On Wed, 31 Jul 1996, Robert Rhodes wrote:
> Initialy, it showed 100 PSI or so and I thought it would fall and
> the parts became broken in. However, after 300 miles it still shows 100
> PSI, sometimes going off the top of the scale! Even when quite hot the
> guage only falls to 75 pounds at idle and even then is jumping up to 100.
>
> So, how do I test my guage and is this much preasure a problem?
Seems to me that a fairly simple testing fixture could be made up from a
small pipe with an air hose coupler thingy on one end and a fitting to
fit the gauge hose (or sender) on the other end. Can anyone think of any
reason why the gauge would read air pressure differently from oil pressure?
If the problem is in fact high oil pressure (more likely, IMHO, that the
oil pressure would go up than the gauge change, especially considering
the rebuild), chances are there is a problem with your oil pressure
relief valve. Either the valve is firmly stuck shut, or the spring on
the valve is WAY too stiff, or a hydraulic lock has somehow developed
behind the plunger, effectively sticking it shut.
Too-high oil pressure such as this is not a massive problem in normal use.
The excessive pressure costs a very small amount of engine power, but 100
psi oil pressure doesn't protect the bearings any better or worse than 60
psi. The higher pressure will find leaks more easily than stock pressure
as well. But the real danger, if your relief valve is stuck, is the first
time you start it on a cold morning the oil pressure can easily become
high enough to blow the oil filter off of the engine. I have now seen
this happen on both spin-on and canister type filters. You would be
amazed how much driveway six quarts of Castrol can cover.
Hope this helps-
Michael Chaffee
mchaffee@staff.uiuc.edu
[Note new address]
CCSO probably thinks I'm working right now. What do you suppose they think
I'm saying?
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