I have a 2001 XJ8 with 260,000 miles on the engine. It runs great. However, the low oil pressure indicator started coming on once in a while when I started. It would and stay on for a minute before turning off after I drove for a little while. Because my driveway slopes downward (trunk lower than hood) I have assumed that the angle of the car contributed to this and wasn't worried.

When the weather got chilly last week, the light came on, went off as usual, and then turned back on after I drove for a while (first time it had done that). Due for an oil change anyway I went straightaway and got that done using synthetic oil. The tech said not to worry, that the engine is burning a little oil (no surprise) and that the fault indicator likely stemmed from the oil level being a bit low.

Today it got colder, and the low pressure indicator came on after driving for a few minutes. About the moment I was getting worried, it turned back off. (The car also stalled at a red light - first time ever). Should I be worried that the oil pump is failing? Is this indicative of something I need to address immediately? Or is this just an old car that needs to warm up to establish solid oil pressure? With a topped-off crankcase and fresh oil, I have limited the options on what is happening.

It makes me very nervous to drive more than a few seconds with a red light glowing on the dash!

 

You might want to check your oil pressure sending unit.

 

You are right to be nervous. You changed the oil. I assume the filter too? Clogged filters will cause low pressure. What viscosity did you use? The extremely cold weather we're all having here may have an impact but I would assume that problem on start up.
You don't mention any noise (tapping, knocking) which, in conjunction with a low pressure light, would indicate you're a stones throw from seizing.

I'll start by saying, with 260k miles, the most likely cause is
worn bearings
worn valve guides
worn pistons, rings etc.

Oil pump itself is a possibility. The pressure relief valve within it, worn clearances, etc.

Also consider the oil pickup screen being clogged, fallen off, the pick up tube.

Then there is the most basic. Check the sending unit. Disconnect it. If the idiot light is still on, you have a short. Then put a gauge on it and vefrify the actual pressure. Sending units usually trip at very low pressure, but they also fail.

These are what I would start with personally and in reverse order, assuming I was hell bent on keeping the car. If I found any bearing wear, the cost to overhaul will outweigh the cars value for sure. The cost of replacing the engine with a lesser used engine would also likely outweigh the value. I would then have to consider sentiment over cost of ownership.

 

That and get an actual oil pressure reading. Repair shop should be able to hook up an oil pressure gauge. Either way the longer you wait the more damage you might be doing, better safe than sorry.

 

Welcome to the forum. I've moved this thread to the X308 section, your 2001 model is an X308.

When you get a moment stop by our new members area and introduce yourself.

 

First of all, I would avoid the tech who said not to worry about oil pressure warning. For me that warning is the most important engine warning. I would not be too concerned if warning light was flickering at idle, but once rpms are up from idle - light must go off.

Obviously check the oil level. Every time after oil change I find that oil is barely over minimum mark, fill it to max mark. These cars drink more oil as they get older.

Lots of good suggestions here already, I would check wiring and tripping pressure of the sensor first .

 

Let's *** u me for a second the sending unit is good (it is flickering, it is majoring something), most probable cause becomes piston rings. Maybe some RISLONE or SEA FOAM in the oil to clean the rings,and the oil pump, and then new oil of a heavier viscosity (maybe mobile one for older engines 5W 40).

But at 260,000 miles you have had your money's worth. Congratulations on that.

 

Let's apply a little thought here. Problems with a worn engine normally first manifest in an oil pressure light that comes on at high oil temperatures - when the oil is thin, and the pressure drops below the threshold to turn on the light.

You have an oil pressure light that comes on when the engine is very cold. This is normally the time when oil pressure is at its very highest. This suggests that the oil pump is having problems pumping the oil in the first place.

This could be :

A combination of low temps and high viscosity oil means the pump is losing prime and / or not pumping. The solution for this would be (counter-intuitively) thinner oil - especially one with a lower "w" number - say 5w40 instead of 15w40, for example. This is a problem well known in the Land Rover V8 - it can be hard to find an oil thin enough for cold weather to pump at all, and thick enough when hot!

In answer to your question, yes, I would be worried that your oil pump is failing or worn (or something else, is the pickup clean?).

Your symptoms do not fit with the usual "worn engine, hot oil, light flickering" scenario.

Pouring snake oil in is going to do bugger all apart from make your wallet slightly lighter.

This is all guesswork anyway, without attaching an oil pressure gauge. This is the most important step to figuring out what is really going on.

 

"most probable cause becomes piston rings"

Piston rings are lubricated by spray from the bearings and sometimes the wrist pin. Thus worn rings cannot cause low oil pressure.

Here's a list of possible causes of low oil pressure I found.

Excessive main and rod bearing clearances.
Worn main and rod bearings - the most common cause in high mileage engines, or engines that have been poorly maintained (infrequent oil and filter changes).
Worn crankshaft journals.
Worn camshaft bearings or excessive bearing clearances.
Assembled rod, main or cam bearing clearances that are too great.
Worn oil pump or excessive clearances inside the pump.
Oil pump relief valve stuck open.
Low oil level in the oil pan - usually due to oil leaks or oil burning (worn valve guides, valve guide seals, piston rings, cylinders).
Too much oil in the oil pan - causes aeration and foaming.
Plugged oil filter.
Obstructions in oil pump pickup screen.
Loose fitting oil pickup tube.
Improperly installed oil pump pickup (too high in oil pan).
Leaks between the oil pump and engine block.
Cracks in oil pump housing.
Cracks or leaks in oil galleries or gallery plugs.
Oil viscosity too thin for hot weather.
Oil viscosity too thick for cold weather.

