David:

W116 suspension is identical to the W126 and W123 front end except for parts size.

The part you are describing is the idler arm. Check for vertical play -- if you can move it up and down, you need new bushings.

Usual source of knocking/groaning on the W116 is a bad thrust (track) rod bushing on the body, followed by (yikes) bad mounts or bushings on the upper control arm or firewall (sway bar, which acts as the upper control arm mount).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!