At 07:39 PM 4/29/2001, radish150 wrote:
>I installed a wet gauge today to check the real op. I did not pay a whole
>lot of attention to the gauge when I bought it and wish I'd bought another
>one because this one is a 100 lb gauge and is very
>insensitive at low readings.
>
>At any rate, when I first start it up the pressure climbs to about 25 lbs
>at idle, then it falls to about 0 on the gauge after a few minutes. The
>dang gauge is probably useless at low reading though.

Mark, I wouldn't be too concerned personally about what it is at idle
compared to what it is at 2000, 3000, 4000 rpm.  While you're checking
that, though, get hold of another gauge that reads lower
pressures.  Doesn't have to be an "oil pressure" gauge per se.  In any
case, you're talking about a few bucks vs giving up on the whole project
--  you need some real data.  I've heard the rule of thumb quoted of 10 psi
per thousand rpm...

>What do other peoples op readings start out at with cold engine?
>
>The only thing that's left is that relief valve, I suppose it could be
>malfunctioning, but I already cleaned it once.

What about the oil pump?  If the cover plate is worn you'll lose
pressure.  There's a spec in Bentley for the max clearance...

>When I first started it up after installing the gauge, I was happy to see
>that the pressure was respectable, I went away for ten minutes and came
>back and the pressure was about 4-5 on the gauge, a 5
>minute run brought it down to 0. In the opinion of the list gurus, any
>chance that this is a relief valve issue? I thought I'd start it up and
>watch that gauge while idling, to see if it fell suddenly
>or gradually. If it fell gradually, it would logically be a true pressure
>drop, if it fell kind of suddenly, it might be the valve letting go at an
>inappropriate time?

The relief valve is only supposed to come into play when the oil is cold,
to limit maximum pressure to (??) 80 psi or so (??).
I'm not an expert here (!) but I don't see how the valve could "let go" --
it's like the fuel pressure regulator, it only lets through what exceeds
its set point.  If it were leaky then it would cause an across-the-board
reduction in pressure that would gradually increase as the oil warmed and
became thinner -- as would worn bearings etc.

There is one thing you said earlier that makes me nervous -- something
about driving some distance with a quart of Mystery Oil in it?  Again, I'm
no expert but that amount of oil dilution makes me kinda nervous.  I hope
someone who actually knows can say something about how much/how long is
good for unsticking the lifters.  Is there any chance that some of that MMO
is still in there?

Also, perhaps someone knows a way to definitely determine whether the
relief valve is leaking.  Is it possible to put the plunger in upside down
or any such thing?

More questions than answers here, I know.

david

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"