When my Perkins M-30 runs at high rpm, white vapor occasionally comes out of the exhaust. Any thoughts?
Tom Wood responds:
Diesels do smokeand if you have to have a small amount of smoke, white to very pale gray that dissipates quickly is good. This small amount of smoke without much color indicates a healthy burn ratio of air and fuel and that there are no problems with fuel metering or oil burning.
Vast quantities of white smoke, especially under a high load when the engine is hot, can be another story. White smoke can actually be steam. This problem usually would not be indicative of water in the fuel, since that much water mixed in the diesel fuel would cause starting and running problems. However, a small water passage from the coolant side into the combustion chamber would allow the engine to start and run properly, especially when cold, but to issue steam as it warms up.
The cause of such excessive white smoke could be a "blown" head gasket, a small crack in the head, or a crack in a cylinder wall or liner. These problems never get betteronly worse. A salt-water cooled engine makes this passage of water into the combustion chamber difficult to diagnose. A closed, fresh-water cooled system, however, will make the problem obvious if the header tank or reservoir constantly needs to have coolant added after the engine is run. If your issuance of white steam-like smoke continues to worsen, especially if the engine begins to start or run poorly, then you will probably face a teardown of the engine, or at least removal of the head, to diagnose the problem by visual inspection.