How Much Oil Do you Use?

Derek Pulvino dbpulvino at
Wed Jan 28 15:58:08 EST 2004


Finally getting back around to this and it seems pretty logical.  Just 
wondering, is "blow-by" a symptom of bad rings only (or maybe more 
accurately a phenomenom originating in the block), or can sufficient 
pressure move past the valve guides and seals and then work through the oil 
return galleys...resulting in an air/oil mixture through the breather 

So I guess the short question is, can blow-by come from the head as well as 
the block, or only the block.

> >
> > But still didn't answer the question, why is this happening.  What are
> > potential culprits?  How can I be sure it's the head, and not turbo 
> > or a problem with the crankcase vent system?  I figure leak down will 
> > me block vs. head, but how could I tell about the turbo seals or if the
> > cranckcase vent system is my culprit?
>There are no common, contact type, elestrometeric rotary shaft seals, just
>labyrinth seals across which there is positive gas pressure to the return
>oil passages.  Bearing wear causes seal clearance wear with resultant oil
>blow by.  If the turbo to IC and the IC to IM hoses are heavily oil wetted
>you have either a piston blowby problem coming thru the crankcase breather
>system to the turbo fresh air input (the compressor wheel should be oil
>coated), or the turbo bearings are shot, (the compressor wheel not oil
>Do a compression check, first dry and second with oil injected into the
>cylinder to better seal any ring leakage.  If no dif, you have a valve
>problem.  Incresesd comp points to a ring problem.
>Tis good to isolate the source of your problem, such that it is easier
>monitored, but DFI if IAB!

Not sure this is absolutley black and white.  Varying degrees of "broke," 
consumption, and tradeoffs therein.

Derek P


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