^ thanks dopedpanda for that info - it gave me the motivation to try this.....
I think we might be onto something here....?
After reading this thread:
http://www.vwwatercooled.com.au/forums/f112/mk-vi-gti-noise-upon-start-up-cold-weather-74027.html
I started looking into this camshaft adjuster magnet as a possible culprit of the noise im still getting on startup (when engine is cold/cool).
Firstly, VW have revised the part so generally a revised part means that the original part had a higher than expected failure rate and required the engineers to re-think the design of that part.
With my car being a late 2009 built GTI, i have the old version camshaft adjuster magnet (metal body and silver in colour).
The new (revised) part has a black plastic body, so its easy to see whether yours is the original or the revised part.
Revised part:
http://www.ecstuning.com/Volkswagen-Golf_V--2.0T/Search/SiteSearch/06L109259A/ES2766014/
Original part:
After reading the thread above, i decided to remove this camshaft adjuster to take a better look and to see if there was any way to clean it out etc so that it would work correctly again. Im happy to buy the revised part from ECS Tuning, but wanted to try fixing the original one.
Once i had removed the part, i noticed that the "piston" that protrudes from the part was quite hard to move in/out of the body of the part. I wondered if some brake cleaner and degreaser might help loosen this up? So i sprayed both products into the little hole you can see in the picture below and within a short space of time, the "piston" was moving in/out of the body with much more ease.
I sprayed some more cleaner in there and let it sit for a good 5 mins before letting it drain out and cleaning it all up.
I put it back onto the car and connected it back up. I took out VCDS and made the camshaft adjuster magnet pulse in and out about 30-40 times.
Started the car up (1st start in a week) and no rattle. Not sure at this early stage whether this cleaning process has given this part a new lease on life or whether this will be short lived and the engine will be rattling on cold starts again next week....time will tell.
One thing is for sure, if you shake/rattle this camshaft adjuster magnet it makes the exact same sound that my engine does on cold starts.
Best part is that it only takes 5 mins to remove this part to inspect/clean it.
Piston retracted:
(you can also see the small rectangular shaped hole where i sprayed my cleaner to reach the moving parts inside):
Piston extended:
Showing engine with part removed: