Gang,

It's been a long time since I've had time to read the boards, but I'm back for advice. I have a sharp clicking noise on cold startup on my S52 M coupe, now with approx 125k miles. The click's cadence is about twice per second and it goes away within about 90 seconds. The sound seems to emanate from the top front of the engine, about where the cam-to-cam chain would be.

After doing some research on-line, I could simply be facing a tensioner / guiderail problem at the top, it could be due to the main tensioner, the crankshaft-to-camshaft chain could be due for replacement or it could be the VANOS unit going bad. I lean toward preventative maintenance, so I'm thinking I should start by replacing both tensioners and I'm strongly considering replacing the VANOS unit as well.

1) If I don't replace the VANOS unit right now, does anyone know if I will be able to replace the upper tensioner and guide without undue difficulty?

2) If I *do* replace the VANOS, I'm inclined to buy / rent the tools to do it myself. Randy or Ron, do you believe this is work that a reasonably detail-oriented person could perform? As a reference, I do my own clutch replacements, installed an M50 manifold and OBDII adapter from Eurosport, routinely do my own brake work (rotors, lines, etc.), removed and replaced my differential and generally feel comfortable tearing into the car. If this requires a PHD in thermodynamics I'll pass it along to a local mechanic, but I'd prefer to get into it myself and inspect everything exposed by the work. And since it's time to do another water pump replacement - and finally install the new radiator I've had for the past 18 months - now may be a good time to knock everything out.

2a) If I do the work myself and need to rent any tools, would anyone care to recommend a resource? Koala is the resource I've read about already. That highly-sensitive torque driver that Ron and Randy discussed looks like an *ideal* rental.

Thanks in advance,

Mike