97 E420 119 ENGINES ARE NOTORIOUS FOR OILER TUBES
BLOWING OUT THE LITTLE PLUG CAUSING A TICKING NOISE.
I WOULD REMOVE BOTH VALVE COVERS.
AND YOU WILL SEE THE BLACK PLASTIC OILER TUBES.
FEEL FOR THE PLUG AT THE BOTTOM. THE ONE THAT IS MISSING
THE PLUG IS THE ONE THATS MAKING THE TICK NOISE.
I RECOMMEND REPLACING ALL OF THEM.
SOMTIMES YOU CAN FIND THE PIECE THAT CAME OUT OTHER
TIMES YOU CAN FIND IT IN THE SUB OIL PAN.
GOODLUCK