1993 400E lifter tap
 

1. Proud new owner of a 1993 400E with extensive service history. Car has an intermittent lifter tap. Changed oil with 5w-40 syn and added MOA which seemed to help as it is now sporadic. Should I be concerned?
2. What engine temp do the accessory fans turn on at? I know they work with the AC on.
3. Great site . :)

Isolate errant lifter and check preload.

The lifters in those engines are super hard metal and even ones left tapping for a long time never show any wear on the cam or lifter. You should fix it but you are not in danger of engine damage in the mean time.

I know that Mobil 1 synthetic oils have a reputation for quieting noisy lifters, usually takes several thousand miles of driving.