worn bearing cause low oil pressure?

On 6/6/2010 11:23 PM, Nomen Nescio wrote:
> I noticed low oil pressure when the revs are down.
> So I get out the workshop manual, and it lists among the
> possible causes "worn bearings". How is it so?
> I can't see that oil is pumped through the bearings in
> a closed fashion, such that worn bearing would reduce
> the back pressure.
>

Yes, a modern engine does use a closed loop oil system. If it didn't
you would have to replace lots of oil every time you drove the car.

The oil pump pushes against resistance. If the resistance to flow is
substantially lowered, the pressure in the system will drop. The
bearing clearances definitely affect the flow and hence the pressure.
The concern is that the flow may then end up short circuiting, and not
getting into some passages, taking the road of least resistance through
the main and rod bearings. Lots of flow for them, but not enough for
other important places.

"Don Stauffer" > wrote in message
...

> Yes, a modern engine does use a closed loop oil system. If it didn't you
> would have to replace lots of oil every time you drove the car.
>
> The oil pump pushes against resistance. If the resistance to flow is
> substantially lowered, the pressure in the system will drop. The bearing
> clearances definitely affect the flow and hence the pressure. The concern
> is that the flow may then end up short circuiting, and not getting into
> some passages, taking the road of least resistance through the main and
> rod bearings. Lots of flow for them, but not enough for other important
> places.

Pressure is little more than a parameter of oil flow in traditional sleeve
or
insert bearing engines as far as lubrication goes.

If you have a roller or needle bearing engine, as Porsche had some 60
years ago, the pressure may not mean very much as long as the oil flow
through the bearings is adequate. (Those cars, IIRC, didnt mess around
with hydraulic valve lifters either.)

Here is an interesting link showing what Timken did with an engine
converted to roller bearings:
http://engineeringtv.com/video/Rollerized-Engines

"Don Stauffer" > wrote in message
...

> Yes, a modern engine does use a closed loop oil system. If it didn't you
> would have to replace lots of oil every time you drove the car.

There's nothing "modern" about such a system. They've been in place for over
100 years.

--
Regards,
Noddy.

On 6/7/2010 5:23 PM, Noddy wrote:
> "Don > wrote in message
> ...
>
>> Yes, a modern engine does use a closed loop oil system. If it didn't you
>> would have to replace lots of oil every time you drove the car.
>
> There's nothing "modern" about such a system. They've been in place for over
> 100 years.
>
> --
> Regards,
> Noddy.
>
>
True. But some engines in 1910 may have used older designs. Some had
individual oil cups at each bearing surface, and these were open- oil
was wasted and not returned with a pump. Some had no pump, merely a
reservior high up and gravity feed. No return/re-use of oil- open system.

Didn't Chevy go to pressurized rods only around 1940 or so?

Don Stauffer wrote:
>
> On 6/7/2010 5:23 PM, Noddy wrote:
> > "Don > wrote in message
> > ...
> >
> >> Yes, a modern engine does use a closed loop oil system. If it didn't you
> >> would have to replace lots of oil every time you drove the car.
> >
> > There's nothing "modern" about such a system. They've been in place for over
> > 100 years.
> >
> > --
> > Regards,
> > Noddy.
> >
> >
> True. But some engines in 1910 may have used older designs. Some had
> individual oil cups at each bearing surface, and these were open- oil
> was wasted and not returned with a pump. Some had no pump, merely a
> reservior high up and gravity feed. No return/re-use of oil- open system.
>
> Didn't Chevy go to pressurized rods only around 1940 or so?

I believe it was 1953 maybe '52. The 216 six had rods with a cup like
thing on the rods that dipped into the oil in the pan and that
lubricated the rods, pistons and piston pins. I think it was the mid
30's when they started using an oil pump but the pump only lubricated
the valve train and the main bearings. The rest was splash lubrication.

-jim

"Don Stauffer" > wrote in message
...

> True. But some engines in 1910 may have used older designs. Some had
> individual oil cups at each bearing surface, and these were open- oil was
> wasted and not returned with a pump.

It doesn't have to be a pressurised system for it to be a "closed" system.

Most car engine lubrication systems have been "closed" since the year dot,
and it'd actually be difficult to find one that wasn't. For example, the
Model T Ford, which first appeared in 1908 and was the most popular car in
the world in it's day, used cups on the bottom of the connecting rods to
"scoop" oil to lubricate the rod bearings as the rods revolved around and
dipped into the oil in the pan. This oil would then eventually be flung out
from between the bearing and crank journal and fall back into the pan for
the whole process to be repeated.

On the other hand, some types of machinery use "open" lubrication systems,
or "total loss oiling systems" as they're known, whereby lubricating oil is
held in a reservoir and runs through the system by gravity, and falls out
the bottom as waste.

Such systems work fine on stationary equipment where it can be collected in
a drip tray, but is largely impractical on moving cars.

