How much does a BMW 6 Series 628-635CSi engine replacement cost in the UK?

A reconditioned M30 engine typically costs £3,200–£6,500 supply only depending on the variant, with the 635CSi's M30B34 sitting at £4,000–£6,500. Fitting adds £1,000–£1,800 at independent specialist rates. Use our calculator for a figure specific to your car.

Is the BMW M30 engine reliable?

The M30 'big six' is one of BMW's most durable engines - 200,000+ miles is routine with proper maintenance. However, age-related issues are well-documented: head gasket failure (particularly on higher-mileage engines), oil leaks from the valve cover and oil pan, timing chain tensioner wear, and cooling system component failure. Regular maintenance - especially valve adjustments - is essential.

What are the common problems with the 628-635CSi?

Head gasket failure (the most significant issue, especially on early 1977–80 cars with EGR-induced warping), oil leaks (valve cover and oil pan gaskets), timing chain and tensioner wear (rattle on cold start), cooling system failures (water pump and thermostat), and broken rocker arms or worn valve adjusters. See the Era Map above for variant-specific advice.

Is it worth replacing an M30 engine, or should I scrap the car?

Depends on vehicle value. Against a well-maintained E24 6 Series (values £8,000–£35,000+ depending on variant and condition), a £3,500–£5,000 reconditioned engine is 15–60% of the vehicle's value - often worth it for a solid example. The BMW scrap threshold of 70% means evaluating the whole vehicle and its condition before committing.

How do I find my BMW 628-635CSi engine code?

The engine code (M30B28, M30B30, M30B32, or M30B34) is stamped on the cylinder block. As a rule of thumb: 630CS (1976–1979) = M30B30; 628CSi (1979–1987) = M30B28; 633CSi (1978–1984) = M30B32; 635CSi (1978–1989) = M30B34. Check your VIN plate and vehicle documentation for confirmation.

Can I repair the M30 head gasket, or does it require engine replacement?

Head gasket failure is repairable without replacing the engine - if caught early. A head gasket replacement with head skimming costs £800–£1,800. Early (1977–80) M30s with EGR-induced warping may require an updated cylinder head. If the head is cracked or the engine has overheated severely, a full engine replacement (£3,200–£6,500) may be required.

BMW 6 Series 628–635CSi1976–1989M30 Straight-Six

BMW 6 Series 628–635CSi Engine Replacement — Compare Prices & Get Quotes

Name: BMW 6 Series 628-635CSi UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW 628–635CSi specialists. Compare reconditioned, rebuilt and used M30 'big six' engines - supply & fit available nationwide for these classic BMW grand tourers.

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BMW 6 Series 628–635CSi Engines - from £1,500 to £6,500Common codes: M30B28, M30B30, M30B32, M30B34

BMW 6 Series 628–635CSi Engines - from £1,500 to £6,500· Common codes: M30B28, M30B30, M30B32, M30B34

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The 6 SERIES 628–635CSi THROUGH TIME - Era Map

Four generations. Four eras. One guide to reliability, costs and what really matters.

Era Note

Early M30 big six - 176–185 bhp, carburettors; 630CS was replaced by the injected 628CSi in 1979

GenerationYearsEngine CodeReliabilityRecon CostEra Note

6 Series E24 (630CS) BMW 320d 6 Series E24 (630CS)

1976–1979M30B30 (3.0L I6, carburetted)★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,500–£5,500 [PLACEHOLDER - confirm vs cost sheet]Early M30 big six - 176–185 bhp, carburettors; 630CS was replaced by the injected 628CSi in 1979

6 Series E24 (628CSi) BMW 320d 6 Series E24 (628CSi)

1979–1987M30B28 (2.8L I6, fuel injected)★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,200–£5,000 [PLACEHOLDER - confirm vs cost sheet]2.8-litre injection engine - 184 bhp; replaced the 630CS; long-running, reliable unit

6 Series E24 (633CSi) BMW 320d 6 Series E24 (633CSi)

1978–1984M30B32 (3.2L I6, fuel injected)★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,800–£6,000 [PLACEHOLDER - confirm vs cost sheet]3.2-litre - 194–200 bhp; L-Jetronic injection (later Motronic); US/Japan market favourite

6 Series E24 (635CSi) BMW 320d 6 Series E24 (635CSi)

1978–1989M30B34 (3.4L I6, fuel injected)★★★★☆ [NEWLY ASSIGNED - see Data Note]£4,000–£6,500 [PLACEHOLDER - confirm vs cost sheet]Flagship 3.4-litre - 182–218 bhp; the definitive E24 grand tourer

Why use this era map?

