BMW 520i (E28) engine: which one, problems and replacement

The BMW 520i in the second 5 Series generation (E28, built 1981–1988) 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 520i, the faults to look for, current prices for a replacement and the swap options that make sense.

• Generation: second 5 Series, 1981–1988
• Body styles: E28 (saloon)
• Engines: M20B20
• Output: 129 hp
• Replacement engines in stock: ask the desk for the next arrival

Which engine is in your 520i?

M20B20 in the 520i

The M20B20 was used in the E28 520i, 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.

520i engines by model year

The 520i kept the same engine for the whole E28 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 520i

A replacement engine does not have to come from another 520i. 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 E30 320i, BMW E34 520i.

How to confirm your engine code

The 520i 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 520i engine problems

The M20B20 in the 520i 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 520i

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 520i 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 520i: checklist

1. 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.
2. List of what is fitted. Engines are sold with different ancillaries: some have the turbo, injectors, manifolds, alternator and starter, others are long blocks. Agree the list in writing so you know which parts must come from your old engine.
3. Ask how the donor car was damaged. Most good used engines come from cars with body damage. A front-end impact can crack sensors, the timing cover or the sump; a rear or side impact usually leaves the engine untouched. The yard records the damage on each unit.
4. 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.
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 520i replacement engine cost

We do not have a 520i 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 520i?

Engine swaps and upgrades for the 520i

These engines were fitted to other versions of the E28 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 M30B25 in my 520i?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M30B25 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 21 hp and 51 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the M30B28 in my 520i?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M30B28 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 55 hp and 76 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the M30B32 in my 520i?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M30B32 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 68 hp and 121 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Fitting a replacement engine in the 520i

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.

520i engine questions

Will the M20B20 engine fit my BMW E28 520i?

Yes, if your BMW E28 520i was built with the M20B20. BMW used this 2.0 liter (1,991 cc) petrol engine with 95 kW (129 HP) in the E28 520i from about 1977 to 1992.

In our records the M20B20 is the engine for the E28 520i, which makes the match simple. Still, check the code on your old engine or send us your VIN.

Also tell us if your E28 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

How much is a replacement M20B20 engine for a BMW E28 520i?

A used M20B20 for the BMW E28 520i 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 E28 520i?

Yes, if your BMW E28 520i was built with the M20B20. BMW used this 2.0 liter (1,991 cc) petrol engine with 95 kW (129 HP) in the E28 520i from about 1977 to 1992.

In our records the M20B20 is the engine for the E28 520i, which makes the match simple. Still, check the code on your old engine or send us your VIN.

Also tell us if your E28 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

Does a used M20B20 engine come with a warranty?

Yes. 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.

The warranty does not cover damage from wrong fitting, overheating, low oil, wrong fluids or fuel, engines that were opened or modified without our approval, or labour and towing costs.

To claim, send us your order number, a short description of the problem, photos or a video, and a mechanic's report if we ask for one. If the claim is approved, we repair, replace or refund the engine.

Keep the receipts for the fitting, the oil and the filters. They make any claim quick and simple.

See all M20 Engines · Search M20B20 in the shop

How much is a replacement M20B20 engine for a BMW E28 520i?

A used M20B20 for the BMW E28 520i 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

Which cars use the BMW M20B20 engine?

BMW fitted the M20B20 to the BMW E30 320i, BMW E28 520i and BMW E21 320i. These cars were built with this engine from about 1977 to 1992.

The badge on the boot is not enough to be sure. The same model name can hide two different engines, for example after a facelift or a change in emission rules. Always read the engine code stamped on the block, or look it up with your VIN.

Other engines in the same M20 family are the M20B25 (171 HP). They look alike but differ in power, parts and electronics, so they are not always a direct swap.

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

How much power and torque does the BMW M20B20 have?

From the factory the BMW M20B20 makes 95 kW (129 HP) and 174 Nm of torque. It is a 2.0 liter (1,991 cc) inline 6, SOHC, 12 valve petrol engine with no turbo (naturally aspirated).

Without a turbo, the power builds smoothly with the revs. A clean air intake, healthy ignition and the correct fuel are key to getting the full figure.

A used engine reaches its factory numbers when it is fitted with the matching engine computer and software, and serviced with the right oil and filters. If the engine computer from your car is a different version, a specialist may need to code it.

Every M20B20 on our site lists its year and mileage. Ask the desk for more pictures of any listing. We are happy to show the stamp, the ports and the ancillaries before you decide.

See all M20 Engines · Search M20B20 in the shop

Delivery, warranty and payment

Before a 520i engine leaves our Hamburg yard it is drained of oil and coolant, every opening is sealed, and it is strapped to a pallet and wrapped. We send photographs of the packed unit and the tracking details.

Door-to-door delivery is included to the address you give at checkout. Typical delivery takes three to five working days within Germany and neighbouring countries and five to ten working days to the rest of Europe and the UK.

Every engine carries a 12-month warranty on eligible internal failure when a qualified workshop fits it with new fluids and filters. Payment is by card, bank transfer or crypto; your invoice is emailed as soon as you order.

All E28 engines · M20 engine guide · BMW 520i engines for sale · Send us your VIN