--
Regards,
Noddy.

Noddy > wrote:
>
>On the other hand, some types of machinery use "open" lubrication systems,
>or "total loss oiling systems" as they're known, whereby lubricating oil is
>held in a reservoir and runs through the system by gravity, and falls out
>the bottom as waste.
>
>Such systems work fine on stationary equipment where it can be collected in
>a drip tray, but is largely impractical on moving cars.

I think I had an MGB like this once.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Noddy wrote:
>
> "Don Stauffer" > wrote in message
> ...
>
> > True. But some engines in 1910 may have used older designs. Some had
> > individual oil cups at each bearing surface, and these were open- oil was
> > wasted and not returned with a pump.
>
> It doesn't have to be a pressurised system for it to be a "closed" system.
>
> Most car engine lubrication systems have been "closed" since the year dot,
> and it'd actually be difficult to find one that wasn't. For example, the
> Model T Ford, which first appeared in 1908 and was the most popular car in
> the world in it's day, used cups on the bottom of the connecting rods to
> "scoop" oil to lubricate the rod bearings as the rods revolved around and
> dipped into the oil in the pan. This oil would then eventually be flung out
> from between the bearing and crank journal and fall back into the pan for
> the whole process to be repeated.
>
> On the other hand, some types of machinery use "open" lubrication systems,
> or "total loss oiling systems" as they're known, whereby lubricating oil is
> held in a reservoir and runs through the system by gravity, and falls out
> the bottom as waste.
>
> Such systems work fine on stationary equipment where it can be collected in
> a drip tray, but is largely impractical on moving cars.

Well it wasn't entirely impractical. The oil was dirt cheap and dripping
it out onto the roadway helped keep the dust down.

-jim


>
> --
> Regards,
> Noddy.

Noddy wrote:
> "Don Stauffer" > wrote in message
> ...
>
>> True. But some engines in 1910 may have used older designs. Some had
>> individual oil cups at each bearing surface, and these were open- oil was
>> wasted and not returned with a pump.
>
> It doesn't have to be a pressurised system for it to be a "closed" system.
>
> Most car engine lubrication systems have been "closed" since the year dot,
> and it'd actually be difficult to find one that wasn't. For example, the
> Model T Ford, which first appeared in 1908 and was the most popular car in
> the world in it's day, used cups on the bottom of the connecting rods to
> "scoop" oil to lubricate the rod bearings as the rods revolved around and
> dipped into the oil in the pan. This oil would then eventually be flung out
> from between the bearing and crank journal and fall back into the pan for
> the whole process to be repeated.
>
> On the other hand, some types of machinery use "open" lubrication systems,
> or "total loss oiling systems" as they're known, whereby lubricating oil is
> held in a reservoir and runs through the system by gravity, and falls out
> the bottom as waste.

Harley Davidson still uses this system...!

>
> Such systems work fine on stationary equipment where it can be collected in
> a drip tray, but is largely impractical on moving cars.
>
> --
> Regards,
> Noddy.
>
>
>

"jim" <"sjedgingN0Sp"@m@mwt,net> wrote in message
.. .
:
:
: Noddy wrote:
: >
: > "Don Stauffer" > wrote in message
: > ...
: >
: > > True. But some engines in 1910 may have used older designs. Some had
: > > individual oil cups at each bearing surface, and these were open- oil
was
: > > wasted and not returned with a pump.
: >
: > It doesn't have to be a pressurised system for it to be a "closed"
system.
: >
: > Most car engine lubrication systems have been "closed" since the year
dot,
: > and it'd actually be difficult to find one that wasn't. For example,
the
: > Model T Ford, which first appeared in 1908 and was the most popular car
in
: > the world in it's day, used cups on the bottom of the connecting rods to
: > "scoop" oil to lubricate the rod bearings as the rods revolved around
and
: > dipped into the oil in the pan. This oil would then eventually be flung
out
: > from between the bearing and crank journal and fall back into the pan
for
: > the whole process to be repeated.
: >
: > On the other hand, some types of machinery use "open" lubrication
systems,
: > or "total loss oiling systems" as they're known, whereby lubricating oil
is
: > held in a reservoir and runs through the system by gravity, and falls
out
: > the bottom as waste.
: >
: > Such systems work fine on stationary equipment where it can be collected
in
: > a drip tray, but is largely impractical on moving cars.
:
: Well it wasn't entirely impractical. The oil was dirt cheap and dripping
: it out onto the roadway helped keep the dust down.
:
: -jim
:
:
: >
: > --
: > Regards,
: > Noddy.

I had wondered what system they used on the magna. Now I know. "total loss
oiling systems"

--
Brad Leyden
6° 43.5816' S 146° 59.3097' E WGS84
To mail spam is really hot but please reply to thread so all may benefit (or
laugh at my mistakes)
>
>