The Mercedes-Benz GLC has been one of the most popular premium mid-size SUVs in Australia since it replaced the GLK in 2015. The X253 generation went through a significant facelift for the 2020 model year, bringing the new M264 2.0-litre turbocharged petrol (replacing the earlier M274), a 48V EQ Boost mild-hybrid system, the updated 9G-TRONIC nine-speed automatic, and MBUX infotainment. Diesel variants with the OM654 engine and 4MATIC all-wheel drive were also sold locally. The GLC is refined, well-equipped, and holds its value well — but it punishes neglect expensively, and the facelifted car's mild-hybrid architecture adds complexity that independent workshops can struggle to diagnose without Mercedes' XENTRY tooling.
M264 engine: cylinder head wear and oil leaks
The M264 petrol in the 2020 facelift is the engine that warrants the most due diligence. Two issues have emerged in owner communities worldwide, including Australian threads on MBWorld and GLC forums.
Cylinder head valve guide failure
The M264 has been linked to premature softening of the cylinder head valve stem guides, allowing excessive valve movement that eventually damages the valve seats. Symptoms include misfires, rough running, and increasing oil consumption — often appearing after the factory warranty expires. Cylinder head repairs are major work, likely running into several thousand dollars at a franchised dealer in Australia. Mercedes-Benz has acknowledged a similar defect in the related M260 engine (A-Class, B-Class) with extended warranty coverage, but no comparable program for M264 owners has been publicly announced. A pre-purchase inspection from a Mercedes specialist should include checking for any stored misfire codes and evidence of elevated oil use.
Timing cover and valve cover oil leaks
Both the M264 and the earlier M274 develop oil seepage from the front timing cover and valve cover as they age. Oil often wicks from camshaft adjuster solenoids seated in the timing cover, and because it migrates downward it is easily misidentified. A UV dye trace or clean-and-inspect approach gives an accurate diagnosis. Reseal work at an independent Mercedes specialist typically costs $600–$1,500 depending on access and severity.
48V EQ Boost mild-hybrid: electrical gremlins
From the 2020 facelift, Australian GLC petrol models carried the 48V EQ Boost system — a belt-driven integrated starter-generator with a lithium-ion 48V pack alongside the standard 12V battery. Internationally, this system generated a significant number of owner complaints; NHTSA opened an investigation into 48V ground-connection faults on 2021–2024 production. Reported symptoms include the car failing to start, unexpected shutdowns while driving, and persistent warning lamps. The 12V and 48V batteries interact — a weakening 12V can drain the 48V pack. Fault diagnosis requires the XENTRY dealer tool. Budget $1,000–$3,500+ for EQ Boost component repairs; some cases are resolved by a software update, while others need the 48V battery replaced.
9G-TRONIC: low-speed shudder and adaptation drift
The 9G-TRONIC is generally smooth but some Australian owners report jerky or hesitant shifts in stop-start traffic. Common causes are:
- Torque converter shudder at low speed (noticeable around 20–40 km/h under light throttle)
- Adaptation drift — learned clutch pressures falling out of spec, causing abrupt changes
- Degraded or overdue ATF — many used GLCs have never had the fluid changed
A XENTRY Standstill Adaptation procedure at the dealer often resolves the jerkiness without parts. An ATF and filter service is recommended every 60,000–80,000 km and typically costs $300–$600 at an independent specialist.
COMAND and MBUX infotainment: black screens and freezes
Pre-facelift GLC models ran COMAND Online; 2020+ cars use MBUX. Both generations have attracted forum reports of screen blackouts, system freezes, and spontaneous reboots. On COMAND-equipped cars a blank screen is frequently traced back to a weak 12V battery — worth ruling out before assuming the head unit has failed. MBUX glitches are more often software-related and many resolve with a dealer update. Persistent issues sometimes clear after disconnecting the 12V battery for 15 minutes to force a full system reset. Hardware head unit replacement can reach $2,000–$4,000+ at a dealer, so always exhaust the software path first. Some owners also report COMAND or MBUX faults cascading into the electronic park brake, washer jets, and park-assist systems.
