The vehicle is a 420SEL, 1986, engine 116.965. I have a loud clicking noise that's located in the front of the engine, around the number 1 cylinder, which a tech at the dealer thinks is being caused by a "rocker arm" or a "hydraulic lash compensator". In researching the forum archives, it seems that with this engine any valve train noise is most often coming from a worn "rocker arm".

Up to this point, I have removed the valve cover and checked the oilers for any clogging, and all checked okay. My first question is whether or not I stand to damage the cam shaft if I drive the car a little longer before fixing the problem?

My second question is whether or not the "special tool" (part number 117-589-06-23-00) is mandatory for checking the "preload dimension" (basic position) of the hydraulic lash compensator? I'm wondering is anyone has come up with an alternate way to perform this check.

Thank you for any response.

William