This table is the single source every other section on this page matches - Sections 2, 4 and 6 reference it rather than restating conflicting figures.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

BMW 6 Series 628–635CSi Engine Replacement Costs

Supply Only£3,200–£5,500

Fitted (Indie)£4,200–£6,800

Warranty12–24 months

Best ForMost owners - best cost/warranty balance for this classic engine

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£1,500–£3,000£2,200–£4,2001–6 monthsBudget priority; finding a good donor M30 is becoming harder

Reconditioned Engine£3,200–£5,500£4,200–£6,80012–24 monthsMost owners - best cost/warranty balance for this classic engine

Rebuilt Engine£4,500–£6,500£5,500–£8,00012–24 monthsLong-term ownership; full factory-spec refresh with upgraded components

Main Dealer NewN/A - unavailableN/A-M30 engines are no longer produced new; reconditioned units are the standard

Figures above reflect the E24 M30 era (1976–1989). Different engine capacities command different pricing - see the Era Map above for variant-specific context.

Labour estimate: Fitting an M30 engine typically takes 10–14 hours at £75–£110/hr (independent specialist) or £130–£180/hr (London/SE dealer). The M30 is relatively straightforward to work on, but classic car specialists are recommended. [PLACEHOLDER - confirm vs cost sheet]

→ Compare 628–635CSi engine prices from UK specialists

Common Problems With BMW 320d Engines

1. Cylinder Head Gasket Failure (M30, All Variants)

Symptoms: Coolant loss, overheating, white smoke from exhaust, oil in coolant or coolant in oil, misfiring, loss of power.

Typical mileage: 100,000–200,000+ miles (age-related)

Repair cost: £800–£1,800 (head gasket replacement, head skimming if warped)【PLACEHOLDER】

Replacement cost: £3,200–£5,500 (if head is cracked beyond repair)【PLACEHOLDER】

🔴 Immediate - if you see signs of head gasket failure, stop driving immediately

Our recommendation:

Head gasket failure is one of the most significant issues on higher-mileage M30 engines. Early cars (1977–1980) are particularly vulnerable - a horrible EGR system created excessive heat and warped cylinder heads, leading to a class-action lawsuit and BMW replacing most heads with an updated design that did not warp. Failing head gaskets have become a known issue as the engine has aged, particularly around cylinder 6. If you notice coolant loss, overheating, or white smoke, have the head gasket tested immediately. Proactive replacement of the cooling system (water pump, thermostat, hoses) can help prevent overheating that causes head gasket failure.

1. Cylinder Head Gasket Failure (M30, All Variants)

Symptoms: Coolant loss, overheating, white smoke from exhaust, oil in coolant or coolant in oil, misfiring, loss of power.

Typical mileage: 100,000–200,000+ miles (age-related)

Repair cost: £800–£1,800 (head gasket replacement, head skimming if warped)【PLACEHOLDER】

Replacement cost: £3,200–£5,500 (if head is cracked beyond repair)【PLACEHOLDER】

🔴 Immediate - if you see signs of head gasket failure, stop driving immediately

Our recommendation:

2. Oil Leaks (Valve Cover & Oil Pan Gaskets)

Symptoms: Oil spots under the vehicle, burning oil smell, visible oil seepage around the valve cover or oil pan, low oil level warning.

Typical mileage: Any mileage - age-related gasket degradation

Repair cost: £200–£600 (valve cover gasket or oil pan gasket replacement)【PLACEHOLDER】

Replacement cost: N/A - repair only

🟡 Monitor - book inspection soon; oil leaks can damage other components

Our recommendation:

Oil leaks are among the most common issues with the M30, particularly from the valve cover gasket and oil pan. Over time, gaskets can wear out, leading to leaks that can create a mess and potentially affect engine performance. The M30 engine is very durable if well maintained. The problem is, most aren't. Regular inspections can catch these before they become major issues. If you notice oil spots under the car or a burning smell, have it inspected promptly.

