Ford's answers to the NHTSA 6.7 Investigation

NewsW wrote:

ricatic wrote:


Condition if both the piston bottom and the follower is "hammered". Considerable scoring and scraping...

I am sending you a PM

Regards

I am reasonably satisfied that the proximate failure point is the piston and bottom --- and it is not likely a secondary failure (e.g. metal chips breaking off from somewhere else then grinding it to smithereens.


Now, as to what caused that failure --- think Ben has the best explanation.

It is a shock load that is unexpected.

But what caused the shock load?

IMHO, the root cause is that metering valve that shuts off fuel to
the intake of the cylinder.

That then creates a vacuum in the cylinder head, that then pulls the
piston off the follower...as the follower continues to ramp down the
cam face.

That creates a cavitation opportunity in both the cylinder head and
the cam cavity as the follower separates from the piston bottom

That then has the follower change directions to move up and slam into
the bottom of the piston....hammering it

Cavitation potential made worse by the brew of potential...no almost
guarantied H2O in there, as all of the OEM measures has less than
100% efficient filters, separators, etc. Another is organic amines,
which is now known to attack DLC, which is one additional possibility
of cavitation removing DLC flakes/microns/etc...aka debris to further
mess up the mating surfaces...made even worse yet with Bio being
mandated by the government and bet everywhere in the next couple years

Since Rick says 'hammered', wonder how many times it took to finally
create debris or bend it, or whatever the mechanism is that then took
out the rest of the pump to spew debris into the plenums and injectors
Possibly...most likely back into the tank via the relief/return lines

There are also some ancillary potential issues with the way the roller
is aligned to the cam and the location of DLC coatings, which indicates
that the designers knew or were chasing some surface issues there.
Plus the very, very poor lube system inside the cam cavity

Surface issues might be friction (natural and of course), but there
might be others too. Like extreme PSI at the contacting points.

Am more confident that one preventive measure, for now, is to disconnect
that metering plug...with the knowledge that the system will continue
to fuel during deceleration and/or EB. So that they need to be both
aware and to take other measures to make up for that lost engine braking