That Knocking Sound in Your Classic Mercedes: What It Could Mean (and When to Worry)

A 1986 Mercedes 560SL owner recently posted about a puzzling engine knock that had his trusted shop stumped. The valve covers were off, timing chain and guides checked—all looked fine. Oil changes every six months with Castrol 20W-50, fresh radiator flush, new belts. The car runs strong otherwise. Sound familiar?

For owners of older Mercedes-Benz models—or any high-mileage European or Japanese car—a knock that persists after basic checks often points to deeper wear. In the M117 V8, common culprits include piston slap, a worn camshaft lobe, or even a failing harmonic balancer. Sometimes it’s an exhaust leak or a loose accessory.

The key is ruling out the serious stuff before it turns into a big bill.

What this means for you: If you drive a Mercedes, BMW, Audi, Porsche, VW, Volvo, Jaguar, Lexus, Toyota, or Honda (including hybrids), don’t ignore a new knock. A quick listen from a seasoned technician can save you thousands. At our family-run shop in Boca Raton, we’ve been diagnosing these sounds since 1989.

We’ll check the timing components, oil pressure, and listen with a stethoscope—no guesswork.

If your car is making a noise that worries you, bring it by. We’ll give you an honest answer and a clear plan. No pressure, just experience.