Should oil in pressure line for gauge go all the way to the gauge?
muzician21
gauge or should there be an air buffer?
Thanks
Tegger
90aa95...@c3g2000yqd.googlegroups.com:
> Hooking up an oil pressure gauge,
Huh. Useless and dicey aftermarket gauge.
> should the oil go all the way to the
> gauge or should there be an air buffer?
>
ALL the way! /Any/ air is unacceptable.
--
Tegger
C. E. White
"muzician21" <muzic...@yahoo.com> wrote in message
news:73fba85d-edcd-4d8e...@c3g2000yqd.googlegroups.com...
> Hooking up an oil pressure gauge, should the oil go all the way to the
> gauge or should there be an air buffer?
>
> Thanks
It shouldn't matter.If there is air in the line, it will be compressed so
that the "air" pressure is the same as the oil pressure.
I don't really like gauges that require running oil lines to the
dash -especially the sort sold in most mass market auto parts stores. I
prefer good quality electical gauges.
Ed
muzician21
coming on when hot and at low idle, about 30 - 40k out from a rebuild.
Oil sender was replaced new when the engine was built.
Gauge from Advance which I realize you're going to turn up your nose
at is showing really low - like about 5 psi at about 600 - 700 rpm.
Jumps up well over 30 psi at highway speed.
I've always heard 10psi per 1000 rpm as a ROT, seem to be getting
enough pressure at speed but seems low at idle. Am probably going to
change the pump out and see if that cures it. Got a Clevite pump,
anyone have any feelings about them one way or the other?
Thanks
Ray O
"muzician21" <muzic...@yahoo.com> wrote in message
news:73fba85d-edcd-4d8e...@c3g2000yqd.googlegroups.com...
> 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.
--
Ray O
(correct punctuation to reply)
Ray O
The factory repair manual has specs for clearances between the crescent,
impeller, and pump body. Check the clearances before you swap the pump.
Besides a bad pump, excessive bearing clearances can cause low oil pressure.
dr_jeff
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?
hls
"dr_jeff" <u...@msu.edu> 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.
Tegger
news:n7OdneWHlYElMqHW...@giganews.com:
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
jim
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
Kevin
news:qqWdnS6fv-RgJ6HW...@bright.net:
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
The 2nd Admendment guarantees the others
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Heron McKeister
news:qqWdnS6fv-RgJ6HW...@bright.net...
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.
Scott Dorsey
>
>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."
hls
"Tegger" <inv...@invalid.inv> wrote in message
news:Xns9CF26359...@208.90.168.18...
The pressure is transmitted through the "fluid", both air and oil being
fluids. You dont lose
pressure just because the air is compressed.
Jeff Strickland
"Ray O" <roki...@NOSPAMtristarassociates.com> wrote in message
news:hhhauh$9ub$3...@news.eternal-september.org...
>
> "muzician21" <muzic...@yahoo.com> wrote in message
> news:73fba85d-edcd-4d8e...@c3g2000yqd.googlegroups.com...
>> 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 ...
Jeff Strickland
Of course there's oil in the line. How else would oil pressure be measured
without oil in the line measuring the pressure?
tn...@mucks.net
>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.
Ray O
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.
Scott Dorsey
>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.
Ray O
"Scott Dorsey" <klu...@panix.com> wrote in message
news:hhiugs$lop$1...@panix2.panix.com...
Add the fun of truing spoke wheels and non synchromesh transmission...
Vic Smith
wrote:
>
> 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.
>
It will be "falsely low" - momentarily.
This guy did a useful test of bled line versus non-bled.
http://mgaguru.com/mgtech/dash/dt104.htm
There are other examples if you care to find them.
In any case, I'd just go with an electric.
The one in my Grand Am seems responsive enough.
Interesting comment in the last paragraph about possible false
indication of oil filter drain down.
No, I'm not suggesting another Fram thread.
