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A ticking noise for a few seconds after a cold start is common on R107 V8s. Most of the time it is the hydraulic valve lash compensators (lifters) filling with oil. If it continues after warm-up, or gets louder, it deserves a closer look.
Normal vs not
- Normal: a light tick for a few seconds after a cold start, especially after the car has sat for days, which fades as oil pressure builds.
- Not normal: ticking that lasts more than a minute, continues when warm, gets louder with rpm, or is a heavier knock.
How hydraulic lifters work
The M116 and M117 V8s use hydraulic valve lash compensators that adjust valve clearance automatically with oil pressure. When the engine sits, oil can drain from some compensators. At startup they make noise until they fill again. That is why the tick is often worse after long storage.
Oil causes
- Low oil level: check first.
- Wrong viscosity or old oil: thick oil when cold or thin, sheared oil when hot can both cause noise.
- Low oil pressure: see oil pressure.
- Sludge restricting oil passages, on neglected engines.
- Worn or sticking compensators.
Other sources of ticking
- Exhaust manifold leaks: a tick that fades as the manifold warms and seals.
- Injector noise: fuel injectors make a normal ticking sound; see fuel injectors.
- Timing chain or tensioner noise: a rattle at startup, especially on 380SLs, is more serious. See 380SL timing chain.
- Rocker arms or camshaft wear.
When to worry
- If the oil pressure gauge reads low.
- If the noise is a rattle rather than a tick.
- If the noise continues after warm-up.
- If the engine also runs badly.
Fixes
- Check the oil level and change the oil and filter with the correct grade.
- Drive the car regularly; long storage makes startup tick worse.
- If one compensator stays noisy, it may need replacing. Replacement requires removing the valve cover and camshaft-related parts; follow the factory manual.
- Fix any exhaust leaks at the manifold.
Quick answers
- Is startup tick harmful? Brief startup tick is usually harmless.
- Will thicker oil fix it? Not usually; use the oil grade recommended for your climate and engine.
- Can additives help? Some owners use flush additives, but results vary; a proper oil change is the safer first step.
- Does the M110 six have the same? The inline six uses a different valve adjustment design; check your manual.
