Touareg: 2004 V8
Join Date: Oct 2014
Second Vehicle: Still looking
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Thanks very much for such a quick reply. I guess I should have known better, it definitely makes sense. Unfortunately, that means that what was an exploratory inspection of the cam chain tensioner is going to turn into something very expensive.
For now, I have made a temporary repair by re-assembling the two halves of the broken bearing cap over the camshaft and then adding a piece of 1/2" x 1/8" steel over the top that I drilled matching holes into. This now clamps the top of the cap down and locks it solid. Hopefully that combined with the four good caps will hold it for a while. It seems to run fine for now. I'll just be gentle with it.
The original reason for the inspection was a rattling noise coming from the bottom of the passenger side bank of cylinders. It sounds like it's coming from the front of the cylinder head (just under the camshaft position sensor), but is constant (not intermittent as if it were one cam or one valve). It sounds just like a chain being dragged over a bar (or a wrecked roller bearing). From reading all of the threads and posts, it just seemed like the cam chain tensioner, but it definitely isn't. There is no wear on the guides and I ran the engine with the cam cover off and the tensioner was quiet and operating normally. Also, the tensioner on the other side occasionally does that at startup, but I know this is "normal" for this engine. I also replaced the timing belt a couple of months ago, but this made no difference either. The only way I stopped it was by moving the timing belt one notch advanced on the belt. When I did that, the tensioner tried to adjust for the advance and the noise completely stopped (hence why I thought it had to be the cam chain tensioner). It didn't adjust enough and it threw a code and the engine was a little rough, so I had to adjust it back. I've looked at the pulleys and bearings on the timing loop, but it's not those either.
I am running out of ideas and wonder if you'd ever heard anything like this before from this engine. The engine has 128,000 miles on it.
Thanks very much for any help you can give me.