I have a 1995 318i , automatic, 127,000 kms. Last few weeks there is a chain rattle noise occuring from engine area, when car idles from cold start. Once car is revved up, the rattle goes away. I am thinking the timing chain tensioner need replacing. Previous posts indicate this is a very easy, and inexpensive job. I have a Bentley manual, and I will be following it when changing the part. But, I was wondering if the timing chain can be observered with cover off, and engine running. Probably NOT !! So, when I remove the cover, and inspect the chain, how will I know if the tensioner needs to be replaced? Should there be ANY slack in the chain? Anything else I should be looking for?
Thanks

Is it REALLY this complicated ??

I quickly looked through the Bentley manual, and contrary to some posts, this is a very involved repair. Is it really necessary to drain the engine oil, drain the coolant, remove the fan and shroud, disconnect the hoses from thermostat housing?? Every post I've seen suggests this is a 10-15 minute job....am I missing something here?
Your advice is appreciated
Thanks