Lower timing tensioner didn't fix it, what else could it be?
 

My 1993 325i (M50TU, 102k/mi) had a pretty distinct rattle from the timing chain/VANOS area. The lower tensioner was definitely tired, so it's good I replaced it, but the rattle is still there.
I probed around with a stethoscope and found that it is loudest near the VANOS unit, but the sound is a distinct chain-slapping-around sound that to me would be indicative of a failing upper tensioner. Is there any easy way to test the VANOS unit? What are the odds of a failing VANOS compared with a failing tensioner (which, if I replace the VANOS, I would be replacing anyway since the engine is open).

Also, I have read about people simply changing to a slightly heavier oil and having the problems go away. Thoughts?

Thanks.

I always find the heavy oil fixes suspect.

Your EXACT problem has been discussed and repaired in this forum in the last 6 months or so. If you don't find it let me know.

Yeah, I always figured that heavy oil simply masks the problem.

As for the fix, I searched for anything pertaining to my issue and came up dry...

Searching for "chain tensioner" I got these three plus a BUNCH more:

http://forums.pelicanparts.com/showthread.php?s=&threadid=330860&highlight=chain+ tensioner
http://forums.pelicanparts.com/showthread.php?s=&threadid=315092&highlight=upper+ chain
http://forums.pelicanparts.com/showthread.php?s=&threadid=314725&highlight=upper+ chain

In the first one I mention the second two. In the last one jeff325525 replaced the tensioner parts for his Upper tensioner.

My car is not as loud and the tapping is more metallic than jeff325525. My neighbor diagnosed the sound as rockers, until I explained to him that it was DHOC and showed him that the sound was coming from the chain cover.

It sounds like an upper tensioner didn't help, but replacing some VANOS parts did...

I will try to record the sound today and put it on my website to aid in diagnosis.

Thanks for all the help. :)

Okay, I went back and had a re-listen. My VANOS does sound like a (much quieter) diesel. I have stock cams, but it still sounds very much like jeff325525's car.

It would appear that I need to replace the parts mentioned in the other topic. Is this a simple procedure? Upon removing the VANOS unit, do I need to lock the cams or follow any other special procedure?

Thanks again.