Should oil in pressure line for gauge go all the way to the gauge?

jim <"sjedgingN0Sp"@m@mwt,net> wrote in
:

>
>
> Tegger wrote:
>>
>> "hls" > wrote in
>> :
>>
>> >
>> > "dr_jeff" > wrote in message
>> >> Why would having the oil go all the way up to the gauge be a big
>> >> deal? Would there always be oil in the line?
>> >
>> > It wouldnt normally make much difference. If the line, partially
>> > filled with air,
>> > experienced heating or cooling, I guess the expansion or
>> > contraction of the air could be more of a factor than it would be
>> > with a tube filled with oil alone.
>> >
>>
>> Air is compressible. Oil is not. Air in the line will result in a
>> falsely low gauge reading. At least that's what happened to me many
>> years ago when I added such a device to my car.
>
> How did you make the leap from air is compressible to it will
> result in
> a falsely low gauge reading? You say that as if everyone is supposed
> to automagically see the connection.
>
> -jim
>

most gauges are dampened so the air is a non issue, and besides every
one I have ever had had air in the line there is no way to keep it out,
every time you shut it off it will drain back and have some air on
restart. KB

--
THUNDERSNAKE #9

Protect your rights or "Lose" them
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--- news://freenews.netfront.net/ - complaints: ---

"jim" <"sjedgingN0Sp"@m@mwt,net> wrote in message
...
>
>
> Tegger wrote:
> >
> > "hls" > wrote in
> > :
> >
> > >
> > > "dr_jeff" > wrote in message
> > >> Why would having the oil go all the way up to the gauge be a big
> > >> deal? Would there always be oil in the line?
> > >
> > > It wouldnt normally make much difference. If the line, partially
> > > filled with air,
> > > experienced heating or cooling, I guess the expansion or contraction
> > > of the air could be more of a factor than it would be with a tube
> > > filled with oil alone.
> > >
> >
> > Air is compressible. Oil is not. Air in the line will result in a
falsely
> > low gauge reading. At least that's what happened to me many years ago
when
> > I added such a device to my car.
>
> How did you make the leap from air is compressible to it will result in
> a falsely low gauge reading? You say that as if everyone is supposed to
> automagically see the connection.
>
> -jim


As his previous posts and replies have conclusively proven,
he wouldn't pass a first year class in statics. Gawd forbid his
next attempt to pointificate on the Navier-Stokes equations.

Ray O > wrote:
>
>The downside to using a direct read gauge is that there are additional
>potential sources of oil leaks, and leaking hot oil in the instrument panel
>can cause burns and make a huge mess.

The MG manual says that it isn't a leak, it's just "normal seepage."
--scott
>


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Tegger" > wrote in message
...
> "hls" > wrote in
> :
>
>>
>> "dr_jeff" > wrote in message
>>> Why would having the oil go all the way up to the gauge be a big
>>> deal? Would there always be oil in the line?
>>
>> It wouldnt normally make much difference. If the line, partially
>> filled with air,
>> experienced heating or cooling, I guess the expansion or contraction
>> of the air could be more of a factor than it would be with a tube
>> filled with oil alone.
>>
>
>
> Air is compressible. Oil is not. Air in the line will result in a falsely
> low gauge reading. At least that's what happened to me many years ago when
> I added such a device to my car.
>
> --
> Tegger

The pressure is transmitted through the "fluid", both air and oil being
fluids. You dont lose
pressure just because the air is compressed.

"Ray O" > wrote in message
...
>
> "muzician21" > wrote in message
> ...
>> Hooking up an oil pressure gauge, should the oil go all the way to the
>> gauge or should there be an air buffer?
>>
>> Thanks
>
> Are you hooking up the gauge temporarily to check oil pressure or are you
> trying for a permanent installation in the dashboard?
>
> In either case, the oil needs to go all the way to the gauge unless you
> are using an electrical sender type gauge.
>

What Ray said. And IF it's an electrical guage, the sender will be screwed
directly into an oil galley somewhere, and the wire will go all of the way
to the guage.




> The downside to using a direct read gauge is that there are additional
> potential sources of oil leaks, and leaking hot oil in the instrument
> panel can cause burns and make a huge mess.

That's an understatement ...

"dr_jeff" > wrote in message
...
> Ray O wrote:
>> "muzician21" > wrote in message
>> ...
>>> Hooking up an oil pressure gauge, should the oil go all the way to the
>>> gauge or should there be an air buffer?
>>>
>>> Thanks
>>
>> Are you hooking up the gauge temporarily to check oil pressure or are you
>> trying for a permanent installation in the dashboard?
>>
>> In either case, the oil needs to go all the way to the gauge unless you
>> are using an electrical sender type gauge.
>>
>> The downside to using a direct read gauge is that there are additional
>> potential sources of oil leaks, and leaking hot oil in the instrument
>> panel can cause burns and make a huge mess.
>
> Why would having the oil go all the way up to the gauge be a big deal?
> Would there always be oil in the line?


Of course there's oil in the line. How else would oil pressure be measured
without oil in the line measuring the pressure?

>The pressure is transmitted through the "fluid", both air and oil being
>fluids. You dont lose
>pressure just because the air is compressed.

You wouldn't lose static pressure but the air would buffer transients.
So air in the line is not necessarily a bad thing.

"dr_jeff" > wrote in message
...
> Ray O wrote:
>> "muzician21" > wrote in message
>> ...
>>> Hooking up an oil pressure gauge, should the oil go all the way to the
>>> gauge or should there be an air buffer?
>>>
>>> Thanks
>>
>> Are you hooking up the gauge temporarily to check oil pressure or are you
>> trying for a permanent installation in the dashboard?
>>
>> In either case, the oil needs to go all the way to the gauge unless you
>> are using an electrical sender type gauge.
>>
>> The downside to using a direct read gauge is that there are additional
>> potential sources of oil leaks, and leaking hot oil in the instrument
>> panel can cause burns and make a huge mess.
>
> Why would having the oil go all the way up to the gauge be a big deal?
> Would there always be oil in the line?

Oil going all the way to the gauge is only a big deal if the gauge is
mounted in the passenger compartment or instrument panel and it leaks and
causes burns or worse, catches fire. I suppose another downside to having
an oil line in the passenger compartment is that the oil line would radiate
some heat from hot oil into the passenger compartment - not a big deal in
the winter, but annoying in hot weather.

Whether or not there would always be oil in the line depends on how the line
is installed but most likely, oil would drain out when the engine is shut
down.

I got the impression that the OP was installing an oil pressure gauge to
diagnose an oil pressure warning light, so the installation was temporary
and not a permanent instrument panel installation, making most of this
thread a moot point.
--

Ray O
(correct punctuation to reply)

Ray O > wrote:
>Oil going all the way to the gauge is only a big deal if the gauge is
>mounted in the passenger compartment or instrument panel and it leaks and
>causes burns or worse, catches fire.

This is traditional British design, and indeed in MGs it does all of the
above. It's part of the charm of the vehicles, much like switching the
current to the headlights directly through an undersized switch on the
dash rather than with a relay.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" > wrote in message
...
> Ray O > wrote:
>>Oil going all the way to the gauge is only a big deal if the gauge is
>>mounted in the passenger compartment or instrument panel and it leaks and
>>causes burns or worse, catches fire.
>
> This is traditional British design, and indeed in MGs it does all of the
> above. It's part of the charm of the vehicles, much like switching the
> current to the headlights directly through an undersized switch on the
> dash rather than with a relay.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

Add the fun of truing spoke wheels and non synchromesh transmission...

--

Ray O
(correct punctuation to reply)