Today after I finished all my appointments and the service center closed I pulled my car into the shop and began the process of adjusting the valves in my 300d for the first time.

The service interval for valve adjustment is 15,000 miles and I’ve had the car for longer than that but I have not had access to a garage for the last 8 months until I started this job. Thankfully one of the master techs let me take the key to his box and use his tools to supplement my own, otherwise I would have struggled much more. I began by disconnecting the battery and removing the fan shroud and fan from the front of the engine. getting the fan off required an interesting arrangement of 2 10mm wrenches, I had to remove it so I could get a 27mm deep socket on my crank pulley bolt in order to rotate the engine by hand.

This is $300 worth of ratchet and socket

I then had to disconnect the mess of a throttle linkage and remove the valve cover.


To adjust the valves you rotate the engine until the cam lobe for that valve is pointing straight up and then you insert a feeler gauge between the base of the cam and the rocker arm (.004 for the intake and .012 for the exhaust) to adjust the clearance you must loosen the bottom lock nut on top of the valve spring and then hold it in place while you adjust the top nut until it hits the feeler gauge and then tighten the lock but.


This is pretty difficult by yourself but I got the hang of it after the 4th or 5th valve. Turns out even though it was pretty far past the service interval most of the clearances were within an acceptable range except the lock nut for the exhaust valve on cylinder 5 was finger loose and incredibly out of spec, the last person to adjust the valves must have failed to tighten the lock nut and the adjusting nut backed all the way out. After I got everything back together the engine started and ran noticeably better but when I was wrestling with the valve cover I must have accidentally unplugged the line to the vacuum shutoff valve because the engine did not turn off when I turned the key and I had to use the manual shutoff. Unfortunately I couldn’t stay much longer so tomorrow I’ll have to go back and find the disconnected vacuum line and then detail the engine bay because I got oil everywhere