How much does a BMW 324d or 324td engine replacement cost in the UK?

A reconditioned M21 engine typically costs £800–£2,500 supply only depending on which variant (naturally aspirated or turbocharged), with used units available from £500–£1,200. Fitting adds £700–£1,500. Use our calculator for a figure specific to your car. These engines are increasingly rare.

Is the BMW 324d / 324td engine reliable?

The naturally aspirated M21 in the 324d has a reputation for sturdiness and reliability. The turbocharged M21 in the 324td is less reliable - it suffers from cylinder head cracking and early electronic injection pump issues. Both engines require regular timing belt changes at 40,000-mile intervals - a snapped belt is catastrophic.

What are the common problems with the BMW 324d and 324td?

324d: timing belt failure (requires regular replacement). 324td: cylinder head cracking (the defining issue), timing belt failure, and early electronic injection pump failure (DDE system). The 324td's cylinder head is the single biggest concern.

Is it worth replacing a BMW 324d / 324td engine, or should I scrap the car?

These cars are rare and increasingly valuable - the 324td had the lowest production figures of any factory E30, with only around 27,000 units made. A well-kept example is worth £5,000–£15,000+ depending on condition. A £1,500–£2,500 recon is only 15–30% of the car's value - well within the 70% BMW threshold. Replacement is almost always worthwhile on a cherished example.

How do I find my BMW 324d / 324td engine code?

The engine code is M21D24 - both variants share the same core engine. The naturally aspirated version is fitted to the 324d (1985–1990); the turbocharged version is fitted to the 324td (1987–1993). The 324td was never officially sold in the UK, so most UK cars are private imports.

Can I repair the M21 timing belt, or does it need replacement?

The timing belt must be replaced - it's a wear item. Replacement interval is 40,000 miles or 6 years. If the belt snaps, the engine is typically destroyed. A preventative belt replacement (£300–£600) is far cheaper than a full engine replacement (£800–£2,500+). At the first sign of ticking from the front of the engine, book an inspection immediately.

BMW 3 Series 324d / 324td1985–19932.4-litre M21 Diesel

BMW 324d / 324td Engine Replacement — Compare Prices & Get Quotes

The 324d and 324td are rare E30 diesels powered by BMW's first diesel engine - the M21. The naturally aspirated 324d is slow but frugal; the turbocharged 324td is quicker but suffers from cylinder head and injection pump issues. Get quotes from UK specialists for reconditioned, rebuilt and used units today.

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BMW 324d / 324td Engines - from £500 to £3,000Common codes: M21D24, M21D24 Turbo

BMW 324d / 324td Engines - from £500 to £3,000· Common codes: M21D24, M21D24 Turbo

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The 324d / 324td THROUGH TIME - Era Map

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

GenerationYearsEngine CodeReliabilityRecon CostEra Note

Why use this era map?

Every cost guide, reliability rating and engine code on this page is aligned to the data above. This keeps everything consistent and trustworthy.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

BMW 324d / 324td Engine Replacement Costs

Supply Only£800–£1,800

Fitted (Indie)£1,800–£3,000

Warranty12–24 months

Best ForMost owners - best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£500–£1,200£1,200–£2,2001–6 monthsBudget priority; M21 engines are scarce

Reconditioned Engine£800–£1,800£1,800–£3,00012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£1,500–£3,000£2,500–£4,50012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer NewN/A - no longer availableN/A-N/A - specialist rebuild only

Figures above reflect the current market for the rare E30 324d/324td. The naturally aspirated M21 typically sits at the lower end; the turbocharged M21 commands a premium. These engines are increasingly scarce - reconditioned units are hard to find.

Labour estimate: Fitting an M21 engine typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer).

