Saw oil patches on the parking floor a while ago and found oil missing by slightly more than 2 litres!

Found the source of the oil leak. It was dripping from the oil cooler bypass (I don't have an oil cooling kit which is optional for the XJR). The mechanic removed the bypass and found 4 hardened O-rings which broke on first touch. The O-rings were replaced; Rose got a new oil change and all is well now. Forgot to take pictures of the bypass and the O-rings but there are plenty looking similar at the X40 chapter. See Oil Pressure Sender.

Backtracking a little, Rose was running fine with no abnormal signs; oil pressure reading always pointing nearly middle (see picture).


Have been wondering why the needle always rests at the same spot regardless of oil level, engine load or throttle position. Then found this earlier post saying that such is the result of Jaguar original settings. Some earlier attempts by others to produce a more responsive reading can be found here: Oil Pressure Sender Series III X300.

My take-away from this incident and these two past discussions is, check your oil regularly and never trust the "idiot gauge". They name it right!

 

Since the oil pressure sender is a discrete switch it shouldn't be hard to put in a red light or a fuel pump shutdown through the inertia switch wiring

 

The 'idiot switch' will only light up the low oil light when there is approx 2l of oil left. When it gets to below 3l of oil the oil pressure will drop to 0 while turning/cornering. It is a crappy design but on the other hand I saw a car driving with 2-3l of oil for at least few months(lots of miles too) few years back and its still perfectly fine today, clearly a bulletproof engine design.
If it bothers you, you can always replace it with the old type, they are still available, otherwise as you said yourself, check the oil regularly(well at least once a month).

 

Bear in mind the the temperature gauge operates in almost the same fashion. The needle will remain fixed in the middle over a wide range of temperatures....moving towards the high end of the scale only when xxx-temperature is reached. I don't know what that magic number is. On my XJR/6 the needle touched "N" at 170ºF and remained fixed until (at least ) 205ºF...which is the highest temp I saw on my scan tool at the time.

Cheers
DD

 

While there is a fix for the oil pressure gauge by using an older version of the oil pressure sender, is there a similar fix for the temperature gauge? The "normal" temperature is worrying. My mechanic said that the oil that was replaced was thick and almost black, which indicates that the oil had experienced high temperatures, less than six litres taking on the normal loading of 8 litres. A more sensitive oil pressure and/or temperature gauge would have alerted the driver of anomalies.

My another finding was the coolant bottle has shown signs of vapour leak from the seams of the bottle. Water level is below minimum on cold check, but not low enough to trigger the warning light.

The factory tolerance level of the three critical monitors, i.e. oil pressure, engine temperature and coolant level, is just far too excessive to justify peace of mind.

 

Aholbro1 made these pics a few months back and is a reminder of how the stay ahead of the game .

https://www.jaguarforums.com/forum/x...l-pics-160138/

 

Oh, I missed this good write-up with pictures by Aholbro1. Thanks for digging it up.

 

O - ring part # s

https://www.jaguarclassicparts.com/u...-3-2-4-0-litre

 

It is always useful to mention the part number and where to get it. I notice that Classic Jaguar Parts defaults the quantity of the O-ring needed as 5, not 4. Wonder where the 5th one is fitted.

 

On the ground and rolled away, hence the "spare", very thoughtful I reckon.

I simply used 4 o/rings from my selection grab pack for the "Poverty pack" and the R, and no leaks.

 

At the risk of tempting fate, I suppose that it is a considerable saving grace that we have yet to hear of an engine expiring through oil supply or overheating problems? Maybe Jaguar got it right; idiot gauges make for a quiet life all round!

 

Found that the rationale for the idiot switch was fully explained in Jaguar TSB 15-13. I would not worry as long as (a) the oil pressure gauge does not read zero; (b) there is no warning light, and (c) I checked the oil level every two weeks.