1994 xj6 3.2s with 129,000
i have a problem with oil pressure when car is warm where as it
drops at idle then picks up well (in the middle of gauge) when
moving… Is this a worry or normal?? should I be careful or not
drive it at all???
would appreciate any advice…thanks–
phippsy
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1994 xj6 3.2s with 129,000
i have a problem with oil pressure when car is warm where as it
drops at idle then picks up well (in the middle of gauge) when
moving… Is this a worry or normal?? should I be careful or not
drive it at all???
would appreciate any advice…thanks
I take it you have checked your oil level, and you change the oil
regularly. If you are not seing any other problems, the chances are that
it is a dodgy oil pressure sensor. You could get a capilary gauge to
check what the real reading is. All of my XJ40s read at least
3+bar/50+psi at idle and 7+bar/80+psi (usually off scale) above 2000rpm
when hot.
If you haven’t done it before, I’d recommend putting some oil flush
through the system at the next oil change. It clears out all the sludge
from the system, and I have seen the pressure increase by 15+psi on cars
that haven’t been flushed regularly.
But it’s most likely a dodgy pressure sensor. They are known to go
wrong. If that is the case and you decide to replace it, make sure you
get the old type sensor that actually gives you a reading, rather than
just being a glorified idiot light that reads full or nothing.
Gordan
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Oil pressure will rise and fall with engine RPM.
That is normal to a degree especially at hot temperatures.
The oil pressure sending units are also not the most reliable so its
possible the sender is starting to give up.----- Original Message -----
From: “phippsy” willphipps@hotmail.com
To: xj40@jag-lovers.org
Sent: Thursday, February 17, 2005 6:42 AM
Subject: [xj40] oil pressure readings!!!
1994 xj6 3.2s with 129,000
i have a problem with oil pressure when car is warm where as it
drops at idle then picks up well (in the middle of gauge) when
moving… Is this a worry or normal?? should I be careful or not
drive it at all???
would appreciate any advice…thanks
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !
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In reply to a message from Gordan Bobic sent Thu 17 Feb 2005:
Gordan - what type of oil flush do you use/recommend and how does
it work? I might try it when I get my oil changed in the next month
or so. Its either that or get the idiot light.
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In reply to a message from Gordan Bobic sent Thu 17 Feb 2005:
Gordan - what type of oil flush do you use/recommend and how does
it work?
I personally use the Forte (NAYYY) engine flush (Google for it). You put
in one (or preferrably two on an AJ6 engine, 3 in the V12) bottles of
the stuff into the oil before you change it. Run the car at fast idle
for 20-30 minutes. Then change the oil and filter as per normal. That’s it.
It works for me. YMMV.
I might try it when I get my oil changed in the next month
or so. Its either that or get the idiot light.
It’s worth checking if your oil pressure really is too low or whether
you just have a duff sensor. If it’s just the sensor, it’s worth
replacing it, if only for the peace of mind.
Also note that two bottles of the engine flush I mentioned are likely to
cost you more than the new sensor. But then again, the fully synthetic
oil will cost you about twice that again…
Gordan
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According to the drivers manual [assuming you have the gage that
actually reads pressure in kPa] if you have 2.3 reading on the gage [230
kpa] at 2000 RPM you have adequate oil pressure. The only way you will
know is to hook up a pressure gage to the oil line [see archives].
First thing is to determine if you actually have an actual analog
pressure sender and not the sender that is nothing more than an idiot
light, see the archives fro details…
And of course its normal for the pressure to drop on idle and go up to
4.7 on the gage when running. So long as the gage does not go in the
red zone it would be assumed to be OK.
Also you don’t note the oil weight or grade being used. If you use
10/30w oil you will have slightly less pressure top end and a lot less
pressure low end when the oil is hot than if you use 10/50w [good to
Hudson’s Bay latitude] or 20/50w Castrol GTX [good year round most US
locations].
Its unlikely the oil pump will ever fail as it is a lobe type with no
friction contact [two wheels spin in an oil bath] so it will probably
last forever unless some unusual circumstance occurs. It will even run
dry for quite a bit until the oil in the bearings leaks out.