Panoramic sunroof: blocked drains and rattles
The optional panoramic roof is a recurring complaint area. Blocked drainage tubes — routed through the A- and C-pillars — are the main culprit: when clogged with debris, water backs up and appears as wet footwells, a damp headliner, or moisture in the boot. The fix is straightforward (compressed air or a drain-clearing cable) but should be checked at every service if the car is parked under trees. Rattle from the sunroof glass or track mechanism is also reported, usually resolved by lubricating the track and seals. Seal degradation on the fixed rear panel is a separate slow-leak source; seal replacement typically costs $300–$800 at a workshop.
Brake wear: rear pads consumed early
Premature rear brake pad wear is a well-documented GLC issue discussed on Australian forums including Whirlpool. On models fitted with adaptive cruise control (ACC), the system preferentially uses the rear brakes to manage speed, significantly accelerating rear pad consumption. Owners have reported needing rear pad replacement as early as 24,000–30,000 km. A rear pad-and-rotor service at a franchised dealer can cost $700–$1,200, with some owners reporting quotes above $2,000 for a full four-wheel brake service. An independent Mercedes specialist and ADR-compliant aftermarket pads are sensible cost-management options.
Servicing costs
Mercedes-Benz Australia offers capped-price servicing during the warranty period, but costs rise once a GLC moves into private hands or the window closes. Dealer Service A typically runs $500–$700; Service B can reach $1,000–$2,000+. Independent specialists with XENTRY access can cut routine service costs by 20–40%. Also budget for brake consumables, OEM-spec tyres on larger wheels, and the potential cost of ATF or EQ Boost system service on higher-kilometre examples.
Recalls & safety
The X253 GLC has been subject to multiple official recalls in Australia. Verified recalls include:
- Sunroof panel detachment (RC2885, 2021): On 2015–2019 GLC models with panoramic sunroofs, the panel between the windscreen and sunroof may not have been correctly re-bonded during a prior service, potentially detaching at speed.
- Steering control unit wiring (RC2841, 2021): Affecting GLC vehicles sold in Australia between February and July 2020 — damaged wiring in the steering control unit could allow moisture ingress and cause loss of electric power steering.
- Seatbelt buckle (RC27650, 2020): Front seatbelt buckle housings on 2018–2019 build vehicles may have been incorrectly manufactured, causing a fastened belt to read as unfastened and disabling tensioners in a collision.
- Rear seat backrest latch (RC2797, 2020): On GLC vehicles sold March–June 2020, the left rear seat backrest lock could fail if struck by cargo in a collision.
- eCall software and side crash sensor faults (2021): Multiple campaigns affecting 2018–2020 GLC models covering deactivated emergency-call functions and side crash sensor connectors that could delay airbag deployment.
Carify has recall data mapped for the 2020 Mercedes-Benz GLC — check there for year-specific detail. You can also browse the full recalls landing page or the all-models hub.
Buying a used Mercedes-Benz GLC? What to check
- Engine health: Look for oil spots around the timing cover and valve cover. On M264 cars (2020+), ask about any misfire history and check for relevant dealer repair records.
- 48V system: On facelifted models, request a XENTRY health scan to surface any stored EQ Boost fault codes before purchase.
- Transmission: Test drive in stop-start traffic. Shudder or jerky downshifts under 40 km/h warrant investigation; ask when ATF was last serviced.
- Infotainment: Cycle through all MBUX or COMAND functions during the test drive and confirm the screen holds a stable image.
- Sunroof drains: Pour water into each drain corner and confirm it exits beneath the car. Check the headliner for staining.
- Rear brakes: Check remaining pad thickness — under 3mm at low kilometres signals ACC-related consumption and an immediate expense.
- Recall status: Confirm the sunroof bonding (RC2885) and steering unit (RC2841) recalls have been completed — both are safety-critical.
- Finance and write-off history: Run a PPSR check to confirm the vehicle is not encumbered, stolen, or a written-off rebuild.
The verdict
The Mercedes-Benz GLC X253 is an appealing used buy — refined, well-equipped, and strong on resale. Pre-facelift models (2015–2019, M274 engine) have a relatively settled reliability record for the segment, with sunroof drainage and brake wear as the main ongoing management tasks. The facelifted 2020–2022 models with the M264 and 48V EQ Boost system are more capable but carry a higher risk profile, particularly around the cylinder head and mild-hybrid electrics. Budget realistically for servicing, inspect thoroughly, verify all open recalls are closed, and get a pre-purchase inspection from an independent Mercedes specialist. Do that preparation, and the GLC can be a rewarding long-term ownership proposition.