Re: all BMW oil holes in pistons

[Rob Clark <rclark@xxxxxxxxxx>]

Is there any relatively easy way to check this?  Does the same
buildup tend to occure other places, maybe where I could see
it with only having to take the valve-cover off? I have a high-
milage engine (280K miles, 180K since rebuild), which I would
guess would make it a canditate for such build-up. I know the 
engine won't last forever, but if it is something that can be
cured if caught in time, I would prefer to check it now than
find out the hard way!

Thanks!

- --Rob
87 325is

>From: bmrfamly@domain.elided (Dan, Marilyn, Anathea, & Phil Patzer)
>Date: Mon, 27 Jul 1998 07:26:36 -0700
>Subject: all BMW oil holes in pistons
>
>  I am continually amazed at the "Kreosote" (by-product of water vapor &
>oil vapor) I find on head bolts, and in the head bolt holes within the head
>when replacing seeping head gaskets.
>  I always try talking the owners into replacing the piston rings as the
>same chemical process that fills the head bolt holes also fills the oiling
>holes within the third ring groove (the oiling ring) on the sides of the
>pistons.
>  I always DRILL out the holes and often have to use the drill-press,
>instead of the hand drill, as the Kreosote plugs are so solid.
>  The purpose of these holes is to supply oil to the oiling rings (the
>piston bottom acts like a funnel capturing oil sprayed from the sides of
>the connecting rod bearings at their crank journals).  The oiling ring has
>calibrated openings and two "squeegie" edges.  Often these are multiple
>piece devices which eliminates the large end gap if the segments are
>mounted properly.
>  Inadequate oil delivery because of plugged holes leads to rapid cylinder
>wall deterioration.  This is indicated by loss of "honing" marks and the
>presence of vertical scoring.
>  Caught early enough, the cylinders can be honed, and the rings, and crank
>bearings can replaced with hood and block in place.  Severe scoring will
>not hone out, but requires boring for larger pistons.  This is very costly
>and the block must be pulled.n be honed, and the rings, and crank
>bearings can replaced with hood and block in place.  Severe scoring will
>not hone out, but requires boring for larger pistons.  This is very costly
>and the block must be pulled.

 

------------------------------