My 1986 300E 5-speed with 191K miles has started making a worrisome noise. I would call it a loud rattle, from the front of the engine.

Not present when cold, but very apparent when warm.

No change if turn AC on.

Increases in tempo as RPM increases.

Does not seem to be coming from cam/valves. If had to guess, loudest in lower front passenger side of engine.

Oil level and pressure are normal. Using 20-50 for summer driving.

Sometimes will diminish if I let the clutch out.

I bought this car from the original owner. Regular maintenance, but no major engine work.

TIA for ideas.

Chuck