Suggestions re: Volvo MD7B please

[Neal]

My 1985 vintage Volvo runs sweetly, though a bit smokily. It starts instantly when warm, and after a few seconds turning over when cold in a UK summer. In the icy cold snap last week, it started easily after I'd squirted some lube oil onto the cylinders.

That's the good bit.

The bad bit is that, when the engine runs contiuously for long periods (say 40 hours), the bilges get a bit oily.

There seem to be two sources of this oil:
- from behind the flywheel. I guess there's a crank shaft seal that's weeping
- a small pool of oil collects under the air filter. There's a pipe from the rocker box to the the air filter, which is black with oil mist.

Oil consumption is almost negligible as measured on the dipstick - but a small volume of oil makes an unsightly mess.

My question is: do I have a real problem, or should I just invest in some rags and bilge cleaner and live with it?

My mechanical engineering skills are of a low order. I've pulled engines out and refitted and re-aligned them, but never undertaken a rebuild.

Any suggestions warmly welcomed.

 

[ccscott49]

Th rear crankshaft oilseal of most engines is a bugger, I dont know how the one on your engine is assembled. but a look at the workshop manual would tell you, if its in a seperate carrier, then it's not a monumental job. But if the crank has to come out it is! The oil being blown out of the breather pipe is more suspect, it could mean ring blowpast, which is overpressuring the crankcase. The fact that it starts easy with a squirt of iol in the cylinders when cold, if it's a swine to start without, is symptomatic of bore/ring wear, which could mean engine re-build time. You need to get a compression test, done to ascertain the state of the bores/rings, then decide what to do after that. If you find the compressions are so, so, then you may think about the oil seal, if it's a crank out job, how long can you live with oily rags and bilge cleaner? IMHO

 

[Neal]

Thanks...a compression test sounds a very sensible suggestion.

The engine starts instantly (certainly within a second of turning the key) when even just slightly warm, or within a few seconds when cold in summer (ie when it hasn't run for the previous 24 hours). This is without oil added to the cylinders.

The engine wouldn't start last week in sub zero temperature, until I added oil, when it started very easily. It has no cold starting aids, other than the decompression lever (ie no glow plugs, no fuel warmer, no 'cigarettes').

 

[scottie]

as the flywheel is at the front you should be able to replace the oil seal insitu main problem may be getting the flywhel of the crankshaft

you may have a cold start device on the underside of the fuel pump
a short 1/2" lever is fitted but was not always connected with a remote cable
worth checking

if your md7 is running ok appart from basic servicing and canging the oil seal
best leave it or replace it as parts are very expensive even by marine standards