A Happy Exception To The Rule

It’s been a very busy week aboard as we tried to get a handle on what was actually the source of oil in Mosey On’s coolant.  As I readily admitted, this was a question well above my pay grade, so we hired a highly recommended local diesel engine mechanic.  His experience paid-off when he didn’t pursue the most obvious point of failure (a blown head gasket) and instead advised investigating two (less costly) alternatives.  This engine has two oil coolers: one for the engine oil after it circulates through the engine, and a separate one for the transmission connecting the engine to the prop shaft.  Think radiators, but using coolant water instead of air flow to circulate around and cool the oil. These are not terribly complex components, but a failure of a weld or seal would account for the more highly pressurized oil migrating into its cooling water.  [If you’re not a gearhead or your eyes are starting to glaze over at this point, I apologize. You can skip to the last paragraph.]

'In The Belly of the Beast'

John Deere 668D

We removed both units from the boat and took them to be pressure tested for any sign of such leakage.  The results were frustratingly inconclusive: a few bubbles…then nothing from the gear (transmission) cooler, nothing from the engine oil cooler.  Do we go ahead and dismantle much of the engine ($$$) to replace the head gasket or….?  Like a contestant on “Who wants to be a millionaire”, I needed a “Lifeline”.   My wise old local mechanic could not really make a recommendation…In another time, I would not have had any idea where else to turn.  If I didn’t call you, please take no offense!  But in the Internet age, and as a member of the Nordhavn Owner’s Forum, I knew the name of the penultimate mechanical guru for Mosey’s very engine.  I didn’t know if gurus had time for common folk, but I summoned up the courage to call him and relate our tale of woe.  He took my call and before I had even gotten into the full swing of my story he stopped me.

“NOT the head gasket.  It’s the gear cooler.  Common on your engine.  We’ve re-designed the internal seals to cure the problem.  I will send you the white paper and parts list you will need to effect the repair.  Note: we’ve not had a failure of the head gasket on that engine in the twenty-seven years I’ve worked here.”

Getting those and other parts necessary to put it all back together took time on the internet and the help of some knowledgeable and service oriented folks in the parts department of several distributors.   Parts in hand, we re-assembled and remounted the coolers on the engine on Friday.   A test run with fresh clean coolant seems to confirm the diagnosis and treatment.  We cheerfully paid our local mechanic and are indebted for the assistance of many others.

Still not in any rush, but Mosey On is good to go!

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