Hi Bruce, I'd certainly start with the crankcase breather; I don't know the engine but it is likely to be just a metal mesh somewhere - often in a pipe running back to the intake side, maybe the manifold or the base of the intake air filter.
He should also check that the pipe itself is not kinked, or blocked (hot oil fumes in cheap rubber pipes can easily cause them to delaminate internally). If he runs the engine, at slow revs, does the pressure at the oil filler tend to 'pulse' or is it quite constant - you can get some idea by resting your hand over the open filler - the former might indicate a ring problem. Smoke is usually down to injectors (so a lack of smoke simply means that they do not need servicing yet) or blocked air filters - however, a broken piston ring can also give similar symptoms to those you described but without necessarily showing up elsewhere. One test for rings is to do a compression check on each cylinder, after the engine has warmed right through and whilst the engine is turning over; you can do this either by whipping all of the injectors out, turning the engine over on the battery, or individually (but the latter does necessitate removing/replacing each injector in turn - so it isn't necessarily a quick job). If running the engine with injectors removed he should take care that the fuel injection pump is not going to spray diesel everywhere [fire hazard] and that dirt cannot enter the fuel line between injector pump and injector - also any copper washers sealing the injector to the head will need to be replaced (or cleaned, and annealed, before refitting). It might also be useful to know when the engine was last serviced - gucky lube oil will quickly block breather filters - as well as oil channels, lube oil filters, etc.; in fact replacing the lube oil and filter is probably the most effective way of extending the useful life of any engine, as well as helping to improve fuel consumption! HTH Trevor -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bruce Napier Sent: 02 March 2009 15:14 To: Canals List Subject: [canals-list] Thorneycroft rocker box oil leak A techie question for once: The chap on the boat currently tied behind me has a 10 yo 3 pot Mitsubishi/Thorneycroft engine that has started blowing lube oil out of the oil filler on top of the rocker box cover. Am I right in thinking this is probably a blocked crankcase breather pressurising the rocker case from below? The engine starts and runs well, with no smoke or other sinister signs. He's not in general very pleased with the engine - the gearbox bolts are so weak, apparently, that the box falls off and has to be refitted about once a year. He describes it as cheap Indian rubbish, which seems a shame for what was a respected name in engines. -- All the best Bruce There are no strangers on the cut, only boaters we've yet to meet. [Non-text portions of this message have been removed] ------------------------------------ Yahoo! Groups Links