 

Mark, you are probably right: stiil, I am fixated on the very high mileage . . . Oil pressure check along with a compression test, maybe . . .

Wait, it is MN; lighter oil should be first choice . ,

 

I think you're right - I just sold a Land Rover Discovery with the old Buick V8 and this was a very common problem in cold states if the oil is too thick.

If you look at the oil viscosity chart in the handbook, use the local minimum temp to choose the viscosity.

 

below freezing in Memphis this morning. Let's see how this looks today - great suggestions - headed over to get oil pressure reading at shop.

 

Drop the oil pan.
Replace the oil pump.
Pull the caps off of every connecting rod and main bering and replace inserts.
Some of the main bearing uppers may be hard to move.
Don't worry about the upper mains that are hard to move, they don't wear much.
Use a torque wrench.
You will get quite a few more miles out of her.

I recomend a high volume oil pump if you can get one.

Put some Lucas oil additive in her to compensate for compression loss.

Wally C.
03 XJ8

 

That's not possible with the Jag. The main bearing caps are incorporated in the windage tray (maybe wrong term) that bolts to the block. You have to remove the engine to access them.

 

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Dratz................I wonder what pencil pushing bean counter designed that.

Anyway, I would change out what I could and replace the pump and then experiment with bumping up the viscosity of the oil.

If he can find a high volume pump it should compensate for the oil demand of the old engine and keep the pressure up..

Maybe a straight 40 weight.

I have kept a few old beaters running by going higher and higher with the oil viscosity.

Harley oil is 20-50.

Just a thought.

Wally C
03 XJ8 x308

 

The only problem with your suggestions is that the OP's symptoms do not agree with bearing wear. Again : he has low oil pressure WHEN COLD. Bearing wear normally shows up when the oil is HOT.

 

OK

Riddle me this:

Why do worn mains rattle when first started and then quiet down unless RPMs are increased increadibly.

It's hard to look for totally logical answers when dealing with a worn out engine and oil pump.

Every one of these arguments are valid.

The cost of changing a few inserts and oil pump is insignificant if he can nurse a few thousand and maybe a bunch more before throwing in the towel.

Simple procedure that can be done in the driveway by anybody that has been a back yard mechanic. Mark the bearing caps and bolt heads and do them one at a time.

I was a auto wholesaler during the 70's and 80's.
I have seen all kinds of crazy symptoms.
I had one car that would not idle and would barely move. I figured out the compression was weak. Changed the oil to 40 weight and added one can of stp oil treatment. The purchaser drove it for several years more.

I noticed that a lot of Fords V-8's had oil lights flickering at 80,000 miles and above. Re-doing the bottom ends and oil pump solved the problems, end sale dealers reported cars running for many years more because they were traded back in.

Never had one come back with a blown engine.

Wally C

03XJ8 - x308

 

trpwire-
Please advise the procedure to change the oil pump on an XJ8 after pulling off the oil pan!

And... I guarantee you that the bedplate design lower end on the engine was NOT designed by a bean counter.

I assume you are just trying to be helpful, BUT, before giving advise, you should know something about the car you are talking about!

 

I'm commenting on this thread a little late. I was searching for information on oil pressure readings. Jag doesn't document the oil pressure they require. They count on this oil sender to do everything rather than put a real pressure gauge up on the dash. My Chevy truck has a pressure gauge. You would think that a car as expensive as a Jaguar would have a gauge. Not just a light.
Jaguar had an early problem with their V8's. They had early failure issues with the cam chain tensioners. The chain guides were a polymer and would begin to break down prematurely. When the guide broke down it broke up into pieces. These pieces would clog up the oil pickup and murder the engine. I learned this the hard way when I purchased a used 1998 XJ8 that wouldn't run. I knew I was getting into something. Just didn't know what. The car wouldn't start. I pulled the engine and pulled it apart to find the clogged oil pickup and scored bearing journals on the rods and the crank. I didn't think this was a problem until I went out to buy these parts. Jaguar is no longer making these bearings and they are very, very hard to find and even more expensive. So beware with these early 4.0 V8 engines.
This why so many of these are parted out when the bodies look great.
I was eventually able to buy all the bearings. I started this engine for the first time today. I was concerned about the oil pressure given the engines history. So I did install an oil pressure gauge on a tee fitting with the sender unit and mounted the gauge in the engine compartment. The gauge reads about 65-70 psi. But I am getting an intermittent oil pressure warning from the sender. So I'm wonder what is the permissible min-max oil pressures on this motor. I plan on ordering a new oil pressure sender and see if that clears this problem.

 

This is a late reply but I hope it helps anyone who reads your post. There is nothing simple about replacing these bearings in a Jaguar V8.
The engine has to be pulled and the block is split to access these caps. The caps are integrated into a section of the block. It's one big part.
A person needs to tear the entire engine down to the bones to do this job. Unless you have a later model XJ8. I don't recommend this.
Maybe after 2004. But you need to check on the availability of these parts. Jaguar stopped making these early model parts and there are
no aftermarket parts like this either. I though Clevite would have them but they don't make them either. Jaguar bearing are very specific.
Theses parts are all coded and stamped. You will find codes on the crank. The rods and the crankcase. The engine are stamped with these
specific codes that need to be matched to a chart for each bearing and application for the mains and the rods. I would say "just buy a rebuilt engine".
But the engine re-builders are having the same problem getting these parts.
I don't really know how Jaguar is supposed to have a legacy if they are unwilling to provide the parts people need to restore these cars.