I have a 1986 XJ6 that I acquired about a year ago, currently with about 110k miles on it. Ever since I bought it I've been a bit concerned about what I believe is too-low oil pressure. It will only rise to about 40 psi 'at speed' while still cold, and will often drop below 10 once warmed up and sitting at idle. (And mostly lives between 10-20psi while driving once warmed up. Always lower than the 10 psi per 1,000 rpm that some suggest.)

I took it to a reliable mechanic who initially felt it would just be a faulty sender. BUT, they ended up saying that sadly, it wasn't that, but rather worn bottom end bearings 'giving away too much of the pump's flow', apparently. Repair cost north of $3,000

That's not in my budget for that car for the moment, so I'm just enjoying the car by driving it carefully, and locally.

BUT, my reason for this post is that I've been noticing recently that the pressure will plunge enough to turn on the warning lamp when making a left-hand turn -- with the oil well up into the safe range on the dipstick. (I'm running 20w50, FWIW.)

Given the size of the sump on this engine, that seems very odd to me. It has me wondering if perhaps I have a problem with some kind of 'wonky-ness' with the oil pump -- and of course, that has me grasping at the straw of hoping that may be the root of my other problems as well...

Anyone else have a similar experience? And if the pump might be at least part of the problem, is that replacement a huge task?

Any advice is appreciated...

 

The oil pumps are generality very robust. Depending on your tools and DIY ability, it is possibly to drop the sump to gain access to the oil pump, although it's not the easiest thing to do. The pickup tube is sealed to the pump with an O ring, and that may have gone hard over the years and isn't sealing.

Again not easy, but it can be possible to change the bearing shells with the crank in the block. Probably easier to pull the engine and work on it on a stand though.

 

Thank you.

So the oil pan can drop without the need to remove other cross-members or parts of the steering or suspension etc? If so, that is something I feel I could tuck into at some point...

I do actually have a plan to possibly remove and rebuild the engine at some point in the future, but for now...

Thanks again for the reply.

 

It's been a while since I've looked under a 6 cylinder XJ, but I think you would need to drop the front suspension. It's not that hard to do.

 

A 110K miles should not have worn the bearings to the extent quoted.
Did the mechanic check the oil pressure with a direct reading gauge?
I have seen the low oil pressure symptoms you describe on a few occasions in XK engines with moderate mileage and it has been a problem with the oil pressure relief valve.
Has anyone checked the oil pressure relief valve?
A partially stuck open relief valve will give you these symptoms.
A worn relief valve face will also give these symptoms.
I suggest checking this area before committing to an engine teardown.

 

Much as Bill wrote, for low pressure on the gauge, first check the pressure with a mechanical gauge as the most likely cause is the gauge or sender. Second, the pressure relief valve. Third, the oil pump. And last of all bearings.

For the low pressure on turns, are you sure that the car has the correct dipstick?

When did you last change the oil and filter? Do you know how much oil it took to fill the sump?

 

Further to what Peter said, there is a hole in the baffle plate in the sump that the dipstick goes through. What I seen in the past is the dipstick misses that hole and instead rides on top of the of the plate. Oil is added until it shows "full" which is actually several liters overfull. The oil then gets frothed from the crankshaft hitting it and can result in low oil pressure, as it's an oil foam, like the foam you might get on a fancy coffee.

 

Thanks again everyone for weighing in with your insights!

I just thought it would be appropriate to follow up with a little 'closure' to this saga...

A couple of days after the last post, I was out with the car, with it behaving as usual, and stopped to fill up. When I got back in the car to return home, it wouldn't even turn over -- hydrolocked!

I imagine this is connected in some way to my prior complaint, though I don't think I could have predicted this. Anyway, I had the car towed home, and the next day decided to turn the key again to see what would happen. To my surprise, it turned over and purred to life. HOWEVER, shutting it down, I checked the fluid levels and found the coolant to be low, and the dipstick to be high. WITH FROTHY CHOCOLATE MILK!!

At this point, I'm guessing I've blown a head gasket. Possibly worse.

I had already had it in mind to rebuild another engine to swap into this car -- perhaps that 'maybe' just got turned into a 'must'. Anyway, sadly the car will be off the road for a while. Not the news I wanted to share...