This has happened to the car once before. I'll be drinving along and then when braking for a red light and coming to a complete standstill, the oil light flickers and the pressure gauge drops below 20psi momentarily before slowly climbing up while stationary.

It's like the oil is rushing forward to the front of the sump, away from the pick up? Last time I topped up the oil (that was still within the limits, but at the low end) and all was well.

This time the symptoms are exactly the same but, I topped up the oil last weekend? I haven't checked the level yet as it's still cooling down but, I going to guess that it's still within limits.

The weather has been warmer recently so the car has been running a little hotter but, again, still within normal limits.

Advice appreciated.

 

It's a few years since I ran Series I and II 4.2 XJ6's but I did have to do a lot more engine work in those days.

My first thoughts would also be oil surge away from the Oil Pickup on braking but your recent oil change precludes this possibility.

This leaves wear in the Oil Pump itself or an issue in the Oil Pickup.



I have come across an instance of an Oil Pickup pipe loosening at the flange so the Pump was pulling air with the oil.

It could be the gauge. Before going any further, a pressure check with an external gauge may save a lot or worry and work.

Graham

 

I'm with Graham.

There is a HUGE bowl at the rear of that sump, with about 8+ litres of oil in it. Surge up and out of that bowl would require a SERIOUS panic stop.

I would do the mechanical oil gauge test FIRST, as the Smiths oil sender is known hissy on any day. However, the fact these have 2 oil switches, and both seem to be showing a low pressure issue, is a worry.

Many, many items come to mind, but please do the test with the mechanical gauge before we start listing all sorts of internal adventures.

 

Thanks for the replies guys. I'm going to check the oil level in the morning just to make sure I'm not losing/burning oil and that is the reason for the loss of pressure, although it seems it would need to be burning a bucket load?

 

FWIW I had the same thing happen on my Ser III a two times over the course of several years....and others have reported the same.

Others here have made good remarks/suggestions but I'll just add that testing with a remote pressure gauge is not likely to reveal too much unless you configure the hook-up so that the remote pressure gauge can be left in place, allowing the independant reading to be compared to the dashboard gauge and light at the very moment the symptom appears.

In others words, testing when everything appears to be working normally is unlikely to reveal anything but "normal" results.

The other alternative, as mentioned, is to start digging into the engine internals. An awful lot of work to be undertaken on such fleeting evidence of a problem.

Anything involving oil pressure tends to make us nervous, naturally. OTOH, trying to isolate a fault based on such a fleeting symptom may not be easy. In such cases you might move heaven and earth and still not conclusively identify the problem.

In my case, a cursory check of oil level, and the lack of any noises to suggest that something horrible was happening, brought me to the conclusion that I should do absolutely nothing. And that's exactly what I did :-).

Not saying that's the right answer for everybody but ....heh heh....it worked for me. Each of us has different levels of concern over such problems, not to mention different levels of dedication to solving them :-)

In the deep and distant pits of my memory I vaguely recall some guys having issues with pressure relief valves. That might merit some discussion here.


Cheers
DD

 

OK, I've checked the oil level this morning with the engine cold and the level has definitely dropped since the last top up? When checking the dipstick the level was a 1/3 of the way up the crosshatched area, so definitely not low and the dipstick had 340/4.2 written on it, so appears to be the right dipstick for my engine.

I've topped up the level to about 2mm below the top of the crosshatched level but, it did seem to take a lot of oil to get there, probably about a litre.

The car is due for a service this month so I might get a couple of oil filters and change the oil with some cheap stuff, run it for a week and change the oil again with some better quality stuff.

 

Hi Woz, I would assume that in the last 30 years, the engine has been molested.
If so, the molester may have left the baffle out of the sump.
Also, the oil pump lives at the front of the motor, with a long pickup pipe running to the back of the sump, and this is sometimes bent upwards, which would allow it to draw air under braking or acceleration. You should be able to run an extra half litre in the sump with no problems.
The mechanical, 50mm Smiths oil pressure gauge is a drop in replacement for the electric one.

good luck

 

Fredd,

That's what I was thinking, that a baffle was missing which made the level critical when braking.

 

Certainly plausible but in that case I'd expect the symptom to pop up regularly and be easily repeatable

<shrug>

OTOH, problems do not always manifest themselves in accordance to my logic :-)


Cheers
DD

 

I drove the car to and from work today and tried some heavy braking and the oil pressure stayed rock solid at 40psi?....

I should also add it was pretty warm too and the temp was at the upper end of normal.

 

Were you expecting something else? :-)

I don't see any easy answers. You'll have to decide how much time, effort, and money you want to invest to isolate a problem with very fleeting symptoms. I'm thinking you'll have to pull the sump and hope that an obvious fault pops out at you. On these cars pulling the sump means pulling the engine? I can't remember.....

Adding an extra 1/2 litre of oil sounds good to me. Of course, when the symptom is so intermittant to begin with it it'll be hard to know if you've done any good or proven anything.

Cheers
DD

 

Kind of a way out there guess, The sender! A couple of years ago, the Jaguar sensor in my car began to act flakey. Slow to read and reading sometimes normal and sometimes weak. But, the engine showed no signs of lube shortage. I went shopping for a mervhnival guage. No luck, amazing. I expected to get one of thode with a bravket fort under the dash mounting and a plastic tube. Uh, uh, So, I got an accessory electric guage. I managed to plumb in both! Eureka, The Jaguar guage and it agrred whern pressure was normal, and then on swithing, the accessory gusge shoeed normal and the Jag guage wimnpy on the Jag sensor! So, for a time, I just hooked the accessory sensor to the Jag guage and ran that way for a time. Then, for somewhat unrelsted reason, I replumbed. This time with a NOS Jag sensor from David Boger. All has been just right since then. The guge id s bit slow on start up, but, I hear that iy is a normal symptom and to to be alarmed at.

Bailey got me up at three thirty AM, we went out, he took care of business, came back in, wanted and got his breakfast and then back to my recliner and to sleep. Little does he know that I buried his medicine in his food and he ate it!! Vet appointment today, they want a stool sample, Mebbe I can find it at daylight!! No luck, even with a flashlight at 3 AM!!

Trip in the Jag, of course. Gotta move it any way to get at my brass fitting cans. Dishwasher needs replumbing. Mouse ate the rubber lines!!! I have some detterent for them and a tube of foam to fill a suspect hole behind a base vinyl. Or, I may make some wood base for that section behind the was a portable, but is no longer dishwasher.