Oil Pressure Assumptions.....

I'm trying to increase the oil pressure in a 96 Nissan Sentra 1.6 Liter
engine. The oil light comes on with engine hot, idling in Drive, goes
out when put in neutral. I just changed the oil from 10w-30 to 20-w-50,
and the light has not come on again But it's still making a
lot of valve noise when hot, so pressure seems to still be aproblem. I
had a mech put a gauge on it and was reading ZERO when hot and idling,
and only 15 when revved to about 1500. I know, don't drive it.

I think there is still something else that can be done to improve the
oil pressure. I have received conflicting predictions about whether the
op wouild be affected by it.

There is supposed to be an "oil pressure regulator" valve on the engine
block, which is covered by the oil filter. When changing the filter, I
noticed, on the engine block, there is only a hole with a spring
resting loosely inside. No cap, poppet, lid, etc covering the hole.
Just a wide open bypass hole. Looks like the "op reg valve" broke off
and went somehwere, I hope into the garbage after an oil change, and
not up into the engine !! don't know.

I have orderd the part from Nissan and will get it tomorrow.

My question is whether the bypass being wide open constanly is
affecting the op.

My ASSUMPTIONS (some redundant, admitted) are :

A. The oil flows from the pump directly up to the filter inlet
(unless pump bypass is stuck open!)


B. Once the oil is entering the oil filter area, most, or all of it,
is going right into the open bypass hole, and ignoring the filter,
since it is getting resistance there. Maybe 10 percent of the oil is
going thu the filter if rpms are high enough.

C. The oil pressure is its highest immediately after it leaves the
pump, and DECREASES as it encounters bleedoff opportunities on its
journey through the engine.

D. The oil pressure AFTER an obstruction, like an oil filter, will be
lower than the oil press in front of the obstruction.

E. An obstruction acts to INCREASE the oil pressure in the oil in
front of (before) the obstruction. (Same as D, I know)

F. The idiot light op sensor is located AFTER the oil filter and also
AFTER the bypass hole.

G. The oil flowing thru the filter and thru the bypass hole end up in
the same channel, the oil from both sources recombines somewhere, like
two streams feeding into a river, then goes on its way up to the head.


H. Installing the "oil pressure regulator valve" will INCREASE the op
BEFORE the oil filter, but may actually DECREASE the op after the
filter, since now the oil will be forced into the filter (obstruction)
intead of just flowing thru the wide open bypass hole as before. BTW
this is a new, clean unplugged filter).


Thanks. Some folks have told me installing the new bypass valve
will boost the oil pressure, even AFTER the filter, but I don't see
how. I hope it does, but I don't see how.


Thanks for any replies !!

Sounds like it is time for a new engine. How many miles on it?

Caprice85 wrote:
> I'm trying to increase the oil pressure in a 96 Nissan Sentra 1.6 Liter
> engine. The oil light comes on with engine hot, idling in Drive, goes
> out when put in neutral. I just changed the oil from 10w-30 to 20-w-50,
> and the light has not come on again But it's still making a
> lot of valve noise when hot, so pressure seems to still be aproblem. I
> had a mech put a gauge on it and was reading ZERO when hot and idling,
> and only 15 when revved to about 1500. I know, don't drive it.
>
> I think there is still something else that can be done to improve the
> oil pressure. I have received conflicting predictions about whether the
> op wouild be affected by it.
>
> There is supposed to be an "oil pressure regulator" valve on the engine
> block, which is covered by the oil filter. When changing the filter, I
> noticed, on the engine block, there is only a hole with a spring
> resting loosely inside. No cap, poppet, lid, etc covering the hole.
> Just a wide open bypass hole. Looks like the "op reg valve" broke off
> and went somehwere, I hope into the garbage after an oil change, and
> not up into the engine !! don't know.
>
> I have orderd the part from Nissan and will get it tomorrow.
>
> My question is whether the bypass being wide open constanly is
> affecting the op.

<snip>

ABSOLUTELY! I don't have specific knowledge of Nissans, but on engines
that I have worked on, the OPRV works like this; when oil pressure is
above a specified value, usually around 50-80 PSI depending on specific
engine, the valve opens and allows oil to bypass the normal galleries
and dumps it straight back into the oil pan. (well, maybe not straight
- on a Studebaker, for instance, the OPRV also provides lubrication for
the timing gears. But I digress, and you get the idea.) The whole
purpose of this is to bleed off oil pressure when it could be too high,
such as immediately after a cold start or excessively high RPM
operation so that you don't blow apart oil filters, wash the babbitt
off of your bearings, etc.

At hot idle, oil pressure is almost never above the opening pressure of
the OPRV, and the OPRV should be fully closed. This is almost
certainly the source of your problem. In fact I'd be surprised if you
had any measurable oil pressure under the circumstances you describe!

As an aside, this is yet another reason why ALL cars should be fitted
with oil pressure GAUGES not idiot lights... who knows how long this
car was run with marginal oil pressure before anyone saw/heard a
problem...

