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Oil Pressure

leo_denmark
Posts: 767
Joined: Sun Sep 11, 2011 6:32 pm
Location: Denmark

Re: Oil Pressure

Postby leo_denmark » Sat Jul 15, 2017 2:02 pm

leo_denmark wrote:I have now replaced my old, faulty sender with a C46272 from David Manners. This is supposedly a proper oil pressure measuring device used at older V12 and XK engines and not the on/off thing used for late XJ40 and X300.

I ended up with 90 ohm in series to get the same 6 bar oil pressure cold as I had before the change. I see a small pressure increase when revving it, but not much. I allowed the engine to warm up in idle, and the pressure dropped a bit to around 5.5 bar. I would have expected it to go lower, but a real drive will show if I get same readings as before.
My old sender would drop to zero at pressure below 3.5 bar, and that would not happen after quite some miles when RPM drops

With no resistor in series the needle moved out of the scale.
220 ohm in series resulted in 1 bar indicated at cold idle
Sender unit resistance at 0 bar: 330 ohm, dropping when pressure increases. Hard to do a proper test using a handheld compressed air gun...

I will update after having driven the car.


Conclusion is that I need a resistor a little bit smaller than 90 ohm, as oil pressure in warm idle now displays as 0.2-0.4 bar with the oil pressure lamp on. Another possibility is of course that my pressure has dropped to this level from around 1 bar during the 2-3 years of use with dead oil pressure sender, but I honestly don't think so

752120
Distinguished Mbr
Posts: 1039
Joined: Wed Jun 25, 2014 7:10 am
Location: Warrington Cheshire

Re: Oil Pressure

Postby 752120 » Sun Jul 16, 2017 9:29 am

oops wrong thread sorry

xjr40
Posts: 1687
Joined: Sun Jul 01, 2012 6:18 pm
Location: Canary Islands, Spain

Re: Oil Pressure

Postby xjr40 » Sat Dec 07, 2019 7:30 pm

Looking for answers on a possibly faulty sender on one of our local group of XJs member's car. I suspect reading absolutely nothing, then normal pressure is the sender...?

Recovering this thread... as my own oil pressure gauge displays different readings, cold, warm and depending on idle or higher rpm, can I assume it has a "proper" sender not just the on/off variant?
1991 Jaguarsport XJR 4.0
One of 83 manual - 65 LHD
Regency - Magnolia
Previous 1989 XJ40 2.9 auto (3.6)

pimgmx
Posts: 3440
Joined: Tue Jul 08, 2014 12:07 pm
Location: South East of the Netherlands

Re: Oil Pressure

Postby pimgmx » Sun Dec 08, 2019 1:16 am

Yes and yes... ;)

the daily: 01 S8 http://bit.ly/2kIwP4m
the eyecatcher: 93 Insignia http://bit.ly/1iGrmsU
the GT: 89 XJS http://bit.ly/1WQGpC5
the diva: 88 Biturbo SI https://bit.ly/3dzdvAL
the ex: 93 3.2 http://bit.ly/14GTNrq

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Oil Pressure

Postby naki_k » Sun Dec 08, 2019 1:21 am

They all fail sooner or later.
Quite simply, it’s time to buy a new one.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300

xjr40
Posts: 1687
Joined: Sun Jul 01, 2012 6:18 pm
Location: Canary Islands, Spain

Re: Oil Pressure

Postby xjr40 » Sun Dec 08, 2019 9:45 am

Thanks thought so too. I said he should change it. And I'm glad mine is the true type lol
1991 Jaguarsport XJR 4.0
One of 83 manual - 65 LHD
Regency - Magnolia
Previous 1989 XJ40 2.9 auto (3.6)

Swe_Jag
Posts: 1
Joined: Sun Feb 19, 2017 10:27 am
Location: Stockholm, Sweden

Re: Oil Pressure

Postby Swe_Jag » Wed Apr 22, 2020 9:21 pm

Summary,
I have problems with low oil pressure when the motor is warm and I am looking for information about what readings other people get in their XJ40’s when the motor is warm.

The details,
I have with interest read all about the pressure reading in this thread. In my XJ 4.0s (-94) I have the oil pressure meter with 0-8 (bar?) on the scale and 4 straight up. When the engine is cold, I always get a reading of 4. No matter if the engine is at idle (600 rpm) or at 4000 rpm.
But when the engine is warm, the pressure drops to about 1-2 bar when motor is in idle at 600 rpm. On very hot days, after have been driving for a while, it is not uncommon that the pressure drops down to below 1 bar in idle. But it comes up direct if I give it some throttle and increase to above 1000 rpm.

I have seen the notes about that this meter sensor is known to become bad and that people have replaced the sensor with a resistor. But I have reasons to believe that my problem not is a sensor error. This because I read somewhere that the red oil pressure warning light has its own sensor, independent from the analog meter. And that the red warning light turns on at 0,5 Bar.

Before I changed oil recently, I was using a semi synthetic 10W40. During hot days when I ended up in a queue after hard driving the meter fell down to 0,5. And then the red light start to flicker which made me worried.

I got at tip to try thicker oil and have now changed to a very expensive 20W50 mineral oil that is to withstand high temperatures. The problem became a little bit better but the analog reading still falls below 1 at idle duringhot days after driving for a while. But I have not seen any red light yet.

So, I am very interested to hear what kind of readings other people get at the 6 cyl. cars. (At cars with working analog meters. Where the sensors not have been replaced with resistors)

I am also starting to think if this issue is related to the coolant system. The motor temperature seems to be perfect. That meter is pointing straight up after just 5 min of driving and the reading is very steady. But I am thinking if air-pockets in the coolant system can cause hot spots in the engine that will cause the pressure to fall. Just an idea.

If any one out there has ideas on this, I would be very interested.


Regards,

Patrik
1994 Jaguar Xj6 4.0s
1962 LandRover 88" Ser. IIA
1997 Citroen XM TCT

abercanadian
Posts: 1500
Joined: Tue Oct 16, 2012 6:50 am
Location: Vancouver Island

Re: Oil Pressure

Postby abercanadian » Wed Apr 22, 2020 10:05 pm

The oil light is the same as the gauge, it will come on when the gauge indicator is low. They are linked, not separate. You have a failing sender, change it.

Larry
94 XJ40 VDP vin 701729
Oyster Metallic/Doeskin on Aero Alloys
240,000 km/149,000 Miles
Daily Driver

94 XJ40 SOVEREIGN vin 703632
Diamond Blue Metallic/Barley
111,000 km/69,000 Miles
Parts Car

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Oil Pressure

Postby naki_k » Fri Apr 24, 2020 1:19 pm

Ditto. Standard fail of the oil sender. Cheap fix.

If you had genuine low oil pressure, you would hear some bad noises from the engine.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300


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