Evening all, out of ideas on a bad noise my Jag's making. It's a 2000 XJR with 160k miles on it.. and it recently (500 miles ago) had new tensioners/chains due to a failed lower tensioner.

Prior to that, it had a pronounced rattle at idle - which went away after a couple of seconds. I pulled the valve covers, noticed one of the primary chains was slack, and replaced the lot. The lower tensioner wasn't moving - it was like the oil wasn't building up enough pressure in it to tension the guide.

Anyway...

The rattle came back after a couple hundred miles - and it's *much* louder now. At cold start, it is LOUD.. and once the car's warm, it knocks at anything above 1900rpm. I grandma'd it home and haven't driven it since.

So far.. I've changed the oil (currently Mobil 1 10-40 synthetic) and changed the (oem) oil filter. I've also pulled the sump and checked the pickup tube. The pickup screen had a few metal flecks in it, and the sump itself had about half a cup of silvery sludge and lots of pieces of old chain guide in it - I know the original guides/tensioners were replaced in 08, but I'm pretty sure the oil pan had never actually been off before. I've also verified I genuinely have low oil pressure with a gauge - additionally, the idiot light goes off after 2-3 seconds when starting and doesn't come on when hot.

So.. where would you look next? As it's a crank-driven oil pump, I'd assume they're pretty reliable... I'd also assume 160k isn't a galactic mileage for an engine that (on the face of it) has been well cared for. Can the oil pumps somehow lose prime?

Any thoughts very much appreciated.. except for 'switch the engine'. I've already thought about that :/

 

The biggest issue we see as you describe is that many of the specified oil filters for these cars do not have a check valve in them. The oil leaks down into the crank case and needs a few seconds for pressure to return. Noise in the meantime.

Then there is That sorta defines the That signifies something much more serious . . . like a rod knock caused by a failed oil pump.

 

Have used OEM oil filters the entire time I've had the car.

Also forgot to note.. no evidence of oil leaks. No drips, no smoke, and level doesn't drop. It's currently right on 'max' when cold.

 

At 160,000 miles I would not spend too much on the engine. If everything else is good, find a nice one out of a wreck with a warranty. Not what you want to hear,
but it will likely save you $$$.

 

Kinda the route I'm thinking. It'll be a couple months before I can get it a replacement motor, but at least they're pretty available round here. I'll be doing it myself.

I found some videos in one of the 'rod knock?' threads; my noises are *identical*. I got maybe 20 miles of "warning" before the noise got ridiculously as loud as that - which was enough to get me home. I moved it again today, and it's still quiet as a mouse until its warm... but as soon as it's been running for five minutes or so, knock knock knock...

At least I can then pull mine apart to figure out what actually happened. It's not my only car, but my daily driver is now a 1967 Rover P6. Very nice, but going from 370bhp to 115bhp is definitely an eye-opener.