Once you get the new OPRV parts and have them installed, leave the
gauge hooked up and let us know what you find. I'm guessing you will
be pleasantly surprised by the results, and I hope that you don't have
any issues with this engine caused by being run with such low oil
pressure.

The only thing that concerns me is the location you specified for the
OPRV. From your description it could either be as I described, or it
could be a bypass valve which opens when the pressure *drop* across the
oil filter element gets too high (i.e. it's clogged) in which case
replacing same will restore proper operation of your oil filter but may
not improve your oil pressure. I'm hoping it's the former, and the
nomenclature that they used ("pressure regulator") makes me somewhat
hopeful for you...

good luck,

nate

John S. wrote:
>
> After you replace that valve you should consider hooking up an oil
> pressure gauge to find out if the pressure is truly within spec.
>
> I could start ranting about how useful the three basic gauges are for
> monitoring your car's performance. But as cars and their interiors
> have been downsized some features have given way. I would trade that
> oversized tach for an oil pressure and voltage meter (or ammeter) in a
> heartbeat.
>
> The last car I had that was set up for full gauges was a 1988 Volvo
> 740. It had slots for gauges within the very readable instrument
> panel.
>

Downsized? Not in the US.

I think the gauges went away because they revealed any misperformance of
the engine and caused more warranty claims. Also some users didnt
understand them and would bring the vehicles in for stuff that was not
an issue.

Im sure the OEMs have no issue with you installing one after the
warranty period is up.

--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

I hope you will post what you find out when you get the OPR.
I would really like to know where the ball, or whatever, went (that was a
part of
this pressure loaded device.)

IIFC, the old Fords (390 type blocks )had a pressure regulator built into
the oil pump. Sometimes the springs would relax, and the oil pressure would
drop too low. A
new spring, or just stretching the old one, would often revive the oil
pressure.

dnoyeB wrote:
> John S. wrote:
> >
> > After you replace that valve you should consider hooking up an oil
> > pressure gauge to find out if the pressure is truly within spec.
> >
> > I could start ranting about how useful the three basic gauges are for
> > monitoring your car's performance. But as cars and their interiors
> > have been downsized some features have given way. I would trade that
> > oversized tach for an oil pressure and voltage meter (or ammeter) in a
> > heartbeat.
> >
> > The last car I had that was set up for full gauges was a 1988 Volvo
> > 740. It had slots for gauges within the very readable instrument
> > panel.
> >
>
> Downsized? Not in the US.

Sure it is, look at the instrument panel. It's smaller and filled up
with outsized and useless tachometer, and a travel information screen.
With most cars using front wheel drive one would expect to have more
legroom, but that's saken up by a console filled with all manner of
cupholders, cd racks switches and the like. The interior of most
american cars is smaller than it once was although car makers do make
more efficient use of the remaining space.


>
> I think the gauges went away because they revealed any misperformance of
> the engine and caused more warranty claims. Also some users didnt
> understand them and would bring the vehicles in for stuff that was not
> an issue.

Naw, cars as a group are far far more reliable than 25 or more years
ago. It is nothing to have a car go 300,000 miles and at least one car
maker gives a 100k mile warranty. Gauges disappeared because not
enough people really used them, cars were shrinking in size and car
makers could use the space for other more useful things like oversized
tachs, full entertainment centers and automotive compasses.

>
> Im sure the OEMs have no issue with you installing one after the
> warranty period is up.

Try to find the room to fit an oil and amp gauge in or alongside a
modern instrument panel. Sure you can tack a plastic or metal bezel to
the bottom of the dash, but that looks like a typical backyard
modification.

John S. wrote:

>
>
>
> Sure it is, look at the instrument panel. It's smaller and filled up
> with outsized and useless tachometer, and a travel information screen.
> With most cars using front wheel drive one would expect to have more
> legroom, but that's saken up by a console filled with all manner of
> cupholders, cd racks switches and the like. The interior of most
> american cars is smaller than it once was although car makers do make
> more efficient use of the remaining space.
>
>
>
>>I think the gauges went away because they revealed any misperformance of
>>the engine and caused more warranty claims. Also some users didnt
>>understand them and would bring the vehicles in for stuff that was not
>>an issue.
>
>
> Naw, cars as a group are far far more reliable than 25 or more years
> ago. It is nothing to have a car go 300,000 miles and at least one car
> maker gives a 100k mile warranty. Gauges disappeared because not
> enough people really used them, cars were shrinking in size and car
> makers could use the space for other more useful things like oversized
> tachs,

You just said "It's smaller and filled up with outsized and useless
tachometer" and now you say more useful things like a oversized tach?

Tell me how useful a tach is on a automatic transmission car?
Give me a oil pressure gauge and a volt meter any day. Then give
me the tach.



full entertainment centers and automotive compasses.
>
>
Compass? Men never get lost..........

