Timing chain assumes a 2.0T petrol engine. Timing chain stretch and a faulty chain tensioner design are known problems with the early 2.0T petrol engine.
A couple of references:
B8/B8.5 Buyer's Guide and "Looking to buy" Question Thread (see the entire first post)
Timing chain stretch affects two things mainly: engine timing, of course, and timing tensioner extension. If the chain stretches enough, the tensioner extends too far and fails, which can cause major damage to the engine. This happened to a colleague of mine at a previous job. We had our timing chain and tensioner replaced as a preventive measure. --g
A couple of references:
B8/B8.5 Buyer's Guide and "Looking to buy" Question Thread (see the entire first post)
Results of measuring timing chain stretch via cam phaser adaptation. - Page 38
I promised results of before and after with the cam phaser adjustment measurement between a new chain and old one. At idle, you can see the difference here. My chain was stretched roughly 3/4 of a full link. Before http://i67.tinypic.com/2887cbb.png After http://i65.tinypic.com/wvoewo.png
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