→ Compare 324d / 324td engine prices from UK specialists

Common Problems With BMW 320d Engines

1. Timing Belt Failure (Both Engines)

Symptoms: Engine stops suddenly, ticking from the front of the engine, complete loss of power, catastrophic engine failure

Typical mileage: 40,000–60,000 miles (belt interval)

Repair cost: £300–£600 (preventative timing belt replacement)

Replacement cost: £800–£2,500 (if belt snaps - piston-valve contact)

🔴 Immediate - if the belt fails, the engine stops instantly and internal damage is highly likely

Our recommendation:

Like the M20 petrol engine it's based on, the M21 uses a timing belt - not a chain. BMW recommends replacement every 40,000 miles or 6 years. A snapped timing belt on this interference engine means valve and piston damage - effectively an engine replacement. If you're buying an M21-engined E30, demand proof of timing belt replacement. Budget for it immediately if there's no evidence. These engines are becoming rare - a snapped belt can write off the car.

Read the full timing belt failure guide

1. Timing Belt Failure (Both Engines)

Symptoms: Engine stops suddenly, ticking from the front of the engine, complete loss of power, catastrophic engine failure

Typical mileage: 40,000–60,000 miles (belt interval)

Repair cost: £300–£600 (preventative timing belt replacement)

Replacement cost: £800–£2,500 (if belt snaps - piston-valve contact)

🔴 Immediate - if the belt fails, the engine stops instantly and internal damage is highly likely

Our recommendation:

Read the full timing belt failure guide

2. Cylinder Head Cracks (324td Turbo)

Symptoms: Coolant loss with no visible external leak, white smoke from exhaust, overheating, pressurised cooling system, misfire on cold start, oil in coolant

Typical mileage: 80,000–150,000 miles

Repair cost: £800–£1,800 (cylinder head replacement or welding)

Replacement cost: £1,200–£2,500 (if overheating causes bottom-end damage)

🔴 Immediate - any overheating or coolant loss on a 324td requires immediate investigation

Our recommendation:

The 324td's M21 turbo engine is notorious for cylinder head cracking. The turbocharged engine runs hotter than the naturally aspirated version, and the cylinder head is a known weak point. German sources describe the issue as "Kopfrisse, Kopfrisse, Kopfrisse" - head cracks, head cracks, head cracks. If you're buying a 324td, have the cylinder head inspected by a specialist. A cracked head can be welded or replaced, but it's an expensive job. Regular cooling system maintenance and avoiding overheating are essential.

Read the full cylinder head failure guide

3. Injection Pump Failure (324td)

Symptoms: Hard starting, rough idle, loss of power, black smoke, engine warning light, engine won't start

Typical mileage: 100,000–200,000 miles

Repair cost: £500–£1,200 (injection pump rebuild or replacement)

Replacement cost: N/A - repair only

🟡 Monitor - book inspection soon

Our recommendation:

The 324td uses one of the first digital diesel injection pumps (DDE - Digital Diesel Electronics) in a passenger car. This early electronic injection pump is a known weak point - if it fails, the car simply won't run. Some owners convert to a mechanical pump from the earlier 524td to avoid the electronic pump's complexity. If you experience hard starting or rough running on a 324td, have the injection pump diagnosed by a specialist. Rebuilding or replacing the pump is expensive but far cheaper than scrapping a rare car.

Read the full injection pump failure guide

Weighing Your Options?

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324d / 324td - 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.

324d / 324td - 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 SenseTiming belt (preventative, both)✅ Yes£300–£600Standard maintenance - the most important investment in any M21Timing belt failure (engine damage)❌ Usually NoEngine replacementIf belt snaps, valves hit pistons - replacement is the only optionCylinder head crack (324td)✅ Yes£800–£1,800Welding or replacement - expensive but viable on a rare carOverheating damage (324td)⚠️ Sometimes£1,200–£2,500Viable on a cherished example; borderline if other issues existInjection pump failure (324td)✅ Yes£500–£1,200Specialist rebuild or replacement - far cheaper than scrapping the carFuel system issues (both)✅ Yes£200–£800Well-understood by diesel specialists - catch before pump damage

Buying This 324d / 324td? Check These First

Buy If

Documented timing belt replacement within the last 40,000 miles or 6 years - the single most important check on the M21
324td with proof of cylinder head work - evidence of the head being checked, welded or replaced
Full service history with regular oil changes - the M21 is robust but ageing
A well-maintained example - these cars are rare and increasingly valuable

