[Vwdiesel] Is it weird oil pressure?

Shawn Wright swright at zuiko.sls.bc.ca
Wed Apr 20 23:32:15 EDT 2005

On 20 Apr 2005 at 18:42, Libbybapa at wmconnect.com <Libbybapa at wmconnect.com> wrote:

> Interestingly enough, when I examined the oil pump for wear, I also checked the
> mains.  They looked almost new.  The crank was pristine, and when rotating the
> crank by hand there seemed to be zero play in the rods.  I will try running it
> sans turbo and see if it is related to load, or just boost.  I understand that
> boost is related to load, but once max boost is reached, oil pressure climbs
> with rpm despite load.  If accelerating on the flat, and max boost is reached,
> oil pressure climbs even as one continues to accelerate up a hill following the
> flat.  If just related to load, oil pressure would seem to continue to drop when
> reaching the hill.  The drop is also directly proportional to the amount of
> boost, certainly not an on off situation. Still the big question:  Can someone
> with a gauge reading from the head port on a TD please tell me if their oil
> pressure behaves similarly? or is mine wierd? Andrew

I think running without the turbo is a good idea to isolate the problem. Perhaps if you 
think about the relationship between turbo RPM and oil pressure, this might shed 
some light on things, when you consider that boost & turbo rpm should be directly 
related, nowithstanding wastegate and loss issues. My bet is the turbo bearing 
somehow factors in, perhaps it produces less "backpressure" for the oil feed during 
periods of acceleration of the impellers than when it is in a steady state. When you 
consider how the oil supply is first thing in the oil pressure chain, it is possible that 
subtle changes at the turbo bearing could have a noticeable affect on pressure at the 
head. How is the play in the turbo? Any oil consumption or sign of oil in the cold side 
of the turbo? Just wild speculation of course... :-)

Shawn Wright
'85 Jetta D 
'88 Westy 2.1L, soon to be 1.6TD 5 speed
 (see progress at http://members.shaw.ca/vwdiesels)
'82 Diesel Westy

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