Timing Chain - Why is it so complicated?

[timbutjack]

Hi - I've signed up here to look for some advice.

I want to change the timing chain on my 1.4 TFSI 2009 A3 - it rattles slightly on cold start (first 10-20 seconds) I want to change it now before it does any damage.

So far I've bought a locking tool for this engine and I've bought a chain kit.

In the kit includes

Main Chain
2 sprockets
Crank sprocket (press on type)
Chain guides
Tensioner
Few other bits (new bolts etc)

Question is, I don't have the puller and press tool to change the crank sprocket, why on earth would the kit include the Sprocket but not the oil pump chain too? My reasoning is that if the OEM chain has slightly different tolerances to the aftermarket one then its not going to run properly.

Do I

A) leave the original sprocket on with the original oil pump chain and fit a new timing chain and tensioner (hoping that the aftermarket one lines up perfectly with the original sprocket)
B) change the sprocket so it lines up perfectly with the new timing chain but potentially not with the oil pump chain
C) just go to Audi and pay £500 for all the OEM parts + the press tool

Also, I'd like to change the chain cover at the same time to minimise the risk of oil leaks from the old warped cover. Does anywhere sell an aftermarket one? Again Audi quote around £500 for this part alone.

Thanks

 

[15audis3]

Any reason why you don't just change the tensioner for the latest version? The chain/guides etc don't necessarily need replacing for the rattle on startup.

 

[timbutjack]

I gather the chains stretch, so the tensioner alone might not be enough - however I suppose I could just change the tensioner and chain for the latest genuine Audi parts.