Mercedes Benz GLC Class 350d/400d Engine ReplacementCompare Prices & Get Quotes

Short summary: A rebuilt GLC 350d OM642 engine costs £3,500-£5,500 supply-only; a rebuilt GLC 400d OM656 engine costs £4,500-£7,500 supply-only. Fitting adds £800-£1,500 depending on complexity - the OM656's inline-six is slightly more accessible than the OM642's V6.

• GLC 350d (OM642.873): rebuilt unit £3,500-£5,500; used engine from £1,800
• GLC 400d (OM656.929): rebuilt unit £4,500-£7,500; used engine from £2,200
• V6 oil cooler seal replacement (labour only): £1,000-£1,500 at specialist
• Price depends on engine code, year, mileage, and supplier warranty length

Short summary: The OM642 V6 is fundamentally robust but has one dominant weak point - oil cooler seals that leak into the engine V. Catch it early and the engine will exceed 200,000 miles. Ignore it and oil starvation destroys the bottom end.

• Oil cooler seals fail between 70k-110k miles - a £5 part with £900 labour
• Burning oil smell from the engine bay is the classic warning sign
• Oil dripping onto the undertray from the rear of the engine
• If caught early, seal replacement alone is the value play
• Full rebuilt engine with upgraded Viton seals resolves the design flaw permanently

Short summary: The OM656 straight-six is a modern, powerful diesel with excellent performance - 330hp and 700Nm. However, a global recall for coolant pump vacuum leaks affected approximately 800,000 OM654/OM656 vehicles. Ensure your GLC 400d has had the recall performed.

• Coolant pump vacuum leak can allow coolant into the vacuum system
• Risk of increased temperature and potential fire
• Recall involves replacing coolant pump switch valve and updating software
• Post-recall water pump instability reported on some vehicles
• Otherwise robust - the OM656 is considered well-engineered

Short summary: Properly maintained OM642 V6 diesels routinely reach 200,000-250,000 miles before major work. The OM656 straight-six is too new for definitive long-term data, but early indications suggest similar longevity with proper maintenance.

• OM642 (350d): 200,000+ miles with regular servicing and early oil cooler seal attention
• OM656 (400d): too early for definitive data - first major repairs expected after 100k-150k miles
• Service interval is 10,000 miles or 12 months - use Mercedes-spec low-SAPS oil (MB 229.52)
• Late oil changes are the #1 cause of preventable failure on both engines

Short summary: Yes, if the GLC is otherwise in good condition with no rust or major electrical faults. A rebuilt OM642 costs £3,500-£5,500 - far less than replacing a £15,000-£40,000 vehicle. The GLC 400d's higher value (£25,000-£40,000) makes replacement even more financially justifiable.

• GLC 350d values: £15,000-£25,000 depending on mileage and condition
• GLC 400d values: £25,000-£40,000 - premium SUV residual values remain strong
• Rebuilt engine with upgraded components fixes original weak points
• Supply & fit typically £4,500-£9,000 depending on engine code
• New engine includes 12-month unlimited mileage warranty

Short summary: Mercedes-Benz specifies low-SAPS oil meeting MB 229.51 or 229.52 - typically 5W-30. The OM642 V6 requires approximately 8.5 litres; the OM656 straight-six requires approximately 8 litres.

• OM642 (350d): MB 229.52 5W-30 low-SAPS - protects DPF and emissions systems
• OM656 (400d): MB 229.52 5W-30 low-SAPS - 8L capacity
• Never use non-approved oil - destroys timing chain tensioners and hydraulic lifters
• Change every 10,000 miles or 12 months - stretched intervals cause turbo and bearing failure