T5 rattle on startup
 

2008 Volvo C30 T5 with 145k miles.
Loud noise on cold startup that sounds like a rattly dry bearing that morphs in to sounding like diesel knock.
Fades out after a few seconds.
Appears to be coming from the area of the exhaust camshaft a few centimetres inboard of the drive pulley.
Is not a loose exhaust stud (I've been down this route having found a YouTube video of what appeared to be the same problem)

This leads me to suspect VVT - in which case, solenoid or something else?
Agree?

Don't know much about the T5 engines, but cambelt tensioner can sound like this with other engines...

Thanks, kmb, but it is not the tensioner; both the wrong location and the tensioner was replaced along with the belt at the correct service interval and the noise persisted either side of change.

Research online indicates that if the VVT pulley is failing, it tends to go quiet when then VVT solenoid electrical feed is unplugged. Mine doesn't; the rattle is the same both with the solenoid connected and disconnected.

What matters is that the engine has stood still and gone cold. If still warm, there is no rattle.

Careful listening with a stethoscope indicates that the rattle is coming from about four inches along the exhaust cam from the pulley end.

My conclusion is a lazy hydraulic lifter bleeding down and then needing to be pumped up again.

Other thoughts?

I have put a video here.

The engine is started ten seconds in.

Ignore the water; I'd just carefully degreased and then rinsed the cylinder head whilst I had the plastic cover off.

Are you sure that's not an exhaust leak from the manifold bolts? this can very often be confused as a 'tick' sound.

I noticed as the engine started there might have been a small screech which most report as the manifold leaking.

The T5 valve train is normally quiet.

Thanks for the suggestion, Welton, but per my original post this was the first avenue explored. My local garage assures me that all the bolts are tight. I do wonder if it's worth removing the manifold and fitting a new gasket anyway - but this is going to be in 16 months' time as I've just been posted abroad with my work, brought my family with me, and parked up two cars and two motorcycles for our return! They'll each get occasional use, but troubleshooting the T5 startup rattle will now have to wait!

Sounds like a sticky Hydraulic valve lifter to me.
when was the last oil change and what oil was used ?.
The motor factors do sell oil treatment to clean out sticky lifters then give it a oil change with quality oil.

Closing this thread four and a half years later.

The 'rattle' was indeed a blowing exhaust manifold gasket that leaked on cold startup until temperature caused expansion that closed the gap.

It gradually got worse and worse, eventually taking a good five seconds to go quiet. On replacing the turbo this week and fitting a new exhaust manifold gasket, the 'rattle' is gone.