CriticalCommonEngine

Mercedes-Benz GLC: OM651 2.1CDi Timing Chain and Guide Failure

OM651 2.1CDi Timing Chain and Guide Failure is a common engine fault on the Mercedes-Benz GLC on the 2015–2018 cars, and we rate it critical. Putting it right costs $3,500 to $8,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 17 documented faults on the Mercedes-Benz GLC.

Vehicle: Mercedes-Benz GLC
Engine: 2.1L
Years: 2015–2018
Fuel: diesel
System: Engine

This page covers the Mercedes-Benz GLC as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mercedes-Benz GLC faults17 documented faults on this model

What you are looking at

What goes wrong

GLC 220d and 250d models produced from 2015 to the 2018 model-year facelift carried the OM651 2.1-litre diesel engine, which shares the same rear-mounted timing chain design weakness found across the wider OM651 family. Nylon-composite chain guides degrade under heat and oil contamination, and the hydraulic tensioner cannot maintain adequate chain tension during cold starts when oil pressure has not yet fully built. Chain jump across camshaft sprocket teeth creates immediate risk of valve-to-piston contact and catastrophic internal damage. The OM651 was replaced by the OM654 2.0-litre diesel during the 2018 GLC facelift.

What you would notice

Cold-start metallic rattle from the rear of the engine settling after two to three minutes
Engine warning light with timing or camshaft fault codes P0016 or P0017
Hunting or unsteady idle during the first minutes of running from cold
Increased oil consumption as degraded guide material contaminates the sump

How to check it

Where to look. Rear of engine block

Cold-start the engine and listen at the firewall for a sustained rear-engine rattle before warming. Check for stored or pending codes referencing camshaft correlation using STAR diagnostics. Request full service history and confirm oil change intervals. On any example above 100,000 km without documented timing chain work, treat replacement as a near-term budget item before purchasing.

Parts involved: Timing chain.

What it costs to put right

$3,500 to $8,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the timing chain, tensioner, or guides been replaced or formally inspected?”
“Are there complete service records confirming oil changes at or below 15,000 km intervals?”
“Has the engine ever produced a rattling noise during cold starts?”

Now check the Mercedes-Benz GLC you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Mercedes-Benz GLC buyer questions

Is om651 2.1cdi timing chain and guide failure serious on a Mercedes-Benz GLC?

We rate it critical and common on the Mercedes-Benz GLC. GLC 220d and 250d models produced from 2015 to the 2018 model-year facelift carried the OM651 2.1-litre diesel engine, which shares the same rear-mounted timing chain design weakness found across the wider OM651 family. Nylon-composite chain guides degrade under heat and oil contamination, and the hydraulic tensioner cannot maintain adequate chain tension during cold starts when oil pressure has not yet fully built. Chain jump across camshaft sprocket teeth creates immediate risk of valve-to-piston contact and catastrophic internal damage. The OM651 was replaced by the OM654 2.0-litre diesel during the 2018 GLC facelift.

How much does it cost to fix on a Mercedes-Benz GLC?

$3,500 to $8,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mercedes-Benz GLC years are affected?

Our research records this fault on the 2015–2018 Mercedes-Benz GLC. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.