BMW 6 Series 635csi Engine ReplacementCompare Prices & Get Quotes

A used BMW 635csi M30 engine typically costs £1,200-£3,500 depending on mileage, condition and specification (early L-Jetronic vs later Motronic). A reconditioned unit ranges from £2,500-£5,200, while a fully rebuilt engine with warranty sits at £4,000-£7,000. Specialist fitting adds approximately £1,000-£1,600 in labour (14-20 hours at £65-£85/hr). Main dealer fitting costs 40-60% more.

• Used engine: £1,200-£3,500 supply-only
• Reconditioned: £2,500-£5,200 supply-only
• Rebuilt: £4,000-£7,000 supply-only with 12-month warranty
• Specialist fitting: £1,000-£1,600

The M30's timing chain is generally robust, but the tensioner can wear over time. The classic symptom is a rattling noise from the front of the engine on cold start that partially disappears as the engine warms up. In more advanced cases, the chain can become slack, affecting valve timing and causing power loss or rough running.

• Rattling noise on cold start is the most common early symptom
• Chain jump is rare unless the tensioner has failed completely
• Address promptly - tensioner replacement is far cheaper than a full chain job

This depends entirely on the car's condition and value. An E24 635csi typically holds £8,000-£30,000+ value depending on condition, mileage and specification. A rebuilt M30 engine at £4,000-£7,000 is typically justifiable if the car is otherwise sound and rust-free. However, if the car has significant body rot or other major issues, evaluate the total repair cost against the vehicle's value.

• £8k-£15k 635csi: reconditioned engine is viable if keeping the car long-term
• £15k+ 635csi: rebuilt engine with warranty usually makes financial sense
• Consider rust and overall condition before committing

The M30B34 was fitted from 1984-1987 and used Bosch Motronic 1.0 fuel injection, producing 218hp (non-cat) or 185hp (with catalyst). The M30B35 was fitted from 1987-1989 and used the more advanced Bosch Motronic 1.3, producing 211hp. The B35 has larger intake valves, a more breathable intake and a different cam profile.

• M30B34: Motronic 1.0, 218hp (non-cat) / 185hp (cat)
• M30B35: Motronic 1.3, 211hp (all with cat from 1987)
• B35 has improved engine management and better breathing

A typical BMW 635csi engine replacement takes 4-8 days from booking to collection, depending on parts availability and workshop workload. The M30 is an older engine, so sourcing a quality rebuilt or reconditioned unit may take 3-5 days. Supply and fit through our network typically completes within 5-8 working days.

• Supply-only: 3-5 days delivery
• Supply and fit: 5-8 days workshop time
• Specialist M30 work may add 1-2 days

Every engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty. Rebuilt and reconditioned M30 engines typically include full parts and labour cover; used engines usually carry a 3-6 month warranty depending on the supplier. Always confirm that the timing chain components are covered under the warranty terms.

• Rebuilt/reconditioned: 12 months unlimited mileage
• Used: 3-6 months (check supplier terms)
• Verify timing chain and tensioner coverage