BMW 320i (E30) engine: which one, problems and replacement

The BMW 320i in the second 3 Series generation (E30, built 1982–1994) was built with one engine, the M20B20: a 2.0 L petrol inline-6 with 129 hp.

Below you will find how to identify the engine in your 320i, the faults to look for, current prices for a replacement and the swap options that make sense.

• Generation: second 3 Series, 1982–1994
• Body styles: E30 (saloon, Touring, coupé, convertible)
• Engines: M20B20
• Output: 129 hp
• Replacement engines in stock: ask the desk for the next arrival

Which engine is in your 320i?

M20B20 in the 320i

The M20B20 was used in the E30 320i, built 1977–1992. It is a 2.0 L naturally aspirated petrol inline-6 with 129 hp and 164 Nm.

Reading the code: M marks an M-series code, the naming BMW used for its engine families up to the early 2000s; 20 is the family number; B stands for petrol (from the German Benzin); 20 is the capacity in decilitres, so 2.0 litres.

320i engines by model year

The 320i kept the same engine for the whole E30 run, which makes ordering simple: any unit with the same code fits, subject to the gearbox, drive type and sump.

Other cars with the same engine as the 320i

A replacement engine does not have to come from another 320i. These models left the factory with the same engine code, so a unit from any of them is a candidate donor once the sump, mounts and ancillaries are matched to your car.

M20B20: BMW E28 520i, BMW E34 520i.

How to confirm your engine code

The 320i only used the M20B20, but the exact version can still change with the build date, gearbox and market. Send us the last seven characters of the VIN and we read the engine code from BMW's records, or look for the code stamped on the block. How to find your BMW engine code.

Known 320i engine problems

The M20B20 in the 320i shares the known weak points of the M20 family. Full M20 guide.

Timing belt failure. The M20 is an interference engine. If the belt or tensioner fails, pistons hit valves and the head is scrap. Belts should be changed every 60,000 km or four years, whichever comes first.

Cylinder head cracks. Heads crack between the camshaft journals or between valve seats after overheating. Coolant loss and a sweet smell are the clues.

Rocker arm and shaft wear. Rocker arms can crack and the retaining clips can walk off the shaft. The 'rocker arm fix' with improved clips is a known upgrade.

Oil spray bar and cam wear. A loose or blocked spray bar starves the cam lobes. The result is a worn cam and noisy valve train.

Water pump and thermostat. The water pump is driven by the timing belt and is normally changed with it. A weeping pump can soak the new belt.

Symptoms to watch for on the 320i

Engine stops suddenly and will not restart. On belt-driven engines, a snapped timing belt. Do not keep cranking: on an interference engine the valves are probably already bent.

Looking after the 320i engine

• Oil: 10W-40 or 15W-40 semi-synthetic, about 4.25 litres with filter.
• Service interval: Oil every 7,500 km; valve clearances every 15,000 km; belt on time, not only on distance.
• Timing drive: Rubber timing belt with tensioner, changed with the water pump every 60,000 km or four years.
• Workshop notes: Valve clearance is set cold at about 0.25 mm with eccentric adjusters. Use a new head bolt set whenever the head comes off.

Buying a used engine for the 320i: checklist

1. Look at the oil and coolant. Clean oil without metal particles and coolant without oil are good signs. Milky oil, oily coolant or a burnt smell mean the engine needs further checks before it is fitted.
2. Compression or leak-down figures. Even compression across all cylinders tells you more than mileage. Ask for the figures, not just a pass or fail, and compare the highest and lowest readings: a spread above 10 to 15 percent deserves a question.
3. Why your old engine failed. Before fitting a replacement, find out why the original failed. An overheating radiator, a blocked intercooler or a failed turbo can destroy a second engine if they are not fixed.
4. Gearbox and flywheel match. Manual and automatic engines differ at the flywheel or flexplate, and sometimes at the crankshaft spigot. Make sure the engine you buy matches your gearbox or that you transfer the right parts.
5. Photographs from every side. Good suppliers photograph the actual engine you will receive. Look for the block stamp, the sump, the timing cover and any broken brackets or connectors in the pictures.
6. Timing belt history. A timing belt must be changed on time and distance. With no dated record, treat the belt, tensioner and water pump as due and replace them before the first start.
7. Originality and numbers. For collectible cars, the engine number and correct ancillaries add value. Photograph the stamp and keep it with the car's documents.

