After a full repair of the engine of my MK10, done by
myself, I have had a disagreable surprise. Oil pressure was
a bit low. With a SAE 30 oil, pressure reaches only 30 psi
at 3000 rpm, with the motor hot. Suspecting a possible
problem I install a mechanical dial pressure gauge in the
presurre sender place and I obtained then more tan 40 psi
at 3000 rpm. So the engine is OK and the sender or the dial
gauge are in bad condition. The voltage regulator for the
instruments works well, so the problem is in the sender or
in the dial gauge. Can anyone suggest me how can I discern
where is the problem ? Furthermore it is posible to readjust
the dial gauge ?.
Thanks in Advance,
Creuse–
JSR
sant jordi, 23 08757 Corbera, Spain
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In reply to a message from creuse sent Wed 13 Feb 2013:
No absolute certainty but usually the sending unit is the
faulty item. A new sending unit will probably fix the reading.–
The original message included these comments:
problem I install a mechanical dial pressure gauge in the
presurre sender place and I obtained then more tan 40 psi
at 3000 rpm. So the engine is OK and the sender or the dial
The gauges are theoretically adjustable. Drop down the instrument panel and
you will see two holes in the back of the gauge which were originally (and
could still be) plugged with cork. Inside the holes are screwdriver slots
which can be twisted ever so slightly to adjust the reading. The one on the
left (as you see it with the panel down) adjusts the zero position and the
one on the right adjusts the range. They interact so you may need to go
back and forth between them to get the gauge to read zero when there is no
pressure and read correctly when there is. Put the panel in the upright
position when checking it because the gauges read differently when lying
down.
Here’s why I said “theoretical”. I had EXACTLY the same problem as you in
that my gauge read 30 when it should have read 40. I could have ignored it
but I thought I would feel better with the correct reading. However, I
discovered that my adjustments would not move. On the back of the gauge you
will also see two rivets, which are the pivot points for the things inside
that you are trying to adjust. My rivets were absolutely tight and no
amount of persuasion would make them turn loose. I ended up doing major
internal gauge surgery to get it to read properly. If you find that to be
the case I would recommend you try some other solution, such as trying
another sender or simply knowing that when your gauge reads 30 it really
means 40.
After a full repair of the engine of my MK10, done by
myself, I have had a disagreable surprise. Oil pressure was
a bit low. With a SAE 30 oil, pressure reaches only 30 psi
at 3000 rpm, with the motor hot. Suspecting a possible
problem I install a mechanical dial pressure gauge in the
presurre sender place and I obtained then more tan 40 psi
at 3000 rpm. So the engine is OK and the sender or the dial
gauge are in bad condition. The voltage regulator for the
instruments works well, so the problem is in the sender or
in the dial gauge. Can anyone suggest me how can I discern
where is the problem ? Furthermore it is posible to readjust
the dial gauge ?.
Thanks in Advance,
Creuse
JSR
sant jordi, 23 08757 Corbera, Spain
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In reply to a message from Mike Eck sent Wed 13 Feb 2013:
I have previously swapped senders, which did not alter my
readings, which were max 25psi, and alarmingly close to 0 at
idle.
Yesterday I substituted a 2nd hand gauge I had.
It maxs at just over 30psi @2000rpm,(like it hit a wall),
but is linear from 700rpm idle at about 15lbs up.
Previously I have OH the oil filter/relief assembly.
Next step is to verify with mechanical gauge, but the
behaviour of the gauges suggest they are the issue–
The original message included these comments:
Here’s why I said ‘‘theoretical’’. I had EXACTLY the same problem as you in
that my gauge read 30 when it should have read 40. I could have ignored it
but I thought I would feel better with the correct reading. However, I
In reply to a message from awg sent Thu 14 Feb 2013:
You mentioned in your initial post that the instrument
voltage regulator was working, ruling it out as a cause of
your problem.
Do you have your oil pressure gauge powered by the IVR? On
later cars at least, the OP gauge has its own voltage
regulator (integral with the sender) and needs to be powered
directly from the ignition (12V).–
The original message included these comments:
I have previously swapped senders, which did not alter my
readings, which were max 25psi, and alarmingly close to 0 at
idle.
It maxs at just over 30psi @2000rpm,(like it hit a wall),
Good point, Bob. The power for the oil pressure gauge comes from the IVR
but it is connected to the INPUT of the IVR so it sees the battery voltage.
It should be connected to the double “B” terminal and not the “I” terminal.
In reply to a message from awg sent Thu 14 Feb 2013:
You mentioned in your initial post that the instrument
voltage regulator was working, ruling it out as a cause of
your problem.
Do you have your oil pressure gauge powered by the IVR? On
later cars at least, the OP gauge has its own voltage
regulator (integral with the sender) and needs to be powered
directly from the ignition (12V).
The original message included these comments:
I have previously swapped senders, which did not alter my readings,
which were max 25psi, and alarmingly close to 0 at idle.
It maxs at just over 30psi @2000rpm,(like it hit a wall),
–
Bob Wilkinson, 73 XJ6
Saint Louis, MO, United States
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In reply to a message from Mike Eck sent Wed 13 Feb 2013:
One odd thing I noted over decades with my 3.8S was that the
gauge would read, say 40 during the day, but when the lights
went on it would drop to about 30. Turning off just the
instrument lights, would slowly bring the gauge back up to
its higher reading. I concluded that the heat generated by
the instrument bulb must in some way affect the operation of
the gauge. Strange idiosyncrasies of the Jaguar animal.–
The original message included these comments:
Here’s why I said ‘‘theoretical’’. I had EXACTLY the same problem as you in
that my gauge read 30 when it should have read 40. I could have ignored it
but I thought I would feel better with the correct reading. However, I