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[quote user="bnsfengineer"][quote]QUOTE: Originally posted by farmer03 maybe you could elaborate some on the crankcase overpressure...? [/quote] Now as far as telling you what gets overpressure on the crankcase. I am not sure what exactly happens, but I will give you an exert out of the mechanical book the railroad gives us. "The diesel engine crankcase normally operates at a vacuum. If pressure is detected in the crankcase, the device will cause the LOW OIL button to protrude for the governor, and the diesel engine will shut down." That all it tells us. Like our instructor told us we are paid to run the trains not to be a machinist.[/quote]All rail sized diesels operate with a slight vacuum in the crankcase; in the case of an EMD, 2" to 5" of water column is what's recommended. (I know we're talking about GE here, but EMD specs are pretty well burned into my brain.) A crankcase overpressure alarm can be from several different things, none of them good. On the less dangerous end of the scale is something like a shot of coolant that flashes to steam. On the upper end of the scale are things like a dropped valve that pierces the piston crown, a cracked piston from a failed piston cooling oil pipe, wrist pin failure, etc. You can roughly gauge the severity of the crankcase explosion by looking at how much oil has been blown out of the safety doors on the crankcase. Little bit=something like a water slug. Whole lot=cracked piston or similar. (This kind is easy to find; fixing them  is usually a different matter---) Early on in it's life (1999), the boat that I run the engine room on went through a series of C/C Kabooms. We were overloading the engines (too much pitch in the prop), and those 16-710's let go on a regular basis and each time was in a big way; we would have oil blown clear up into the second deck overhead. In the late 1980's, I had a boat burn up under me due to a crankcase explosion; this one was a 20-645 that stuck a piston. I make it a point of telling my helpers at safety meetings that a crankcase explosion is the most dangerous situation that they can be faced with in the engine room. Hope this answers a few questions. If anybody can tell me how to do it, I have shots of that 20-645 that I will post for everybody. The shots are on my hard drive.Tommy Towboater
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