Cheers
Jay 90 VDP Majestic
phippsy wrote:
1994 xj6 3.2s with 129,000
i have a problem with oil pressure when car is warm where as it
drops at idle then picks up well (in the middle of gauge) when
moving… Is this a worry or normal?? should I be careful or not
drive it at all???
would appreciate any advice…thanks
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Wow that is amazing [your pressure readings that is]
I have owned Jags for 22 years and never seen one that read 7 on the
gage [700 kPa] when hot or cold for that matter and I use 20/50w year
round. If you have reading o 7 or 8 kPa when hot above 2000 RPM, I
would check the gage out as it is unlikely to be accurate.
The gage is graduated in kilo pascals x 100 [the number on the gage x
100 = the kPa]. try http:\www.sonic.om\uselfulinfo_onvert.stm for the
actual conversion data and owners manual page 50 for information on the
gage calibration in kPa.
A kilo pascal = 0.145 psig so 470 kPa = 68.15 psig which is more than
adequate oil pressure for most cars at operating speed. At 700 kPa it
would be 101.5 psig
For comparison a Bar = 14.504 psig and the actual pressure in PSIG will
be about the same [68.388] if you multiply the number on the gage
[disregarding the fact that it is a number x 100 = kPa]. However, the
owners manual says the gage is a number x 100 so don’t make the mistake
of multiplying the number x 100 x bars as that will be 100 times too
high. Don’t ask me why Jaguar used kPa and put a note in the manual to
multiply the gage reading x 100.
According to the shop owners manual, [I stand corrected from my previous
post which said 230 kPa at 2000 RPM was the minimum pressure for proper
engine operation]. The correct figure is 275 kPa [2.75 on the gage x
100] at 3000 RPM’s on a warm engine. That comes to about 38 psig as the
minimum pressure required at speed on a warm engine.
From experience 4.7 - 5.0 on the gage [470 kilo pascals] is the normal
pressure when running at 2000 - 3000 RPM on a hot engine in my car and
has been that way since 1994.
My oil pressure reading taken from a gage installed on the system pretty
much agrees with the dash gage reading so I am confident the gage
reading is correct
Jay 90 VDP Majestic
Gordan Bobic wrote:
I take it you have checked your oil level, and you change the oil
regularly. If you are not seing any other problems, the chances are
that it is a dodgy oil pressure sensor. You could get a capilary gauge
to check what the real reading is. All of my XJ40s read at least
3+bar/50+psi at idle and 7+bar/80+psi (usually off scale) above
2000rpm when hot.
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In reply to a message from phippsy sent Thu 17 Feb 2005:
I had the same problem. The guys in my workshop disconnected the
cable from the oil pressure sender (front of left side of engine)
and put some volts on the cable to check the gauge. It was OK so
they pronounced the sender faulty. Having done this it is OK to
drive the car, assuming it isn’t making any bad noises.
After they fitted a new sender the oil pressure was normal, 3KPa at
idling (warm) and 4+ when above 1000rpm.
In the driver’s manual it says the OP should not be below 2.85(!)
at 3,000rpm.–
PhoneyDick
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In reply to a message from PhoneyDick sent Mon 7 Mar 2005:
My oil pressure guage started doing the same thing in my 89 XJ6,
it would just suddenly drop to zero for about 15 seconds and they
jump real high. Back and forth all the time while driving.
Replaced, it has been fine ever since.
Good Luck!
Patrick–
The original message included these comments:
In reply to a message from phippsy sent Thu 17 Feb 2005:
I had the same problem. The guys in my workshop disconnected the
cable from the oil pressure sender (front of left side of engine)
and put some volts on the cable to check the gauge. It was OK so
they pronounced the sender faulty. Having done this it is OK to
drive the car, assuming it isn’t making any bad noises.
