Re[2]: [ihc] RE: David's decarbonisation

["ken.dunnington" <ken.dunnington@xxxxxxxxx>]

David Bongo wrote:

DB> This sounds like it's worth trying, but since I have a low milage
DB> rattler (I've put just about 10,000 miles on it, and it didn't have
DB> much more than a break-in period before I got it) what "fix" am I
DB> looking at?

Dave

I'd agree with Hofs and not worry too much about it since you
have a low mile engine with the rattle.  I doubt the rattle is due to
carbon build-up in 10K miles of use unless there is something else
wrong.  10K miles is just not enough fuel to create the large
amounts of hard carbon that lead to a rattle.  With your engine, I'd
say it's far more likely that you have loose tolerances on the fit of
the pistons.  The only fix for this is essentially a rebuild, though
it does relate to the "piston knurling" thread.  But that is a fix for
someone who uses their vehicle(and their time) very differently than
you.

The good news is that, as mentioned previously, piston slap is not a
death knell for a low mile engine.  The resultant noise is normally
just an annoyance not a warning that repair is necessary.

Just pity the folks who purchased a $35K vehicle that had this noise
after about 1K miles and were told it would not be fixed under
warranty.  The manufacturer chose not to warranty due in part to the
fact that these engines would likely last over 100K miles, albeit
a noisy 100K.

Piston slap generally is loudest on start-up with the engine at
ambient.  Because the pistons will expand more than the cylinder will,
the clearance will reduce as the engine warms to operating temp.  Some
engines only slap when cold, they are quiet after warm-up due to this.
Forged pistons are more likely to exhibit this behavior as they have
a higher coefficient of thermal expansion than cast and thus have a
larger "cold" tolerance specified than cast.

Ken