BMW 320i replacement engine cost

We do not have a 320i engine on the shelf at the moment. Send us your VIN or the code you need and the desk will tell you when the next unit arrives and what it will cost.

On top of the engine, budget for the workshop's labour and the parts that are best replaced while the engine is out: engine mounts, the rear main seal, cooling parts, a clutch or converter seal, fluids and filters.

Will it fit my 320i?

Engine swaps and upgrades for the 320i

These engines were fitted to other versions of the E30 at the factory, which makes them the most practical upgrades: the body was designed around them and many parts are shared.

Can I fit the M20B23 in my 320i?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M20B23 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 10 hp and 41 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the M42B18 in my 320i?

It is a conversion rather than a replacement: the M42B18 is an inline-4 and your M20B20 an inline-6, so mounts, sump, cooling, exhaust, wiring and the engine control unit all change. The gain is 11 hp and 11 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the M20B25 in my 320i?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M20B25 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 41 hp and 62 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Fitting a replacement engine in the 320i

1. Fit a new timing belt kit. Fit a new belt, tensioner and water pump and set the timing with the correct tools before the first start.
2. Fill with the right oil and prime it. Fill with new oil of the correct specification and a new filter. Crank with the fuel and ignition disabled until oil pressure builds.
3. Coding and adaptations. On modern BMWs, the engine ECU must be matched to the car's immobiliser (CAS, FEM or BDC). Reset adaptations, register the battery and clear faults with diagnostic software.
4. First start and leak check. Start the engine, let it idle and watch oil pressure, temperature and fault codes. Check for leaks and bleed the cooling system.
5. First 1,000 km. Drive gently for the first few hundred kilometres, vary the engine speed and avoid full load. Change the oil and filter after about 1,000 km to remove any assembly debris.

The full fitting and first-start procedure.

320i engine questions

How much is a replacement M20B20 engine for a BMW E21 320i?

A used M20B20 for the BMW E21 320i costs from about 1.000 € to 1.700 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.

A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B20 you buy is photographed and checked in Hamburg before it is listed.

Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all M20 Engines · Search M20B20 in the shop

Will the M20B20 engine fit my BMW E21 320i?

Yes, if your BMW E21 320i was built with the M20B20. BMW used this 2.0 liter (1,991 cc) petrol engine with 95 kW (129 HP) in the E21 320i from about 1977 to 1992.

In our records the M20B20 is the engine for the E21 320i, which makes the match simple. Still, check the code on your old engine or send us your VIN.

Also tell us if your E21 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all M20 Engines · Search M20B20 in the shop

Can I put an M54B30 engine in my BMW E30 320i?

Yes. We sell conversion kits that fit the M54B30 into the BMW E30 320i. The kit replaces the M20B25, M20B20 and M42, and works with the Getrag 260 and ZF S5D.

You can buy the full package with an engine, or only the parts you need: complete conversion with engine, complete conversion, adapter plate, engine mount, wiring and ecu and cooling and exhaust.

A swap like this needs a skilled workshop. Mounts, the adapter, the wiring and the engine computer, the cooling and the exhaust all have to work together. Check your local road rules for engine swaps before you start.

Tell us your BMW E30 320i's year and current set-up, and we suggest the right parts. You can reach the Hamburg desk by email at autowerkeengines@gmail.com, or by phone and WhatsApp on +49 15510 030835, Monday to Friday, 9:00 to 16:00 CET.

See all M54 E30 Conversion Kits · Conversion guide

Is the BMW M20B20 a diesel or petrol engine?

The M20B20 is a petrol engine. It is a 2.0 liter (1,991 cc) inline 6, SOHC, 12 valve unit with no turbo (naturally aspirated), and it was built to the Euro 1 emission standard.

The emission standard matters for registration and for low-emission zones in many cities. When you replace an engine with the same code, the car keeps the same paperwork and the same emission class.

Petrol versions need the correct catalytic converters and oxygen sensors on the car to stay legal and to keep the engine computer happy. Reuse the parts from your car if they are in good condition.

If you are not sure which version you need, send us your VIN. We tell you the right code for free.

See all M20 Engines · Search M20B20 in the shop

How long does delivery of an M20B20 engine take?

Orders confirmed before 14:00 CET on a working day leave Hamburg the same day. Later and weekend orders leave the next working day. Delivery to the Netherlands, Belgium, Germany, France, Luxembourg and Denmark takes 1 to 3 working days.