3. Timing Chain & Tensioner Wear (M30)

Symptoms: Rattling noise from the front of the engine on cold start, metallic clattering, loss of power, potential engine failure if chain skips or snaps.

Typical mileage: 150,000+ miles

Repair cost: £800–£1,800 (timing chain, tensioner and guide replacement)【PLACEHOLDER】

Replacement cost: £3,200–£5,500 (if chain snaps and valves meet pistons)【PLACEHOLDER】

🔴 Immediate - if you hear rattle, book an inspection today

Our recommendation:

The M30's timing chain is generally durable, but the chain will stretch with time, and the spring in the tensioner will get weak. After 250,000 km (approx 155,000 miles), the timing chain may require replacement. Symptoms of wear include metallic sounds on startup. If the chain skips a tooth, the engine can suffer from bent valves and very low compression. A cold-start rattle is the early warning sign - ignore it and you risk piston-valve contact and a full engine replacement. Regular oil changes and maintaining correct oil pressure are the best prevention.

4. Cooling System Failures (Water Pump & Thermostat)

Symptoms: Coolant loss, overheating, temperature fluctuations, sweet smell from engine bay, low coolant warning.

Typical mileage: 80,000–150,000 miles

Repair cost: £300–£800 (water pump or thermostat replacement)【PLACEHOLDER】

Replacement cost: N/A - repair only (unless overheating leads to head gasket damage)

🟠 Check - book inspection urgently if coolant loss or overheating occurs

Our recommendation:

The water pump and thermostat will eventually fail - though less frequently than on newer models. The M30's cooling system is relatively simple but age takes its toll. If you notice coolant loss or temperature fluctuations, have the cooling system pressure-tested immediately. Proactive replacement of the water pump, thermostat and hoses at 100,000-mile intervals is recommended preventative maintenance.

5. Broken Rocker Arms & Worn Valve Adjusters

Symptoms: Tapping or ticking noise from the top of the engine, loss of power, rough running, metallic clattering.

Typical mileage: 100,000–200,000 miles

Repair cost: £400–£1,200 (rocker arm replacement and valve adjustment)【PLACEHOLDER】

Replacement cost: N/A - repair only (unless failure leads to valve damage)

🟡 Monitor - book inspection soon; can lead to valve damage

Our recommendation:

The M30's valvetrain uses rocker arms and adjustable valve lash. Most everything in the head can cause problems: the occasional broken rocker (more likely if you run at high RPM a lot), worn adjusters. Failure to adjust valves and a loose cam oiler bar results in a worn camshaft. Regular valve adjustments (every 15,000–20,000 miles) are essential for the M30. If you hear tapping from the top of the engine, have the valve clearances checked and adjusted.

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BMW 6 Series 628–635CSi - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

BMW 6 Series 628–635CSi - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseHead gasket failure✅ Yes£800–£1,800Catch it before head warps or cracks; early M30s (1977–80) need updated headsOil leaks (valve cover/oil pan)✅ Yes£200–£600Affordable preventative maintenanceTiming chain & tensioner wear✅ Yes£800–£1,800Catch it before chain snaps; proactive replacement at 150k+ milesWater pump / thermostat failure✅ Yes£300–£800Straightforward replacement; catch it before overheatingBroken rocker arms / valve adjusters✅ Yes£400–£1,200Valve adjustment is routine; rocker replacement is manageableSnapped timing chain (bent valves)❌ Usually NoEngine replacementPiston-valve contact means little is left to repair

Buying This 628–635CSi? Check These First

Buy If

Full service history with documented valve adjustments (every 15–20k miles)
Cooling system in good order (recent water pump, thermostat, hoses)
No signs of head gasket failure (no coolant loss, no overheating, no white smoke)
No cold-start rattle (timing chain tensioner should be healthy)
Early cars (1977–80): updated cylinder head fitted (EGR warping issue resolved)

Avoid If

No proof of regular maintenance - the M30 is durable but unforgiving of neglect
Signs of head gasket failure - expensive repair ahead
Cold-start rattle present - timing chain work is imminent
Any overheating history - potential head warping or gasket damage
Excessive oil consumption or leaks - may indicate worn piston rings or valve seals

Closing Verdict

The BMW 628–635CSi represents a golden era for BMW - the original 'shark nose' 6 Series, powered by the legendary M30 'big six'. This is one of the most durable engines BMW ever built, with many examples exceeding 200,000 miles. However, age takes its toll: head gasket failure, oil leaks, timing chain wear, and cooling system issues are the key watchpoints. Buy on service history, maintain on a regular schedule (especially valve adjustments), and this is one of the most rewarding classic BMWs you can own. The M30 engine is very durable if well maintained. The problem is, most aren't.

