HLC failure? Occasional loud tapping
This is on a 1989 560 SEL with 106k miles.
I get an occasional loud tapping from the driver's side valve train. There are two things I wonder about:
1. When I hear the tapping, I turn off the engine (warm at this point), and immidiately restart it. Tapping is gone.
2. I just did the oiler tubes, and had to remove the timing sprocket on that side because I replaced the inner rail. I'm just struck by the coincidence of having opened up that valve train a couple of weeks ago, and now developing a tap. Is there anything I could have done wrong? I did check for cleanliness before closing her up.
If I had blocked the oil channels somehow, I could be hearing a dry lobe hitting the rocker. However, why would it stop and be gone if I just turned off the car and restarted it?
The binary nature of this problem (it's either there or it isn't) makes me suspect it's a HLC after all, and an oil treatment might be a first step rather than opening her up again. If I messed up, I need to remove the fuel lines etc and go right back in to see what's going on. At which point I might as well buy a HLC, the adjustment tool, etc. just in case it's the HLC after all.
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)