--Vic
FatterDumber& Happier Moe
You could put a direct reading gauge on the engine with a light and
camera focused on it and a video screen with a big suction cup on it to
stick on the windshield. Or maybe an air gauge attached to the oil
line to measure the air pressure and compare it to the oil
pressure...... with two big suction cups to hold them, and of course a
vacuum gauge to measure the suction on the suction cups so you will know
when they are about to fall off, which would require another two gauges
and more suction cups unless they have a remote sensor.....
Vic Smith
<"WheresMyCheck"@UncleSamLoves.Mee> wrote:
>
> You could put a direct reading gauge on the engine with a light and
>camera focused on it and a video screen with a big suction cup on it to
>stick on the windshield. Or maybe an air gauge attached to the oil
>line to measure the air pressure and compare it to the oil
>pressure...... with two big suction cups to hold them, and of course a
>vacuum gauge to measure the suction on the suction cups so you will know
>when they are about to fall off, which would require another two gauges
> and more suction cups unless they have a remote sensor.....
Too complicated and expensive. Just lead an oil hose to a covered
bucket kept on the passenger seat. Another hose on the side of the
bucket near the bottom goes back to the engine.
Then you stick a meat thermometer through the cover, and a dipstick.
After a little testing to get the return hose sized right and the
temperature/bucket level calibrated right, it just a question of
checking the dipstick. Could put a sight glass on it if you like
fancy.
Anyway, you won't need a TV on the windshield then.
--Vic
Tegger
news:Ph3%m.5533$0U1...@newsfe16.iad:
> "jim" <"sjedgingN0Sp"@m@mwt,net> wrote in message
> news:qqWdnS6fv-RgJ6HW...@bright.net...
>>
>>
>> Tegger wrote:
>> >
>> > >
>> >
>> > 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.
>>
>>
>
>
> 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.
>
>
>
Firstly, I'd like to thank all for their friendly and good-natured replies
to my posts.
Secondly, here's the explanation:
Way, way back in the early '80s, I installed a capillary-type Auto Meter
oil pressure gauge in my '75 Corolla. There was air in the line after I
hooked it up. The gauge barely read anythng at all. I decided that the
problem was probably the air, so I made sure I bled out as much as I could
before reconnecting the line. The gauge then displayed a more normal
reading.
If the air didn't matter, then I obviously inadvertently did something else
that fixed the low reading, but mistakenly attibuted the fix to the removal
of the air.
--
Tegger
Tegger
news:JOmdneSwssLqQqHW...@giganews.com:
So I've been believing a misconception these last 28 years. You, at least,
was civil in pointing this out to me.
--
Tegger
FatterDumber& Happier Moe
pumping 45lbs/square inch or whatever it is at the pump outlet that
would be 45 lbs/sq inch at the gauge. Air or no air. Any air in the
line would be compressed to 45Lbs and that's what the gauge would read.
OK that's it, this is the correct answer, I should know I made a
strong D- in physics.
Thread closed.
jim
Vic Smith wrote:
>
> On Thu, 31 Dec 2009 08:53:46 -0600, jim <"sjedgingN0Sp"@m@mwt,net>
> wrote:
>
> >
> > 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.
> >
> It will be "falsely low" - momentarily.
> This guy did a useful test of bled line versus non-bled.
> http://mgaguru.com/mgtech/dash/dt104.htm
It would have been more useful if it was done with more conventional oil - He
said he was doing the test with cold 20w50 oil. With 5w30 oil I would guess the
difference between air in the tube and no air would be much less noticeable.
The size of the tubing and thickness of the oil will determine how fast the
gauge responds.
Also, after the air is bled from the tube there shouldn't be any way the oil
can drain back out of the tube. If it does that probably means a tiny leak that
is too small for oil to leak out but big enough for air to leak in.
>
> There are other examples if you care to find them.
> In any case, I'd just go with an electric.
The electric gauge/sensor will have some dampening also to protect the gauge
from damage. Depending on how it is set up it could also have some small delay.
-jim
FatterDumber& Happier Moe
good as a genuine Toyota Filter.
