I’ve owned my car a little over a year now. My oil pressure gauge has always read 55-60. The last few times out I noted that the pressure was 40-50, but no issues. This eve, I noticed the pressure was dipping below 40 and close to home, read as you see below.😳 When the pressure hit the mark you see in the pic I felt a sensation like the car didn’t want to roll, RPM’s were fine but I thought the car stalled....I was near home and made it fine. I had no trouble revving or reaching speed. I check my oil often and the level is fine. Help....

 

Well, it's either one of two things - (1) the oil pressure transmitter is on the way out, or (2) you've run a bearing or two in the engine. Hopefully it is not '2'. Best thing to do is to get a shop with the right kit, (so one that works on older Jaguars), to check the oil pressure using a direct read-out pressure gauge. This screws into the housing for the transmitter. If the direct reading is the same as you're getting, you would seem to be in trouble, and a more detailed inspection is essential. If a bearing has run, when you drain the oil out you'll see lots of shiny metallic particles in the oil.

 

Agree. Wouldn't panic yet. The sender on the oil pressure system is notoriously troublesome. Mine has failed twice on my Series 2. Once it suddenly started dipping towards zero, next time it just continually under read - I thought engine getting tired! First step is to check the actual oil pressure. A decent garage can do this for you with a capillary guage (mechanical) If oil pressure is ok, I wouldn't get a new sender - I replaced my electrical guage with a mechanical one from SNG Barratt. Never looked back, and now I can be confident of an accurate reading.
If it IS the oil pressure falling, then it does indeed need further investigation. I wouldn't have thought you would have suddenly run a bearing unless you let the oil level get far too low, or had something nasty in the sump. As engines get tired, the oil pressure normally moves down more gradually. Could be the oil pump, a blockage, stuck pressure relief valve? I'm not an expert and there will be far more knowledgeable people than me on this forum, but don't assume the worst. These XK engines are pretty robust

 

I would say its one of several things, but I would start with the easiest first:
1) Bad oil sender - replace and/or install a mechanical gauge at least temporarily. Be careful the threads are British pipe threads.
2) Bad electrical connection, or electrical short.
3) pressure relief valve stuck open or broken spring.
4) internal engine oil leak of large bearing clearances )possible spun bearing)

Hope it is 1 or 2 above.

 

Thank you very much Fraz. I will call my local Jag guy on Monday. This a.m. I started her up and the gauge read as I’ve come to expect (left pic). After 30 minutes of driving and back in my garage the gauge read as seen in the pic on the right. I paid attention to my RPM’s and pull, nothing to note while driving or at idle. Don’t know if this gives any further clues, but figured I’d mention it.

 

What were the revs when you took the photo of the oil pressure with hot oil ? On tickover when hot the pressure can go down quite a lot. I think Jaguar state that the pressure should be around 40 psi when hot. When cold the pressure looks about right, which will reduce as the oil and engine heat up. Other thing is - what oil are you using ? These engines when built would have run on "traditional" oils. The clearances in the bearings are not as tight as modern engines, so you'll be best with 20/50. However, I used to use 15W40 in my 1980 XJ6 with no ill effects. I've also seen 20W40 which is normally sold for motorbikes. but may be OK

 

So, I had a few things done overall since the car was in for a look-see. I purchased differential oil (Castrol axle limited slip 80w-90 gear oil)[size=33px], gear oil (Redline MT-90 75W90 GL-4) [/size][size=33px]and engine oil / filter (Castrol 20/50), had all changed out. I ordered a sender unit and had the mechanic install it. When all was done, mechanic said he didn’t note anything out of the ordinary and stated in his experience, with a cold engine, the pressure is anywhere from 50+, then when warm, hangs around 25 psi at idle and 40+ at speed. I’m wondering if my oil pressure gauge was reading abnormal at always just shy of 60 psi and now reads normal and being reconnected with the addition of wooden gauge surround. 🧐 One thing I didn’t ask about was the relief valve... 😳 I don’t know why he would not have checked the pressure manually, which I may call on Monday and ask him to do.[/size]

 

So the problem was as we thought the sender - next time though, rather than replace the sender, I'd go for the capillary replacement. Far more reliable and accurate.

 

Excuse my ignorance, but what is a capillary replacement?

 

Instead of an electric sending unit and receiving gauge, a capillary unit is purely mechanical. It uses a small tube that is pressurized with oil from the engine and connects to the gauge directly to give a reading. They're simple and pretty bullet proof, unless the capillary tube springs a leak, then you'll get oil oozing out behind the dash.

 

Yes, exactly that. You can get then from SNG Barratt. Work very well and not tough to fit, although my local Jag garage fitted mine for me. Here's a link to the guage on the UK site:
https://www.googleadservices.com/pag...gQIARBF&adurl=

Looks just the same, except that it reads to 100 psi - needed, because my engine cold will easily go to 70 or a tad more until hot. Tested against a professional guage strapped to my window, and it read identically