I have an 05 4.2 litre XK8 that at 35K miles began making a clatter for the first two seconds of a cold start. Sounds like a dry start with no oil. It is just through that initial rpm jump at start up when the oil is cold. I took it in to be checked and they diagnosed a defective tensioner. Covered under warranty. Also got all the other tensioners and both timing chains covered and replaced. They reassembled and that cold start clatter is still there. Only on the drivers side of the engine and again only for the first two seconds of a cold start. The sound appears to be equal from front to rear but is on the left bank. They tore it down again and looked into the oil sump and saw some shimmer. There turned out to be more metallic shavings than what they like to see. The metals were non magnetic or aluminum. They are scratching their heads at this point trying to determine what else it could be. Maybe the bad tensioner is as a result of something else? Maybe there is a slight oil blockage somewhere and it clears when the psi comes up? Input would be much appreciated. BTW, I have been more than religious about oil changes. Full synthetic every 3-5K since new. They said everything internally looked like brand new. Thanks in advance!

JimC64 - Dan you have an XK8 not a KX8.....I've edited both your title and post to reflect this and hopefully get you the best help possible!

 

'There turned out to be more metallic shavings than what they like to see'

Wonder at what point their comfort zone peaks for metallic shavings swimming around in the oil. I tend more towards a zero tolerance approach.

Regular oil changes and tensioner work rechecked. Identified as one bank and top end so the following possibilities come to mind:

1. tensioner oil jet which lubricates the chain is blocked
2. camshaft bearings / caps worn
3. V V T
4. valve lifters
5. valve shims
6. valve stem seals damaged / missing

From the list of work already done, it sounds as if you're fortunately covered for whatever may be needed.

 

Talked to the shop again this morning. Apparently the VVT actuator and Carriers need to be replaced. He said something about something being bolted on at maybe a millimeter out of alignment causing wear and it sounds like I need two of each...

 

Startup clatter on a car with non-hydraulic lifters is a concern. I suggest replacing the oil filter with one containing a good anti-drainback valve in it to start with. If the tensioners are bad, this could also do it, altough you say they are okay. The primary chain tensioners are hydraulic, so maybe they are sticking or have not been set up right. There is a procedure for installing them correctly to prevent this problem. My guess is problems with the primary chain tensioner installation.

 

The VVT on one side had wear on the spindle causing the oil to drain back. Replaced both VVT's and carriers as well as tensioners and chains. One tensioner on the side that was losing the oil died. Noise is gone. $6700. Apparently the slight alignment was due to improper machining of the parts for the first year 4.2 If you find one with this cold start noise be prepared to spend big bucks. The car only had 45K but we decided to replace the chains anyway.

 

I would use a different place when the warranty runs out.
Questionable diagnostics? If in doubt throw lots of expensive parts at it?
Go elsewhere!
I pity the warranty company.

 

This is the first I have heard of this, wonder why it has taken so long to show up? Could it be that it was just this one? If I were the shop, I would only replace the damaged part unless it was clear that it, too, was made wrong. There is no reason to believe the other one was bad too. I also see no need to change tensioners and chains on the 4.2, they don't have a longevity issue that I'm aware of. Glad you got it fixed though, you were saved by the warranty.