After 100,000 miles my 2008 XJ8 has bad (noisy) variable valve timing again, as diagnosed by the local dealer during its 100,000 mi service (previously replaced around 60,000 mi with the timing chains and tensioners). I've been ignoring them but they are starting to sound really bad to the point that even my wife commented on the noise. I think I'll have to replace them just to stop being embarrassed, but what happens if I don't? Do they come apart, or break the timing chain, or ??
I have a hunch that you probably had only the tensioners replaced at 60,000 miles. Was it just the secondarys [uppers] or was it all four, there are two primaries as well [lowers]. Is the noise constant? The VVT noise can usually be confirmed by starting the car after it has set about an hour, WITHOUT touching the throttle. They are usually making the most noise at that time. If you goose the throttle about half way, that will force the system to engage the VVT's. That charges them with oil and they usually quiet down for a while. If you can confirm that, then it probably is the VVT's, which would mean going into the engine again. As yet I have never seen a VVT fail in a catastrophic manner, [though that doesn't mean it couldn't happen] they just make noise or in the worst case set faults [Check Engine Light] if they actually fail to adjust the cam timing when commanded.