Avoid If

No proof of timing belt replacement - budget for it immediately or walk away
324td with any signs of coolant loss or overheating - cylinder head cracks are likely
324td with hard starting or rough running - injection pump issues are expensive
Poor service history or evidence of neglect - these engines are unforgiving

Closing Verdict

The M21 is BMW's first diesel engine - a robust, simple straight-six based on the M20. The naturally aspirated 324d is slow but reliable, capable of 40+ mpg and extremely high mileages with basic maintenance. The turbocharged 324td is quicker but has known weaknesses: cylinder head cracks and early electronic injection pump issues. Both engines are rare in the UK - they were never officially sold here. If you find one, buy on history, not on price. A well-maintained 324d is a dependable classic; a neglected 324td is a money pit.

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

→ Compare 324d / 324td engine prices before you buy

Don't Guess. Compare.

Get real quotes from vetted UK specialists and make the right call for your 320d.

→ Compare 324d / 324td engine prices before you buy

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Buying Checklist

Before you buy a used BMW 324d or 324td (or before you commit to an engine replacement), check these:

1. Timing Belt History

Has it been changed within the last 40,000 miles or 6 years? This is the single most critical check on the M21

2. Coolant Condition

Any signs of oil in the coolant or coolant loss? (cylinder head crack warning on 324td)

3. Cold Start

Does it start cleanly from cold? Any excessive smoke or hard starting? (injection pump or glow plug warning)

4. Overheating History

Any evidence of overheating in the service history? (324td cylinder head warning)

5. Oil Condition

Any signs of coolant contamination in the oil? (milky appearance - head gasket or crack)

6. Smoke

Black smoke under acceleration? (injection pump or turbo issues on 324td)

7. Engine Warning Light

Have codes been read? (DDE system on 324td - specialist required)

8. MOT History

Check for emissions-related failures (injection pump or EGR issues on 324td)

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 match Section 1B's Era Map exactly - two engine variants across the 324d/324td's production run.

M21D24 (naturally aspirated)

Years1985–1990

Power84 hp

2025 Enquiries[PATTERN DATA]

Avg. Recon Cost£800–£1,500 [BMW-QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

M21D24 (naturally aspirated)1985–199084 hp[PATTERN DATA]£800–£1,500 [BMW-QUOTE]

M21D24 Turbo1987–1993115 hp[PATTERN DATA]£1,200–£2,500 [BMW-QUOTE]

Technical Specs

M21D24 - both variants

Displacement2,443cc (2.4-litre)

CylindersStraight-6

Compression Ratio22.0:1

Fuel SystemSwirl chamber injection, distributor injection pump

TurbochargerGarrett T03 (324td only)

ValvetrainSOHC, 2 valves per cylinder, timing belt

→ Compare 324d / 324td engine prices for your BMW

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Market Intelligence

Most Common Failure

324d: Timing belt failure / 324td: Cylinder head cracking

the defining risk of each variant

Average Enquiry Mileage

100,000

–180,000 miles【PATTERN DATA】

Average Replacement Cost

£800

–£2,500 reconditioned, supply only depending on variant【BMW-QUOTE】

Most Requested Engine Code

M21D24 Turbo

the rare 324td【PATTERN DATA】

Peak Enquiry Season

Spring

classic car season【PATTERN DATA】

Regional Demand

South East18%

South West14%

Midlands (12%)【PATTERN DATA】

Regional Demand Breakdown

18%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.

Trusted M21 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real 324d and 324td owners, as part of the Engine Finders network, across both naturally aspirated and turbocharged variants - no matter which rare E30 diesel you own.
Compare 324d / 324td Engine Replacement Companies
see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who genuinely understand the M21's timing belt, cylinder head, and injection pump nuances.
UK Engine Replacement Services for 324d / 324td
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Find the best BMW 324d or 324td engine replacement UK owners trust. Compare prices from trusted specialists on EnginesMarket today and keep this rare E30 diesel on the road.

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12-Month Warranty

As standard

Nationwide Delivery

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