>> Im sure the OEMs have no issue with you installing one after the
>>warranty period is up.
>
>
> Try to find the room to fit an oil and amp gauge in or alongside a
> modern instrument panel. Sure you can tack a plastic or metal bezel to
> the bottom of the dash, but that looks like a typical backyard
> modification.
>
I remember back in the 60's seeing the 3 pack combo of round gauges for
oil, water, volts hanging under the dash. It was either cool or ugly
depending on your point of view. Of course that was in pre "pimp my
ride" days. On some cars, there were optional dashes with real gauges.
On some cars your can retro fit them in.

Bob



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"Bob Urz" > wrote in message
...
>
>
> John S. wrote:
>
>>
>>
>>
>> Sure it is, look at the instrument panel. It's smaller and filled up
>> with outsized and useless tachometer, and a travel information screen.
>> With most cars using front wheel drive one would expect to have more
>> legroom, but that's saken up by a console filled with all manner of
>> cupholders, cd racks switches and the like. The interior of most
>> american cars is smaller than it once was although car makers do make
>> more efficient use of the remaining space.
>>
>>
>>
>>>I think the gauges went away because they revealed any misperformance of
>>>the engine and caused more warranty claims. Also some users didnt
>>>understand them and would bring the vehicles in for stuff that was not
>>>an issue.
>>
>>
>> Naw, cars as a group are far far more reliable than 25 or more years
>> ago. It is nothing to have a car go 300,000 miles and at least one car
>> maker gives a 100k mile warranty. Gauges disappeared because not
>> enough people really used them, cars were shrinking in size and car
>> makers could use the space for other more useful things like oversized
>> tachs,
>
> You just said "It's smaller and filled up with outsized and useless
> tachometer" and now you say more useful things like a oversized tach?
>
> Tell me how useful a tach is on a automatic transmission car?
>snip<
Bob, I believe when John said "car makers could use the space for other
more useful things like oversized tachs, full entertainment centers and
automotive compasses", he was saying so in jest, merely being sarcastic.
Surely, you guys are in agreement--or so it seems to me. s

Bob Urz wrote:
> John S. wrote:
>
> >
> >
> >
> > Sure it is, look at the instrument panel. It's smaller and filled up
> > with outsized and useless tachometer, and a travel information screen.
> > With most cars using front wheel drive one would expect to have more
> > legroom, but that's saken up by a console filled with all manner of
> > cupholders, cd racks switches and the like. The interior of most
> > american cars is smaller than it once was although car makers do make
> > more efficient use of the remaining space.
> >
> >
> >
> >>I think the gauges went away because they revealed any misperformance of
> >>the engine and caused more warranty claims. Also some users didnt
> >>understand them and would bring the vehicles in for stuff that was not
> >>an issue.
> >
> >
> > Naw, cars as a group are far far more reliable than 25 or more years
> > ago. It is nothing to have a car go 300,000 miles and at least one car
> > maker gives a 100k mile warranty. Gauges disappeared because not
> > enough people really used them, cars were shrinking in size and car
> > makers could use the space for other more useful things like oversized
> > tachs,
>
> You just said "It's smaller and filled up with outsized and useless
> tachometer" and now you say more useful things like a oversized tach?


Sarcasm sometimes doesn't come across very well in writing, although
the comment about entertainment centers in automobiles might give a
hint about my feelings. Or more plainly, tachometers of any size are
little more that visual entertainment for virtually all drivers. The
needle goes up, the needle goes down but the useful information it
might provide in a very few situations goes unnoticed.

>
> Tell me how useful a tach is on a automatic transmission car?
> Give me a oil pressure gauge and a volt meter any day. Then give
> me the tach.
>
>
>
> full entertainment centers and automotive compasses.
> >
> >
> Compass? Men never get lost..........
>
> >> Im sure the OEMs have no issue with you installing one after the
> >>warranty period is up.
> >
> >
> > Try to find the room to fit an oil and amp gauge in or alongside a
> > modern instrument panel. Sure you can tack a plastic or metal bezel to
> > the bottom of the dash, but that looks like a typical backyard
> > modification.
> >
> I remember back in the 60's seeing the 3 pack combo of round gauges for
> oil, water, volts hanging under the dash. It was either cool or ugly
> depending on your point of view. Of course that was in pre "pimp my
> ride" days. On some cars, there were optional dashes with real gauges.
> On some cars your can retro fit them in.

Oh, yeah, the little chrome three gauge bezel looked kinda cool to more
than one teenage guy in the 1960's. My college car, a 1959 Morris
Minor had one gauge - fuel. Temperature and oil pressure were idiot
lights on the speedo. OTOH most of the older cars I owned prior to
that had a full complement of useful gauges. As did a 1972 Ford F-250.

I have got to ask...what does pimping a ride mean given that a pimp and
the business he engages in are not exactly pleasant or savory.

John S. wrote:
>
> Try to find the room to fit an oil and amp gauge in or alongside a
> modern instrument panel. Sure you can tack a plastic or metal bezel to
> the bottom of the dash, but that looks like a typical backyard
> modification.
>

Man, you guys need a Firebird.
Comes factory with full gauges.
You can get an aftermarket a-pillar "pod" for more gauges.
And the dash vents just happen to hold 2 5/8 gauges.
(they're round...)

Ray