jaguar low oil pressure

[wallacedog]

HI all i have a problem with my 94 xj40 oil pressure, after about 20 miles the gage drops to near nothing, it is fine till the engine gets hot. Somebody told me that it could be the oil sender unit that has got a fault i hope that is so. I phoned the man that i got the car of he sead it as been like that for a long time and i should not be to concerned, easy for him to say.Any advise whould be appreciated.

 

[Dave Russell]

Hi & welcome to the forum.
I'm not a Jag expert, but, I would verify the oil pressure by connecting a mechanical gage to the block. If the pressure is below about 40 psi at 2500 rpm, there is cause for worry. Make sure that you have the correct grade of fresh oil & filter. The pressure senders have been known to go bad, but I would verify with a mechanical gage first. I'm sure that someone more knowledgeable than I will join in. Maybe someone can tell you exactly where to connect the gage & what it should read.
D

 

[shorn]

I just replaced the oil pump in my Austin Healey because of low oil pressure (see post "Which Oil pump to buy" under Austin Healey. It raised the pressure somewhat. Good luck. However, if the guage shows pressure when the oil is cold, but drops significantly as the oil heats up, I would suspect the guage is functioning correctly and there is a problem elsewhere.

 

[Webserve]

The oil pressure sender on the XJ40 is one of the notoriously bad items that Jag put onto these cars. It is one of many common ailments that these cars suffer from. My '88 XJ40 oil pressure bounces all over the place depending upon time of year, time of day and temperature of the oil as well as the RPMs of the engine. It is a common malady. You can usually find a replacement unit for about $25 on Ebay or from an aftermarket place for about $40. Since this is a well known problem, I would give this a shot before I started to pull oil pans and pumps.
There are two types of senders available. One is the simple on/off type that will put the gauge at dead center every time the engine is started. The other is the gradient type that will go up and down as the engine pressure goes up and down. It is pot luck as to which you will get. The sender is located just above the oil filter on the left side of the engine and it is recommended that you change the oil at the same time as the sender since you have to take the filter off any way.
Since it sounds like you just purchased this car, you need to read the online book written by XJ40 owners. It is located at https://www.jag-lovers.org/ebooks/bookindex.php?Vbook=xj40. It will give you an idea of the problems these cars face as well as how to fix them.

Webserve

 

[maynard]

I was alking to the guy from Jag Specialists yesterday. He commented that many of the low oil pressure problems come from using the wrong oil and/or filter. He says to use only Castrol, 20W50 in summer, 10W40 in winter. He also said to use only factory oil filters.

I don't know if this is the case, but an oil change is cheap and can't hurt.