pan air cleaner? Can anyone confirm this because it seems strange to me that I would vent so much smoke back into the air cleaners.

The engine is designed for the breather connection to be connected the the rear air cleaner with a short length of correct rubber hose. In fact if you had down this at day 1 you could be sailing now with the cylinder refurbishment deferred till winter. However now that the head is off then it is sensible to deal with it as has been described on this and other forums using a local machine shop that deals in auto (car) or agriculture engines. Usually there is sufficient life in the old valves and seats for a correct grind to Volvo specs so ensure these are shared with the chosen shop as many UK cars have valves and seats of a different angle. You may need new valve guides and the machine shop should be able to deal with these at a reasonable price. Avoid machine shops near the water unless you have deep pockets..

Did you drill out the wee ports in the blocks, you should have got down to a position just below the drain cocks

[Bilgediver]

Originally Posted by Dougtiff

Reminds me of rebuilding a MD 2 in a little back water village in Malaysia back in the 80'S, with the help of a small shop, Hong Kong was the closest Volvo agent, and they didn't have that many part's available, it took forever to obtain part's, so we found way's around the problem, turns out BMW ring's fit, a Volkswagen pump worked, and the local tin smith made a new gasket, by copying the old one, back together, and got more year's out of her, it was a great experience, part of cruising back then, bonding with the local's.

Would need to check the bore to see if standard or an oversize.

[phammy]

Success! I couldn't believe it! I am quite a hands on practical type of person but I was still pretty amazed to hear that beast fire up and sing first try!

Just one minor setback: I sprung a leak in a corroded fuel line thanks to all the bending to fit everything back together. I have repaired this temporarily with rubber fuel pipe from eurocarparts and proper type of fuel pipe clamps that came with the hose. My neighbour said he'd help me make a full set of lines for a permanent fix.

The smoke is far far reduced now and now correctly diverted back into the frying pan filter/silencer.

Ran her for 1 hour and then sea trials on Saturday followed by a longer harder run on Sunday.



When would be appropriate time for the oil change. Does anyone have any advice?
...Should I do a full service or just oil and oil filter only? I have new fuel filters on board but it was only just serviced pre season.



It was a joy to work on this engine - Thanks for all the sound advice

[a64pilot]

I would change oil pretty quick, it’s not going to kill it if you don’t as there just isn’t that much wear metal, but what there is comes off pretty quickly.
I’d say after your first good long hard run. I’d just change oil and filter

[model 10]

I used cheap automotive oil and drained it right after the first run with an airplane engine, it's just a few minutes until it starts to get warm. A Qt of aviation oil is pretty dear and engines often take 12.