From: Vernon Tuck (vtuck@tucklings.com)
Date: Tue Aug 10 2004 - 19:19:46 PDT
In diesel engines black smoke is unburned fuel.
Bluish white smoke from burned engine oil may be hard to distinguish from
white smoke caused by water getting into the combustion chamber.
It may be that you pushed a newly rebuilt engine a little too hard and one
or more rings didn't seat properly. However, I would think this were the
case you'd have persistent blue/white smoke and not just sporadically.
With diesel engines there is an issue called "cavitation". It is a real
concern. I won't go into a dissertation on what causes it but, simply put,
it amounts to pin holes penetrating from the water jackets into the
combustion chamber. Sooner or later it leads to a catastrophic engine
failure.
So let's hope you don't have it. The other thing that comes to mind is that
one of the head gaskets is going south.
It would not cost a great deal to have your engine oil and coolant sampled
at a big truck shop. If you have oil in your coolant and/or coolant in your
oil you may have a serious problem caused by cavitation. I would suggest
you search the internet to find out how many 6.5 owners have had this
problem, if any.
It was an extremely common problem with the 1988 - early 90s Ford 7.3
diesels. That's often why those model Ford trucks get dumped for cheap.
I need to disclaim that I have no experience with the GMC 6.2 or 6.5
engines. But I've been driving all kinds of diesel cars and trucks for
years.
Diesels require specially rated coolant (antifreeze). Ignore this at your
peril.
Hope this isn't too alarmist and that you don't have to travel that bumpy
road.
Of the three possible problems listed above I'd consider a bad head gasket
to be the least expensive.
Vernon
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