2012 Mercedes-Benz GL 3.0L Diesel · WP12 HFM

DVSA lists four UK campaigns against the GL covering 2012-2015 cars for brake booster function being affected by advanced corrosion in the joint area of its housing, with inspection under the Mercedes XENTRY test and booster replacement where required; the 2022/278 campaign alone covers 6,442 UK vehicles. Auto Express reported the same global action, which covered almost a million M-Class, GL-Class and R-Class cars built from 2004 and asked owners not to drive their vehicles until inspected. A corroded booster can leak air, so braking assistance drops and pedal effort rises sharply.

DVSA campaign R/2023/023 covers 51,251 UK Mercedes cars, GL models among them, because the aluminium bolts securing the steering gear could corrode and break as moisture intrudes. The remedy is replacing the aluminium bolts with steel ones, and replacing the whole steering gear if any bolt has already failed. European recall data for the same campaign (manufacturer code 4694204, KBA 012425) covers 279,443 vehicles built between April 2010 and April 2017 across ML, GL, GLE, GLS, C-Class, E-Class, S-Class and V-Class, and explains that if all three bolts break the power pack detaches from the steering gear, so power assistance fails. UK road salt is exactly the trigger.

The 3.0-litre OM642 V6 turbo-diesel powering the GL 350 CDI, GL 350 BlueTEC, and GLS 350d features an engine oil cooler nestled deep in the 'V' of the engine block beneath the turbocharger and intake runners. The original elastomeric seals harden, degrade, and rupture under sustained engine heat cycles. Oil fills the valley between cylinder banks and drains down the rear bellhousing weep hole, often misdiagnosed as an expensive rear main oil seal leak. While replacement Viton seals cost under £20, the job requires 8 to 10 hours of intensive specialist labour to strip and reassemble the top of the engine.