ExhaustHigh
DPF, EGR and AdBlue faults on 2.1 and 2.0 diesels
- Typically appears
- 70,000+ miles
- What to inspect
- Check AdBlue countdown and warning history
2015–2023 Mercedes-Benz GLC · common problems & known faults
A mid-size premium SUV with strong family demand. Diesel emissions hardware and optional air suspension lead the inspection.
Compiled & reviewed by the VehicleFaults Research Team · last reviewed August 2026
Quick answer
The most commonly reported faults on the 2015–2023 Mercedes-Benz GLC are DPF, EGR and AdBlue faults on 2.1 and 2.0 diesels, Air Body Control leaks on optioned cars and Sharp metallic rattling noise from the rear of the engine bay on cold start indicating timing chain stretch (OM651 2.1L diesels). 3 of the documented issues are rated high severity · inspect these first. Full inspection points, onset mileage and what to check are listed below.
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Build the inspection planReliability snapshot
Based on the documented faults on this page for the Mercedes-Benz GLC.
4.6/ 10
- Critical
- 0
- High
- 3
- Medium
- 3
- Low
- 2
Guidance only · reflects reported patterns, not a specific car's condition.
Known faults to check
SuspensionHigh
Air Body Control leaks on optioned cars
- Typically appears
- 70,000+ miles
- What to inspect
- Check overnight ride height and cycle drive modes
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Build the inspection planTransmissionMedium
9G-Tronic harsh shifts without fluid servicing
- Typically appears
- 80,000+ miles
- What to inspect
- Ask for gearbox oil evidence and test kickdown
ElectricalMedium
COMAND, camera and parking sensor faults
- Typically appears
- Age-related
- What to inspect
- Test all cameras and sensors, including the 360 system
SteeringMedium
Severe juddering or 'crabbing' sensation from the front tyres on full lock.
- Typically appears
- All mileages (worse in cold weather)
- What to inspect
- Apply full steering lock and drive slowly in a tight circle on a cold, damp forecourt to feel for front tyre skipping.
EngineHigh
Sharp metallic rattling noise from the rear of the engine bay on cold start indicating timing chain stretch (OM651 2.1L diesels).
- Typically appears
- 70,000-100,000 miles
- What to inspect
- Open the bonnet, stand near the bulkhead, and have a colleague perform a cold start. Listen for a chain rattle lasting 3-5 seconds.
BrakesLow
Loud squealing under light braking and heavily lipped front brake discs due to the vehicle's heavy kerb weight.
- Typically appears
- 20,000-30,000 miles
- What to inspect
- Run a fingernail over the outer edge of the front brake discs to check for a pronounced lip, and listen for squeal during a low-speed brake test.
InteriorLow
Excessive creaking and cracking noises from the gloss black centre console and dashboard trim.
- Typically appears
- 30,000-50,000 miles
- What to inspect
- Firmly press the sides of the centre console and the infotainment screen surround to check for loose or noisy plastic clips.
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Build my inspection planFrequently asked questions
Is the GLC a safe stock choice?
Yes with history. It has broad appeal and holds value better than most rivals in its class.
What is the big-ticket risk?
Air suspension on optioned cars, followed by emissions hardware on high-mileage diesels.
Which engine sells best?
The 220d. It matches what UK family buyers expect for running costs and towing.
Does the 4MATIC all-wheel-drive system require specific maintenance?
Yes, the transfer case fluid must be changed alongside the main transmission fluid, typically every 75,000 miles or five years. Neglecting this leads to premature wear of the planetary gears. Always check the service history to ensure the transfer case was explicitly included during the transmission service.
How do I identify if a diesel GLC has the older or newer engine?
Pre-facelift models from 2015 to 2019 use the 2.1-litre OM651 engine, which is reliable but noticeably unrefined and clattery. Facelift models from mid-2019 onwards feature the 2.0-litre OM654 engine. The newer unit is significantly quieter, more fuel-efficient, and fully ULEZ compliant, making it much easier to retail in urban areas.
What should I look out for when stocking the plug-in hybrid variants?
The high-voltage battery in the GLC 300e and 300de encroaches on boot space, which can deter family buyers. Check the dashboard for the maximum electric range on a full charge; early models should still display around 20 miles. Ensure both Type 2 and 3-pin charging cables are present in the boot.
Sources & further reading
Faults are compiled from documented recalls, technical bulletins, owner reports and mechanic sources, then reviewed for accuracy. This is guidance only · not a substitute for a professional inspection.
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