The manufacturer issued a recall for it, covering more than 100,000 cars built between February and November 2014. The repair is free under the campaign. The visible signs are oil traces at the back of the engine and a burnt smell.

The characteristic course of events: the panoramic roof glass shatters while driving, with no impact, with a loud bang. Across the whole group 108 complaints use the wording "exploded / shattered into pieces", 155 say it happened while driving, 38 specifically note that nothing struck the roof, and 43 complaints mention injury or cuts from the glass.

By measurement the affected group is primarily the W205 C-Class (2015 to 2017), plus the MFA platform GLA (X156) and CLA (C117) in the 2014 to 2015 model years.

There is no rattle beforehand and no warning. The traces of a replacement show on the seal and the bonding. The replacement is not cheap, and the broken glass falls into the cabin.

The complaint database is American, and the panoramic roof is more common there as an option. The phenomenon itself does not depend on the market.

1) Delphi piezo injectors. According to the German technical press the fault affected the two more powerful versions (125 kW / 170 hp and 150 kW / 204 hp). The weaker versions got solenoid injectors and were not affected. The fault could show up as early as around 50,000 km: the engine drops into limp mode, power is limited, and the car can still be driven slowly. Because of supply shortages the maker at first replaced only the failed injector rather than all four, so some owners went back four times. Later they moved to replacing the full set. From spring 2011 every 220 CDI version got solenoid injectors; the 250 CDI kept piezo injectors throughout, in several revised versions.

2) Timing chain. The engine runs on gears plus a short simplex roller chain. Increased chain wear (typically caused by a faulty chain tensioner) shows up occasionally at higher mileage. The replacement is very labour intensive, because the chain sits on the rear of the engine, on the gearbox side. The labour is the bigger part of the bill.

In November 2014 the chain tensioner caused trouble again: it can release, and engine oil can leak. The maker recalled cars built between February and November 2014. If the car falls in that window, check that the campaign was carried out.

The water pump can leak too.

Driven with a faulty mechatronics unit, the wet dual clutch wears faster. The mechanical part (synchros, differential bearing) tends to appear at high mileage.

This is not the longitudinal 7G-Tronic (722.9): a different casing and a different fault pattern.

For Germany the suspicion was confirmed in KBA recalls supervised by the authority:

• KBA 8227: GLC 220d / GLC 250d, 06.2015 to 06.2018
• KBA 8251, 8252, 8253, 8314: Vito 2.2 diesel, 09.2014 to 09.2016 (partly classed as M1 passenger cars, partly as N1 commercial vehicles)

The ADAC lists these on top: C 220d / C 250d and C 220 / C 250 BlueTEC (12.2013 to 05.2018), S 300 BlueTEC HYBRID / S 300 h (12.2013 to 09.2016), ML 250 BlueTEC (08.2011 to 06.2015), and possibly the GLE 250d. In October 2019 the KBA ordered a third recall as well.

A large share of the cars exported out of the German market come from exactly this group, and the paperwork does not show whether the software update was done. In most countries this alone does not take the car off the road, but it hurts the car's value and how easily you can sell it on.

After the update many owners report higher fuel consumption and worse drivability: you notice that while driving, not from the documents. And in March 2021 the Stuttgart regional court found deliberate, immoral conduct on the maker's part and awarded a C 220 buyer around 25,000 euro in damages (7 O 224/20).