SORRY, SORRY, SORRY - Just realized this in the wrong forum

Could someone with admin priv's move this?


Howdy all

I had the experience of oil pressure dropping as I accelerated. Pressure was good at idle.

After much reading I decided to first check if the timing chain tensioners had worn out or cracked. Popped the valve cover to find that the timing chain was practically new. Nice to know, but didn't provide a diagnosis.

So after more reading I decided to check the oil pressure directly off the filter base. Using a mechanical oil pressure gauge I determined that the problem wasn't the sending unit or the dash gauge.

Next I decided it was time to bite the bullet and drop the oil pan to get an eyeball Mark I review.

Now, I have never opened up a Jag V8 before, but I am pretty sure the oil pickup isn't supposed to be full of plastic chunks:


Looking up at oil pickup 1998 XJ8

Also I know that many automakers scammed customers with the 'lifetime' transmission fluid, but apparently some folks think that motor oil is also 'lifetime'


Gungy oil pan

Amazing that the engine has made it this far with such poor maintenance

I poured the oil over a very strong magnet and fortunately there was no metal shavings or powder.

On a side note, I am very pleased with how easy it is to work on this car. Compared to most modern vehicles this is a walk in the park.

Hope this helps others who may be seeing oil pressure issues with their cars.
Cheers
Ken

 

Well I spoke too soon.

I cleaned out the pickup and used air to blow out any debris, re-assembled the pickup, cleaned the pan, re-installed, topped up with oil....same symptoms. Still have good oil pressure at idle, but drops off as RPMs increase.

I cleaned a LOT of debris out of the pickup and pan, so I am worried that a small piece is blocking pickup somewhere else. I don't think its a drain-back problem as I can run the engine, shut down, and the dip stick will read full right away.

I do recall seeing a post somewhere that the 1998 XJ8 dipstick was not accurate and that you have to actually overfill it. Anyone know about this?

All that remains that I can think of is to pull the whole timing assembly and replace the oil pump itself.

Does anyone know of or have a link to an oil passage diagram for the V8?

cheers(s)
Ken

 

How are you reading oil pressure? In the absence of a gauge, is there an obd2 figure, or have you fitted a gauge?

 

Hi

I used a mechanical gauge to replace the sending unit. I can see the pressure change immediately in real time.

Cheers
Ken

 

MOVED from X300 to X308.

Graham

 

You might want to go ahead and do an oil change with a new filter just in case it’s clogged??

 

Yes, thanks.

That would be a less work lower cost option to check one more item off the list.

Filter is likely VERY dirty; see pics above...


Also Thanks, Graham for moving the post.

Cheers
Ken

 

Yes, that’s what prompted me to suggest an oil change in the first place. That is some serious gelified oil in that pan. Is this a recent acquisition? How many miles/kms are on it?

 

Hi A2B

Yep, a new filter fixed the issue!!

Bought about 6 months back, but all was OK until a recent road trip where I was rather 'spirited' in my driving.

Plan now is to run a bunch of detergent oils through the car and do several oil & filter changes in the near future.

Car has 190,000km and runs great, so I am glad this was not a terminal problem (so far)

FWIW I only paid $2k CDN, so I expected there would be some deferred maintenance issues.

Cheers
Ken

 

Glad to hear you got it resolved.

Seeing that yours is a 98’ and the previous owner couldn’t change the engine oil, you might want to get the main pressure regulating valve in the transmissions valve body replaced asap. And one of the best things to do when the engine is cold, wait until the idle RPM’s come down to about 900 *before* you move the gear lever out of park. This is about 15 seconds for where I live but, it might take you a lot longer up in Canada.

 

Hi A2B

I am pretty careful to go easy on the accelerator until everything is warm.

Where I live, Vancouver Island, is the "Canadian tropics'. We see about 2 snowy days a year, and the majority of the year is above freezing.

I did see some postings about the valve in ZF 5HP24. I was thinking of a rebuilt valve body just to be sure. Wouldn't mind sharper shifting as well.

Cheers
Ken

 

Just so I’m clear, it’s the initial shift out of park into reverse or drive (when the engine is cold) that’s harsh on these transmissions.

 

gotcha.

 

Hi Ken,

I don't know what oil detergent products are available in Vancouver, but one I currently use when needed is Rislone Engine Treatment. In the past, CD2 Oil Detergent was the best I had found, but it is no longer available in the U.S.

Your idea of using a detergent and doing several oil & filter changes over the next several months is a good. I might even do it every 500 miles for three or four changes.

Good work! Please keep us informed.

Cheers,

Don

 

Does it have a sending unit? I don’t think k it does, Only an oil pressure sender for the low pressure light.
Not detracting from your other lubrication woes, but the declining oil pressure reading might be a red herring.

 

I have used Rislone products and found them to be quite good. My dad recommended.
the product while I was a teenager, and they have always served me well. I remember a
Ford Maverick with a similar neglected engine where it helped a lot.