6V53 Minor Runaway - Maybe

[DCMY #92]

I started one of my 1963 6V53Ns yesterday after cleaning the heat exchanger, servicing the raw water pump, replacing the coolant, etc. The engine had not run in a few months so I confirmed the injector racks were free - all good there.

The engine started normally and idled about 550 rpm with slight hunting. While looking for leaks as she warmed up I noticed a white vapor exiting the crankcase vent pipe. The vapor was not moving from the vent pipe overly rapid and was easily sucked into the inlet silencer. After a few minutes a burst of oil droplets and white vapor suddenly spurted out of the vent tube with a whooshing sound, splattering the engine room wall with oil droplets, and the engine now at 1000 rpm. This all happened in seconds.

There was no exhaust smoke on startup or while idling at 1000 rpm after the event. I don´t know about during the event because I was in the engine room. The engine idled with no hunting at 1000 rpm while I looked it over for anything unusual before shutting it down.

I removed the valve covers, inlet silencer, silencer-to-blower adaptor and debris screen. I measured the head temperature between injectors and it had only gotten up to 108F. The white vapor was just visible slowly rising out of the oil drain holes in the head.

Inspection of the dipstick did not indicate any water contamination. Also no obvious unusual slobbering from the air box drains. The engine shut down normally with no indication of any sticking rack. All racks were free and normal after shutdown.

The engine has about 300 hours since new cylinder kits were installed several years ago. The blower were overhauled during the mid ´80s. I´ve attached a couple of photos of the blower after I shut the engine down. The endplates look cleaner than the other surfaces to me. Maybe because leaking oil is washing them? I did not observe the blower rotors while the engine was running to see if liquid oil was visible.

I hope to get advice here and BoatDiesel before I start the engine again. I´m thinking that maybe a blower end seal failed causing a semi-runaway, but I don´t have any experience regarding what blower oil leak symptoms would be.

Alternatively, maybe something failed in the governor. This engine´s governor has never been as stable and the other engine at idle. It has always required a slightly higher idle speed to avoid stalling when shifting from neutral. Again, I have no experience on which to base an opinion about governor failure. I recall from the ´80s work that the governor has to be disassembled to remove the blower, so I guess both of my initial thoughts can be proven of eliminated by starting down that road.

Any advice will be very much appreciated - especially if I´m off in the ditch suspecting the blower or governor.

 

[DCMY #92]

Maybe I should mention that this engine´s crankcase ventilation vent pipe comes directly from the port-side valve cover and discharges into the aft end of the blower inlet silencer with no oil separation other than a simple baffle inside the valve cover. I suspect this is the cause of allot of the oil contamination in the blower. Also, there is no air filter so crud accumulation in the inlet silencer, blower and air box is unavoidable.
These are the same engines Hatteras installed in the Vietnam era river patrol boats but without the jet drive.

 

[cww]

This is exactly why everybody with detroits gets airseps. I'm sure they make a kit for your engine, my boat has them, and in addition to much cleaner engine rooms, they greatly reduce the risk of a runaway by routing the oil that's normally circuiting through the intake straight back into the crankcase. It's just a much better mousetrap.