Mercedes-Benz

S63 AMG W221 (M156) inspection checklist

2007-2010 · 4 things to check before you buy, taken from this car's known problems.

This car

highCylinder head bolt failure (early M156)

Look for: The torque-to-yield head bolts on early 6.2L M156 engines can stretch and snap, usually at the rear of the engine; one failure overloads the others. Coolant and oil can then enter the combustion chamber, and in severe cases the engine is destroyed. Warning signs are repeated low coolant, high oil level, a check engine light and white exhaust smoke. Mercedes bulletin LI01.30-P-051567 (April 2011) describes the repair as removing the heads, measuring piston deck height and replacing the head bolts and hydraulic tappets, and the rod, piston and bearings if deck height is out of spec.

If you find it: Ask for invoices showing the head bolts and tappets were replaced to the bulletin. If there is no proof, treat it as a pending repair: get a specialist inspection (coolant pressure test, oil/coolant check) and negotiate accordingly.

Any (age-related, engines built up to about early 2010)

highActive Body Control (ABC) suspension

Look for: W221 cars with ABC had an Australian recall for the front strut ball joint (see Recalls) and are prone to leaking air bellows/hydraulic components with age; a UK guide advises checking ride height at every corner, since leaks overwork the pump and let the car sink. Owner-reported: warning lights and a lowered corner are the usual signs.

If you find it: Check ride height on all four corners after the car has stood overnight, scan for ABC faults, and confirm both recalls were done. Budget for strut and pump work.

Any

mediumCamshaft adjuster rattle and camshaft/lifter wear

Look for: The M156 is known for a rattle from the intake camshaft adjusters on a cold start, and for soft camshaft lobe and lifter wear. Mercedes acknowledged lifter/cam wear in service bulletin S-B 05.20/20b (2009) per an Australian guide. Overseas guides also list the camshaft adjuster solenoids as a common failure.

If you find it: Listen on a cold start. Repair is adjusters/solenoids, and cams and lifters if worn, done at the same time as head work if the heads are already off.

Cold-start rattle from about 100,000 miles (160,000km) in a UK guide (unverified)

medium7G-Tronic shift quality (valve body / conductor plate)

Look for: A UK guide says shifts were not always smooth on pre-facelift cars, linked to the valve body and conductor plate electronics of the 7G-Tronic.

If you find it: Test cold and hot, including kickdown and manual paddle shifts. Repair is a conductor plate or valve body service at a transmission specialist.

Any

2 minor things (low severity)

lowOil leaks and breather faults

Look for: UK guide: valve cover, camshaft solenoid cover and oil filter housing gaskets leak, the crankcase breather valve diaphragm and hose deteriorate, and the magnesium intake manifold and idler pulley can fail.

If you find it: Look for seepage around the valley and filter housing, and check for misfires (coils and ignition module are common causes).

Age-related

lowParking brake switch and small electrical faults

Look for: Owner-reported (Australian and UK guides): a faulty parking brake switch triggers a dash warning and brake failure message; intermittent A/C from a fan/blower fault and sunroof wind noise from a failed seal also appear, plus control-module electrical faults generally.

If you find it: Check every warning light, A/C and sunroof operation on test drive. Brake discs and pads are large and costly, so inspect them.

Any

From FlamingCars' Mercedes-Benz S63 AMG guide. It's a checklist of known problems, not a replacement for a professional pre-purchase inspection. Your ticks are kept in this browser only.