Spain, Italy, Portugal, Poland, Czechia, Austria, Ireland, the Nordics and the Baltics take 2 to 5 working days. Greek and Spanish islands, Malta, Cyprus and remote areas take 4 to 8 working days. The UK and other countries outside the EU are quoted one by one.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Every engine is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped, then photographed before it leaves the yard.

You get a tracking number when the pallet is collected. Check the wrapping before you sign, and note any damage on the paperwork.

See all M20 Engines · Search M20B20 in the shop

Will the M20B20 engine fit my BMW E21 320i?

Yes, if your BMW E21 320i was built with the M20B20. BMW used this 2.0 liter (1,991 cc) petrol engine with 95 kW (129 HP) in the E21 320i from about 1977 to 1992.

In our records the M20B20 is the engine for the E21 320i, which makes the match simple. Still, check the code on your old engine or send us your VIN.

Also tell us if your E21 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all M20 Engines · Search M20B20 in the shop

What should I replace when I fit a used M20B20 engine?

A used engine lasts longest when it starts life in your car with fresh fluids and new seals. Fit a new oil filter and fresh oil of the grade BMW lists for this engine, and refill the coolant with the correct BMW antifreeze mix. Change the drive belt, the thermostat and the water pump seals if they look tired, because they are cheap while the engine is out. Use new gaskets for the exhaust manifold, the intake and the sump plug, and check every hose clip before the first start.

Look at the engine mounts and the clutch or the torque converter while the engine is out. Old mounts can crack a new engine's brackets, and a worn clutch is much easier to change now.

Before the first start, turn the engine over without fuel until the oil pressure light goes out. Then let it idle, check for leaks, and drive gently for the first few hundred kilometres.

The warranty asks for fitting by a qualified mechanic and the correct oil, coolant and filters. Keep your receipts in case you ever need to make a claim.

See all M20 Engines · Search M20B20 in the shop

How do I know a used M20B20 engine is in good shape?

Each engine in the yard is inspected in Hamburg. The code is matched to the listing, the parts on the engine are recorded, the openings are sealed and the real unit is photographed. An inspection certificate for the unit can travel with the order when you ask for it.

When you look at a listing, check the recorded mileage, the year and the photos of the ports and the stamp. Ask for photos of anything you want to see closer. Ask the desk for more pictures of any listing. We are happy to show the stamp, the ports and the ancillaries before you decide.

On a petrol engine like the M20B20, a careful fitter will also look at the spark plugs, the coils and the timing side before the engine goes in.

If the engine fails inside under normal use, the warranty covers you. Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop.

See all M20 Engines · Search M20B20 in the shop

What comes with a used M20B20 engine?

Each M20B20 is sold as described on its own listing. The yard writes down the parts that are fitted to that unit, such as the turbo, the injectors, the manifolds or the alternator, so you know what arrives.

Some units are long engines with few ancillaries, others are more complete. If you need a part that is not listed, ask the desk. We often have the matching items in the yard.

Every engine is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped, then photographed before it leaves the yard.

On delivery, the carrier brings the pallet to the kerb or a loading bay. Please have a forklift, a pallet truck or an engine crane ready.

See all M20 Engines · Search M20B20 in the shop

Can you check if an M20B20 fits my car with my VIN?

Yes, and it is free. Send the 17-character VIN of your car and, if you have it, the gearbox code. We check the engine family, the build year window and the parts your car needs.

For the M20B20, we confirm that your car was built with this code or with a version that can take it. BMW used it in the BMW E30 320i, BMW E28 520i and BMW E21 320i.

We only reserve an engine once the match is confirmed, so you never pay for the wrong unit. You can reach the Hamburg desk by email at autowerkeengines@gmail.com, or by phone and WhatsApp on +49 15510 030835, Monday to Friday, 9:00 to 16:00 CET.

You can also use the VIN check on our site. It reads the year, the make, the model and the engine from the public vehicle register.

See all M20 Engines · Search M20B20 in the shop

Delivery, warranty and payment

Every 320i engine we sell is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped before it leaves Hamburg. You receive photographs of the packed engine and a tracking number.

Delivery is door to door and included in the price. Most European addresses receive the engine within five to ten working days; Germany and its neighbours are usually faster.

A 12-month warranty covers eligible internal failure when the engine is fitted by a qualified workshop with new fluids and filters. You can pay by card, bank transfer or crypto and receive the invoice by email straight away.

All E30 engines · M20 engine guide · BMW 320i engines for sale · Send us your VIN