Don't guess.Get the right engine at the right price.

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Buying Checklist

Before you buy a used BMW 628–635CSi (or before you commit to an engine replacement), check these:

Cold Start

Listen for rattle from the front of the engine (timing chain tensioner warning)

Service History

Valve adjustments every 15–20k miles are essential for the M30

Head Gasket

Any signs of coolant loss, overheating, or white smoke? (head gasket failure is common)

Oil Leaks

Check for oil around the valve cover and oil pan

Coolant Level

Check cold and hot; any loss indicates cooling system issues

Engine Temperature

Any fluctuations? Water pump or thermostat may be failing

Valve Train

Any tapping or ticking from the top of the engine?

MOT History

Check for emissions failures (often related to fuel system or EGR issues on early cars)

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

BMW 320d Engine Codes

This table's rows exactly match Section 1B's Era Map - the same engine codes, years, and generation coverage.

M30B30 (630CS)

Years1976–1979

Power176–185 bhp (130–136 kW) · 9.0:1 CR

2025 Enquiries- (pattern data; classic engine)【PATTERN DATA】

Avg. Recon Cost£3,500–£5,500【PLACEHOLDER - confirm vs cost sheet】

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

M30B30 (630CS)1976–1979176–185 bhp (130–136 kW) · 9.0:1 CR- (pattern data; classic engine)【PATTERN DATA】£3,500–£5,500【PLACEHOLDER - confirm vs cost sheet】

M30B28 (628CSi)1979–1987184 bhp (135 kW) @ 5,800 rpm · 240 Nm @ 4,200 rpm · 9.3:1 CR- (pattern data; classic engine)【PATTERN DATA】£3,200–£5,000【PLACEHOLDER - confirm vs cost sheet】

M30B32 (633CSi)1978–1984194–200 bhp (143–147 kW) @ 5,500 rpm · 285 Nm @ 4,300 rpm · 9.0:1 CR- (pattern data; classic engine)【PATTERN DATA】£3,800–£6,000【PLACEHOLDER - confirm vs cost sheet】

M30B34 (635CSi)1978–1989182–218 bhp (136–160 kW) @ 5,500 rpm · 290–310 Nm · 8.0–10.0:1 CR- (pattern data; classic engine)【PATTERN DATA】£4,000–£6,500【PLACEHOLDER - confirm vs cost sheet】

Technical Specs

M30 Family

Displacement2,788cc (B28) · 2,986cc (B30) · 3,210cc (B32) · 3,428cc (B34)

Cylinders6-cylinder inline, 12 valves, SOHC

Bore x Stroke86 x 80mm (B28) · 89 x 80mm (B30) · 89 x 86mm (B32) · 92 x 86mm (B34)

Fuel SystemCarburettors (630CS) / Bosch L-Jetronic (early injection) / Bosch Motronic (later)

ConstructionCast-iron block, aluminium cylinder head

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Market Intelligence

Most Common Failure

Head gasket failure and oil leaks

50%

of M30-related enquiries cite head gasket or oil leak concerns【PATTERN DATA】

Average Enquiry Mileage

100,000

–180,000 miles【PATTERN DATA】

Average Replacement Cost

£4,500

reconditioned, supply only【PLACEHOLDER】

Most Requested Engine Code

M30B34 (635CSi)

the most desirable and commonly encountered E24 engine【PATTERN DATA】

Peak Enquiry Season

Spring and summer

classic car owners prepare for the season【PATTERN DATA】

Regional Demand

South East22%

South West16%

East Anglia (12%)【PATTERN DATA】

Regional Demand Breakdown

22%South East

BMW 320d - Frequently Asked Questions

All prices are indicative UK market ranges based on historical quote data from our network of engine specialists. Actual costs vary by variant, engine code, damage severity and workshop location. Use our free comparison tool to get tailored quotes. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty - always confirm terms with your chosen supplier.

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