Tegger
news:4b3d1394$0$5343$bbae...@news.suddenlink.net:
> Tegger wrote:
>>
>> Secondly, here's the explanation:
>> Way, way back in the early '80s, I installed a capillary-type Auto
>> Meter oil pressure gauge in my '75 Corolla. There was air in the line
>> after I hooked it up. The gauge barely read anythng at all. I decided
>> that the problem was probably the air, so I made sure I bled out as
>> much as I could before reconnecting the line. The gauge then
>> displayed a more normal reading.
>>
>> If the air didn't matter, then I obviously inadvertently did
>> something else that fixed the low reading, but mistakenly attibuted
>> the fix to the removal of the air.
>>
>>
>>
> Unless there is a blockage somewhere in the line when the pump is
> pumping 45lbs/square inch or whatever it is at the pump outlet that
> would be 45 lbs/sq inch at the gauge. Air or no air. Any air in the
> line would be compressed to 45Lbs and that's what the gauge would
> read.
> OK that's it, this is the correct answer, I should know I made a
> strong D- in physics.
> Thread closed.
<opens thread again>
That makes perfect sense, now that I've actually given this some thought.
Makes me wonder what I did wrong those 28 years ago.
<gently closes the thread once more>
--
Tegger
Nate Nagel
small amount of debris in the line that plugged the little hole on the
back of the gauge, that got blown out when you bled the line?
I dunno, that's the best I can come up with on short notice
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
hls
"Tegger" <inv...@invalid.inv> wrote in message
>
> was civil in pointing this out to me.
>
>
> --
> Tegger
I must be slipping, Teg.
The oil will flow up the line until the pressure of the
oil and the pressure of the air will equilibrate.. But there is a BUT...If
the
small amount of air in that line is heated substantially, it will expand
and/or the
pressure will increase, more or less as predicted by the universal gas law.
This
pressure can add to the pressure provided by the oil system, and you may see
an increase. In going from ambient of about 100F to 250C, this would not
provide a pressure error of more than 20-25%, or - if you were looking for
a true oil pressure of 30 psi - about 6-7 psi. A lot of cheapo gauges are
not
much better than that.
hls
"Ray O" <roki...@NOSPAMtristarassociates.com> wrote in message news:hhivh7
>> 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."
And the electrical components and systems created by the "Lords of
Darkness", Lucas
Tegger
news:JP6dnYiPY98RtqDW...@giganews.com:
Well, I never took physics, so this is all somewhat Greek-ish to me.
If the air in the line were to expand due to heat, wouldn't it simply push
back on the column of oil being pushed up from the engine?
I can understand that pressure would rise with heat-induced gas expansion
in a sealed system, but the oil pressure gauge isn't a sealed system, is
it?
--
Tegger
aarcuda69062
"hls" <h...@nospam.nix> wrote:
Any increased pressure in the line from heating of the air trapped in it
would simply become an opposing force to the oil pressure from the pump
and would dissipate back into the oiling system.
Pressure can not exceed what the regulated pressure is to begin with.
This whole thing is a non-issue.
Heron McKeister
news:JP6dnYiPY98RtqDW...@giganews.com...
I must most strenuously disagree. Absent any valving or
a significant flow rate, the pressure in a hydraulic system
is essential the same everywhere.
Jeff Strickland
"FatterDumber& Happier Moe" <"WheresMyCheck"@UncleSamLoves.Mee> wrote in
Yeah, you could do that. Maybe there's an app for that ...
Jeff Strickland
"Ray O" <roki...@NOSPAMtristarassociates.com> wrote in message
The oil would only drain to the extent that air could enter the line,
otherwise the vacuum and surface tension would hold the oil in place. If the
system was sealed properly (a very big IF in this case), then the oil ought
not drain from the hose leading to the guage. Small hose, thick oil, sealed
end on the hose. The oil should remain in place.
hls
"Tegger" <inv...@invalid.inv> wrote in message
>
>
>
> If the air in the line were to expand due to heat, wouldn't it simply push
> back on the column of oil being pushed up from the engine?
>
> I can understand that pressure would rise with heat-induced gas expansion
> in a sealed system, but the oil pressure gauge isn't a sealed system, is
> it?
