Re: Oil Plugs (Spark Plugs, Too!)

[Jeff W <hjr@buffnet.net>]

I'm probably opening myself up to all kinds of retribution for starting
this, but here goes.....

I have always heard, and s*bscribed to the notion, that when threading
steel parts into aluminum, cold is the rule.  Only remove and install
spark plugs into aluminum/magnesium heads when cold. (have lot's of
experience with this from the VW bug days; ever tried to take plugs out
of a hot engine? how long of a breaker bar did you need?)   Same applies
to oil pan, but any fool knows oil is supposed to be warm (& recently
agitated to suspend particles)to drain properly.

Reason, different TCE's (Temperature Coefficient of Expansion) between
AL and steel.  Most respondants to the problem suggested (quite
reasonably) to heat the aluminum and cool the steel.  Depending on the
pitch to diameter ration, this may not always work.  Sometimes this may
compund the problem; don't forget the aluminum/steel is changing
lengthwise in addition to diametrically. (what you gain in diameter may
be offset by binding caused by lengthwise expansion).

Solution to pan plug problem? Don't forget that torque values on Audi's
are always "dry".  Who cleans off pan plugs/threads in pan totally with
degreaser?  Is this even possible?  Result is over-torqued fastener with
correct spec.  Most people don't use a torque wrench on pan plugs, just
snug them up "good & tight" (way over torque needed to hold properly)  I
suspect that cold/cold rule applies in reverse with oil pans; if you
always drain oil hot, you should get oil out and plug back in before pan
cools off.

Of course i gots no probblem wit my steel-panned 80q!

Jeff
'88 80q