KNOWN FAULTS · Mercedes-Benz

Known faults for the Mercedes-Benz SLC (R172).

2016–2020 · Petrol / Diesel

Sources are not verified in real time and no entry confirms that your car is affected.

3 known faults with sources

Engines: SLC 180 / 200 / 300 (M274) (Petrol)

M270/M274 chain, adjusters and thermostatTiming / leaks

Engine / equipment: M270 and M274 1.6/2.0 turbo petrol (A, B, CLA, GLA, C, E, GLC, SLC)
Period mentioned: 2012–2020
Symptoms: Chain rattle on cold starts; engine light with camshaft timing codes (for example P0016 or P001685); oil leaks at the camshaft adjusters; slow coolant loss.
Possible cause described: The hydraulic tensioner loses pressure overnight and the plastic guides wear, especially with long oil change intervals. The camshaft adjuster magnets leak oil (common between 65,000 and 110,000 km) and the plastic thermostat housing cracks.
Check for the garage: Listen to a cold start, read camshaft codes, look for oil on the adjuster magnets and coolant residue at the thermostat. Use Mercedes 229.5 oil.
Cost cited in the source: Chain and tensioner: approx. €320–1,650 (converted from dollars)A rough figure from the original database, not an up-to-date quote.

Mileage cited in the database: 65,000–110,000 km. This is not a maintenance interval and does not predict a failure.

Engines: SLC 180 / 200 / 300 (M274) (Petrol) · SLC 250 d (OM651) (Diesel) · SLC 43 AMG (3.0 V6) (Petrol)

Applies if: Only if fitted with the automatic gearbox described in the record.

9G-Tronic harsh shiftingAutomatic gearbox

Engine / equipment: 9G-Tronic automatic gearbox (725.0 and 725.1): C-Class W205 and W206, E W212 and W213, CLS, S W222 and W223, GLC, GLE, GLS, SL and SLC
Period mentioned: 2013–2026
Symptoms: Harsh or jerky shifts (especially 1st to 2nd and when cold), vibration, delayed shifts or limp mode; sometimes the gear will not engage from N to D. Codes P073E00 and P07B700.
Possible cause described: Mercedes acknowledges in a technical bulletin complaints of harsh shifts, shudder and limp mode with various causes. In the early years (2014–2016) it is usually software or adaptation rather than mechanical damage; in other cases the pressure sensor built into the gearbox control unit fails.
Check for the garage: Follow the Mercedes bulletin: reproduce the complaint, save the EEPROM, check the oil level, run the Xentry valve flush, update engine, gearbox and shift unit software and perform the standstill adaptation. If it persists, check the control unit.
Cost cited in the source: Software update and adaptation: the most common and cheapest fix; repairing or replacing the control unit costs considerably more (the sources give no comparable figures)A rough figure from the original database, not an up-to-date quote.

Engines: SLC 250 d (OM651) (Diesel)

Chain, injectors and coolant leaksTiming / injection

Engine / equipment: OM651 2.1/2.2 CDI (C 200/220/250 CDI, E 200/220/250, GLK, Vito, Sprinter)
Period mentioned: 2008 onwards
Symptoms: Chain rattle on a cold start; on early units, loud injector knocking; coolant loss from the plastic coolant manifold or the EGR cooler.
Possible cause described: Plastic chain guide and a hydraulic tensioner that loses pressure (the chain is at the rear). Early units used problematic piezo injectors that Mercedes replaced in a campaign.
Check for the garage: Listen to a cold start, check the dealer's injector campaign history and check the coolant level.
Cost cited in the source: Chain: approx. €1,500–3,000 (estimate)A rough figure from the original database, not an up-to-date quote.