Hi All.

I have a 1999 XJ8 4.0

Love my Jags, had loads but this is my first V8.

When in normal use there is a knocking that sounds like its coming from the left bank / bottom half of the engine.
I don't use the car very often, so when I took it for its MOT, the emissions were high. I took it for a good blast (about 2 miles of high revs and hard acceleration) and when I got back to the MOT station the engine was nice and hot (not above normal on the temp gauge) and the knocking had stopped. As the engine cooled whilst ticking over it returned within 10 min.
Is it a timing issue? it doesn't seem to make the noise under load, only when you let off the gas is it louder.
Is it lack of oil and a good hard run forces the oil through?
I have changed the oil and filter but it made no difference.
Seeing as the noise goes after a good run, does that mean there is no permanent damage at this point?

All comments and help is greatly received.

 

You've posted in the wrong forum. Ask an administrator to move your post to the X308 forum where you'll no doubt get some good advice.

FWIW, these engines suffer from faulty upper camchain tensioners that are best replace as soon as possible, if not before. Having said that, your noise source doesn't sound like it is those. but it could be the lower tensioner.

 

This might be a problem with the VVT solenoid or the VVT unit itself. These units are oil pressure activated, so oil temp and pressure affects them.