My oil pressure gauge has been reading all over the map, but tonight it was low and the dash light flickered.

I checked the oil level and it reads full... the oil on the dipstick looks clean; though I was thinking that I should have the oil changed. Would this help?

What should I look at/for? Is the dash light linked to the gauge in a way where a faulty sending unit might cause these? Is there a way to test the sending unit?

Thanks

 

On the '85 V12 you have 2 oil senders on the post at the rear centre of the engine, behind the throttle pedastal.

The one right on top, the bigger one, is for the gauge, and known to be erratic at best, and leaks oil.

The one on the side, usually facing the "A" bank, and the smaller one, is for the light, and is known to leak oil, and give erratic light flickering at times.

If this occurance was/is at idle with the engine HOT, and in "D", then it is sort of normal, as this engine idles quite slowly, so hence the oil pump rotates equally as slow, if at other than idle, STOP.

The ONLY proper way to verify the oil pressure is to attach a mechanical "master gauge", usually to the light sender port, and note what the oil pressure is actually doing.

Mine has 30psi at idle "hot", with 10W/40 oil. Bear in mind that the Jag spec is ??psi at 3000rpm, what happens outside this rev spec is obviously not of concern??, dunno.

Once you have the actual psi with the master gauge, you will have peace of mind, or other advice can/will be given.

 

Those were the conditions; I think I'm fine. I'll keep an eye on it.

Thanks!

 

Just to jump on this thread.
My '86 XJ-SC V12 used to have what I call normal oil pressure indications cold ~65psi then driving hot probably about 65-75 psi.
Recently, cold 50psi, hot ~55psi the next start it might indicate normal.
It is very erratic. Sometimes it will jump up to normal and then stay there when I go around a corner. Oil level is OK.
So it does not fluctuate, but seems to stay on what it wants until another start or change in vehicle direction. Strange.

 

Grant's advice applies equally well to your situation, HeyCharger. A stand-alone gauge is the only way to verify what your actual pressure is. The gauge electrics are flakey....but easily sorted if you have the will. New sender and switch, clean/repair connections at same, clean contacts at the back of the instrument cluster.

IMO.....

The oil pressure gauge is almost just a novelty item with these engines. Actual oiling system failures are rare on these beasts. A known-reliable warning light is probably all a person really needs. But most car guys like to have the gauges to keep us amused.

My own gauge functions well but consistently reads too high. I shrug it off, to be honest. Does the gauge show some pressure? If the answer is "yes", I'm OK But as I age I find myself becoming nonchalant over things that I would've fussed over decades ago.

Cheers
DD

 

Thanks Doug. I may install a direct gauge. I did this in the fuel line when the pressure there was suspect.
Thanks.

 

Gauge is usually guess work unless you do the above and clean and verify all. With 20w50 or better oil (10w60 motul) you shouldnt have issues. Believe me my car will spray oil like a cat in heat and I've never had actual pressure issues, just alot of smoke and weekly top-ups.

chevron delo 15w40 is fine for my climate, once a retarded mechanic refilled with 0w20 and my WARNING light came on dumped the oil and refilled with thick chevron diesel synth oil...warning light never came on again. Oil sys is bullet proof on the V12

 

Jaguar's answer to the low oil pressure indication for the 1994 V12 sedan was to install a pressure switch like the AJ16 X300 sedan.

Copy of the TSB for info.