After they fitted a new sender the oil pressure was normal, 3KPa at
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In reply to a message from PhoneyDick sent Mon 7 Mar 2005:
thanks for the advise… I ll get it checked out… does seem
rather low the ‘min rading’ as suggested in the manual, and at high
revs!!!–
phippsy
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Just Curious. What did you replace, the sender or the gage. If you
replaced the sender did no you replace it with the idiot light sender or
were you able to get one of the older analog reading sender units that I
have been lead to believe are no longer available? Just curious as I
want to buy a spare of the real reporting type sender before mine wears
out and avoid being stuck with the idiot light sender unit.
Jay 90 VDP Majestic
bigdog7708 wrote:
In reply to a message from PhoneyDick sent Mon 7 Mar 2005:
My oil pressure guage started doing the same thing in my 89 XJ6,
it would just suddenly drop to zero for about 15 seconds and they
jump real high. Back and forth all the time while driving.
Replaced, it has been fine ever since.
Good Luck!
Patrick
The original message included these comments:
In reply to a message from phippsy sent Thu 17 Feb 2005:
I had the same problem. The guys in my workshop disconnected the
cable from the oil pressure sender (front of left side of engine)
and put some volts on the cable to check the gauge. It was OK so
they pronounced the sender faulty. Having done this it is OK to
drive the car, assuming it isn’t making any bad noises.
After they fitted a new sender the oil pressure was normal, 3KPa at
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Just Curious. What did you replace, the sender or the gage. If you
replaced the sender did no you replace it with the idiot light sender or
were you able to get one of the older analog reading sender units that I
have been lead to believe are no longer available? Just curious as I
want to buy a spare of the real reporting type sender before mine wears
out and avoid being stuck with the idiot light sender unit.
Jay 90 VDP Majestic
bigdog7708 wrote:
In reply to a message from PhoneyDick sent Mon 7 Mar 2005:
My oil pressure guage started doing the same thing in my 89 XJ6,
it would just suddenly drop to zero for about 15 seconds and they
jump real high. Back and forth all the time while driving.
Replaced, it has been fine ever since.
Good Luck!
Patrick
The original message included these comments:
In reply to a message from phippsy sent Thu 17 Feb 2005:
I had the same problem. The guys in my workshop disconnected the
cable from the oil pressure sender (front of left side of engine)
and put some volts on the cable to check the gauge. It was OK so
they pronounced the sender faulty. Having done this it is OK to
drive the car, assuming it isn’t making any bad noises.
After they fitted a new sender the oil pressure was normal, 3KPa at
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !> To: bigdog7708 bigdog7708@aol.com
In reply to a message from Jay sent Mon 7 Mar 2005:
Mine was not the idiot light type, I got it used off of EBAY. It
was not a new unit, but in good working condiontion.–
The original message included these comments:
Just Curious. What did you replace, the sender or the gage. If you
replaced the sender did no you replace it with the idiot light sender or
were you able to get one of the older analog reading sender units that I
have been lead to believe are no longer available? Just curious as I
want to buy a spare of the real reporting type sender before mine wears
out and avoid being stuck with the idiot light sender unit.
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I seems that I’m not the only one that are confused over the reading of the oil pressure gauge. The scale of the gauge in my XJ40 4.0S -94 is from 0-8 bar (= x100 kPa) where 4 is straight up. When starting the car cold, the gauge always reads 4. When engine is hot, the pressure falls which i guess is normal. What worries me is that it falls below 2 in idling speed at 600 rpm. And it might also happen that it falls close to 1 which makes the red oil pressure warning light to light up. But when giving more throttle, the pressure comes up.
So my question is just to you people who have a similar cars. -What oil pressure do you read of the meter at idling speed when engine is warm ? (I have not found this in any manual)
I have seen in the tread that there have been problems with the sensors. But if this would have been a sensor problem, I believe it not would have affected booth the meter and the warning light since I would assume there are different sensors for the gauge and the red light alarm. But mabee these signals come from the same sensor ?
Any thoughts on this would be appreciated. The car runs well.