>
>
> --
> Tegger
And the answer is yes. The unusual pressure due to the air would push
backwards
against the oil pressure. Here is where it becomes dicey.. The amount of
air in
the line is small. So even if it expands, its expansion is limited by its
volume,
or weight, as a part of the system.
The differences are usually much smaller than the case I related to you.
hls
"aarcuda69062" <none...@sbcglobal.net> wrote in message
news:nonelson-79D1B5...@news.eternal-september.org...
That is what I had hoped to get across, but on this thread if you make a
small
approximation, someone will come to take your hide.
Mike Hunter
"hls" <h...@nospam.nix> wrote in message
news:y_adnRwozq4IfKLW...@giganews.com...
Heron McKeister
from my first semester thermodynamics professor (Dr.
Izawa), that some liquids can be relatively compressible,
namely both ethane and carbon dioxide.
"Mike Hunter" <Mikehunt2@lycos,com> wrote in message
news:4b40d6c1$0$20778$ce5e...@news-radius.ptd.net...
dr_jeff
> In general, true. However I recall hearing for the first time,
> from my first semester thermodynamics professor (Dr.
> Izawa), that some liquids can be relatively compressible,
Liquid helium is compressable, too, IIRC. You need to get down to around
4 K (about -255 C or -450 F) to get liquid helium.
Jeff
Heron McKeister
behaviors.as well. Despite how it may have come across
though, I hadn't actually meant the examples I mentioned
as being a comprehensive listing ;^)
"dr_jeff" <u...@msu.edu> wrote in message
news:beidnSV1y76GQt3W...@giganews.com...
hls
> 4 K (about -255 C or -450 F) to get liquid helium.
>
> Jeff
It is a matter of degree. Liquids have very very low compressabilities.
You would not be able to measure the compressability of motor oil
on a simple automotive oil gauge.
Put it under several hundred or several thousands of atmospheres, then
you could measure it with a very sensitive instrument.
It is not even a factor in this general discussion.
hls
"hls" <h...@nospam.nix> wrote in message
http://www.engineersedge.com/lubrication/compressibility_hydraulic_fluid.htm.
Here is a link with some approximate information.
Mike Hunter
;)
"dr_jeff" <u...@msu.edu> wrote in message
news:beidnSV1y76GQt3W...@giganews.com...
Steve
>
> "muzician21" <muzic...@yahoo.com> wrote in message
> news:73fba85d-edcd-4d8e...@c3g2000yqd.googlegroups.com...
>> Hooking up an oil pressure gauge, should the oil go all the way to the
>> gauge or should there be an air buffer?
>>
>> Thanks
>
> so that the "air" pressure is the same as the oil pressure.
>
> I don't really like gauges that require running oil lines to the dash
> -especially the sort sold in most mass market auto parts stores. I
> prefer good quality electical gauges.
>
> Ed
My experience is that electric gauges are awful. Very inaccurate, though
not as completely useless as factory gauges. Even fairly cheap
mechanical gauges are much more accurate.
Go to a high-performance shop and get COPPER capillary tubing if you're
worried about the hard nylon tubing that comes with gauges. Although
I've never had the hard nylon stuff fail either- but you do have to
route it carefully to avoid abrasion or getting it against something too
hot.
Steve
>
> It wouldnt normally make much difference.
That's the correct answer. It doesn't really make much difference.
Having a little air in the line does help smooth out pulsations in oil
pressure (from the pump, from the crank and camshafts alternately
covering and uncovering various passages.) Air in the line does not
decrease accuracy.
Steve
> "hls" <h...@nospam.nix> wrote in
>> "dr_jeff" <u...@msu.edu> 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?
>> 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.
>>
>
>
> low gauge reading.
Ummm... no.
The air compresses to the exact same pressure as the oil in the engine
and the gauge reads correctly.
hls
"Steve" <n...@spam.thanks> wrote in message
news:C6SdnQoROYq4QdHW...@texas.net...
Double ditto...I have seen MANY times that people route these nylon lines
too close to a heat source and they eventually melt or decompose. If you
do it properly, nylon is a good material, but this is no place to get
sloppy.