Monday, March 2, 2009

Root Cause Failure Analysis

One basic precept of my mentor Russell, is that you never treat the symptom you always find the root cause and correct that.

Well, here's the root cause of my engine failure.  It seems a large chunk of the rear main bearing came loose, then got ground up and entered the oil hole in the crankshaft.  This distributed the ground up bearing material through the connecting rods.  Lovely, huh?

This can only result in replacement.  The shaft isn't too bad of shape.  It can probably be machined down nicely after I decide what replacement bearing should be bought.  The worst part is that I spent 20 minutes straight flushing the gunky particles out of the crankshaft.  I blew it out with air, put more cleaning fluid in, then flushed it again.  Still little sparkly bits of bearing were flushed out.  Eventually, I sprayed some seriously strong solvent in it and let it sit.

But that's the end of the story.  It all started with trying to get the timing gear off.  What a chore that was.  A little tension and some heat didn't budge it.  We broke the first puller, and finally succeeded with the second.  Once it started moving it was ok.  I hate to think how hard it will be to get back on.

The bores look good.  Thank goodness.

I lightly scribed an arrow on the pistons pointing front.  The stamped number on the connecting rod points to the left of the engine.

There's a small amount of rust damage to the top of the shaft that retains the half-time gear.  It pulls from the chain, so I don't think it will hurt at all.  I may polish it down a slight amount to make sure there are no high spots.

The engine case is free and clear... waiting to be cleaned.

The combustion chambers are amazingly clean.  Meaning, it didn't get any miles since the last teardown ... or it just ran really clean.

I think it just runs really clean, since the ports are clean as well.  The head gasket wasn't too messed up either.  I probably should replace it.  The bill at Stewart is going up.

1 comment:

  1. A conrod 'oil' clearance of between 0.0015" & 0.0025" is generally acceptable.