***Maybe this is a little off the thread. But, what would cause the car to have
good strong oil pressure on start up until running hard for one to one 1/2 hrs.
and then the pressure gradually drops to lower than recommended running levels
(with 20-50weight)? Or what is happening when oil pressure only gradually drops
to
lower than recommended levels when running?
Thanks, D. Michael
Richard Shipman wrote:
> ----> If the flow remains the same, but the pressure drops, this is because
> the thinner oil is leaking past the bearing surfaces faster. The oil
> pressure is monitored at the main distribution oil gallery. From there, it
> takes a long circuitous route through the bearings, oil transfer holes
> drilled throughout the crankshaft and block over to the cam bearings and up
> to the rocker arms, and finally seeps out at each bearing surface and
> returns to the sump via gravity. So, if you are measuring low pressure at
> the main gallery, and each bearing is weeping more oil, and the pressure
> drops to subsequent bearing surfaces further down the oil circuit until at
> worst case, the pressure reaches zero before reaching the furthest bearing
> and you can guess what happens next.
>
> Richard
>
> At 03:53 PM 10/23/99 -0400, you wrote:
> >I guess the other side of this is, what is necessarily wrong with using
> >lower weight oil, even if pressure drops, if the flow remains that same.
> >That is, the bearings would still be lubricated, right?
> >
> >---
> >On 10/23/99, Andy Webster wrote:
> >>The oil pump provides flow...not pressure.
> >>Pressure is provided by the resistance to the shearing forces applied as oil
> >>is forced through small spaces, such as between bearing surfaces, through
> >>filter media and down small galleries. So as bearings wear and the spaces
> >>get bigger the oil flows through with less restraint,like sucking your
> >>thickshake (or partially gelatinated non-dairy gum based beverage) through a
> >>wider straw.
> >>So really thick oil is bad news for a tight tolerance (new) engine and
> >>really thin oil wont build any pressure in an old worn one.
> >>Andy
> >
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