Bottom line is if I need to worry or not. (I do regular oilexchange)
My oil pressure gage has done the exact same thing for the last six years-dropping close to zero when warm. It is definately the sensor and one of these days I’ll change it. I have the car running so well at this time, I’m afraid if I fix the sensor I’ll curse myself. These cars don’t seem to want to leave us without any quirks!
They all do this eventually. I replaced mine with an aftermarket unit from Beck Arnley part#2011505 and in order to agree with the XJ40 gauge calibration, I made up and fitted a 75 Ohm resistor between the unit and the harness.
Problem solved. BTW - if you access the oil pressure gauge from below, on the 94 you need to remove the oil cooler bypass to get reasonable access, so a good time to replace the o-rings in there at the same time.
Here’s a pic of the resistor, it’s just two connectors with the 75ohm resistor between and a coat of shrink tubing.
Larry,
Thanks again for a useful tip. I found the picture of the sensor at the Beck Arnley web. So now I know what to look for in the engine room.
Have you, or anyone, any ideas why this sensor don’t seem to survive ?
Have anyone tried to repair/clean/take apart the original sensor?.
Pressure sensors in general often consists of a membrane with the liquid on one side and the electronics on the other side in a sealed chamber. What I could think of is that it either is a whole in the membrane or that the liquid-side just is filled up with 20+ year old oil that prevent the membrane from being as flexible as it should. But if so, then I believe it should work better when hot than cold which not is the case.
But since the pressure drops when it gets hot It maybe could be a very small hole in the membrane. Or between the membrane and the wall of the chamber. So small that the oil can’t pass when it is cold/thick which makes the membrane to move and present reading (more or less correct). But when hot, the oil passes though to the other side which results in no difference in pressure on the two sides of the membrane and a 0 reading. But it would then be oil in the electronics and if so it would probably not present ant values at all…
So, how about it the membrane is OK but that the sensors leaks air on the electronic side when it gets hot. For example around the cable connector outlet which probably is made of some insulating plastic. And 20 year old plastic that vibrates could fall apart. I have also seen simple oil pressure switched on other cars where the insulator plastic have become old causing the oil to spray the engine room and loss of pressure.
If that is the case, it might be able to repair it with some epoxy glue around the cable connector… After all all we are only dealing with pressure in the range of up to max 8 bar.
I will probably give this a try. If no one here have any better idea. This sensor must be pretty easy to check on the bench with an ordinary aircompressor simulating the oil pressure. At least when it is cold. Otherwise it cant be that difficult to heat it up buy putting it in warm water.
Nothing too complex Patrik, I think the little hole just gets clogged up! …some people think it’s the heat that fries them …AFAIK the same sensor is used in the earlier XJ’s and because of the position (so I’m told) they don’t fail like the XJ40 units do.
I believe there is a GM sender that works and reads in actual pressure. Many GM small trucks had a dash gauge that read in actual pressure. Some time after Jaguar Cars was bought by Ford they found the easy (cheap) way out of warranty costs was to fit a Ford type sender that only made the gauge read in the middle of the scale all the time. Drive a late 1990s Ford Crown Victoria and you will see this type operation. Many owners of the in warranty cars were not happy when their gauge was converted to the on/off reading. The apparent issue with the variable senders is that the coil inside would wear out as the “finger” ran over it continuously as oil pressure varied.
AFAIK, the Ford type sender you refer to was fitted beginning with the X300 in late 1994.
All XJ40’s had real gauges and yes, some of them crapped out and were replaced with the idiot light type, my own parts car had that setup.
Most of the guys I know with 40’s prefer the “actual” pressure readings and after much experimentation getting the aftermarket units to agree with the dash gauge correctly, Jim Goodwin of Nanaimo BC measured the pressure and determined the correct value for the in-line resistor (75 ohm).
Prior to Jim figuring it all out (about 2 years ago) the guesstimated resistor bandied about on the forums was 150 ohm, but that value makes the gauge read way too low.
Now there’s no need for a 40 owner to drive around with zero pressure readings or with a mid-point on-off idiot switch. We can all just get an aftermarket unit, fit the 75 ohm resistor and have the system work as intended. Thanks Jim!
Thanks Jim!