The BMW 850i in the 8 Series generation (E31, built 1989–1999) was built with one engine, the M70B50: a 5.0 L petrol V12 with 300 hp.
This guide tells you which engine your 850i has, what goes wrong with it, what a replacement costs from our stock and what else to plan for when you fit one.
- Generation: 8 Series, 1989–1999
- Body styles: E31 (coupé)
- Engines: M70B50
- Output: 300 hp
- Replacement engines in stock: ask the desk for the next arrival
Which engine is in your 850i?
| Engine code | Built | Power | Torque | Type |
|---|---|---|---|---|
| M70B50 | 1987–1994 | 300 hp | 450 Nm | 5.0 L petrol V12, naturally aspirated |
M70B50 in the 850i
The M70B50 was used in the E31 850i, built 1987–1994. It is a 5.0 L naturally aspirated petrol V12 with 300 hp and 450 Nm.
Reading the code: M marks an M-series code, the naming BMW used for its engine families up to the early 2000s; 70 is the family number; B stands for petrol (from the German Benzin); 50 is the capacity in decilitres, so 5.0 litres.
850i engines by model year
| Model year | Engine |
|---|---|
| 1989 | M70B50 (300 hp) |
| 1990 | M70B50 (300 hp) |
| 1991 | M70B50 (300 hp) |
| 1992 | M70B50 (300 hp) |
| 1993 | M70B50 (300 hp) |
| 1994 | M70B50 (300 hp) |
The 850i kept the same engine for the whole E31 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 850i
A replacement engine does not have to come from another 850i. 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.
M70B50: BMW E32 750i.
How to confirm your engine code
The 850i only used the M70B50, 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 850i engine problems
The M70B50 in the 850i shares the known weak points of the M70 and M73 family. Full M70 and M73 guide.
| Known fault | What to check |
|---|---|
| Wiring harness | Inspect the harness near the heads. |
| Cooling | Pressure-test the system. |
| Dual engine management | Read both ECUs for fault codes. |
| Fuel system | Check fuel pressure. |
Wiring harness. Harness insulation becomes brittle with heat and age.
Cooling. Radiators, hoses and fan clutches fail with age.
Dual engine management. A fault on one bank's management system causes rough running.
Fuel system. Fuel pumps, pressure regulators and injectors age.
Symptoms to watch for on the 850i
Rattle for a few seconds after a cold start. The classic sign of a weak timing chain tensioner or stretched chain. It must be checked quickly: a chain that jumps a tooth can bend valves.
Looking after the 850i engine
- Oil: 5W-40 or 10W-40 synthetic, about 7.5 litres.
- Service interval: Oil every 10,000 km or yearly.
- Timing drive: Single-row timing chains, one per bank.
- Workshop notes: Keep the cooling system fresh. Check both ECUs before purchase.
Buying a used engine for the 850i: checklist
- 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.
- Warranty terms in writing. Read what the warranty covers, how long it runs and what fitting conditions apply. Most warranties require a qualified workshop, new fluids and filters, and replacement of the cooling parts that caused the original failure.
- 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.
- Confirm the exact engine code. Read the code stamped on the block and compare it with the code for your car. Send us the last seven characters of the VIN and we confirm the match before anything is paid.
- 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.
- Timing chain noise. Listen for a rattle at the front of the engine for the first seconds after a cold start. On an engine that cannot be run, look at the chain guides through the oil filler or with the valve cover off.
- 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.
- Both cylinder banks and both ECUs. V12 engines often use separate management for each bank. Read faults from both and compare compression across all twelve cylinders.
BMW 850i replacement engine cost
We do not have a 850i 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 850i?
Engine swaps and upgrades for the 850i
These engines were fitted to other versions of the E31 at the factory, which makes them the most practical upgrades: the body was designed around them and many parts are shared.
| Engine | Factory model | Power | Gain |
|---|---|---|---|
| M73B54 | E31 850Ci | 326 hp | +26 hp |
Can I fit the M73B54 in my 850i?
Yes, it is one of the more common upgrades. Both are petrol V12 engines, so the mounting points are similar, but the M73B54 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 26 hp and 40 Nm. In Germany and most of Europe an engine swap must be inspected and registered.
Fitting a replacement engine in the 850i
- Inspect or replace the timing chain parts. Look at the guides and tensioner. On high-mileage engines, replacing them now costs far less than doing it later.
- 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.
- 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.
- 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.
- 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.
850i engine questions
Will the M70B50 engine fit my BMW E31 850i?
Yes, if your BMW E31 850i was built with the M70B50. BMW used this 5.0 liter (4,988 cc) petrol engine with 220 kW (300 HP) in the E31 850i from about 1987 to 1994.
In our records the M70B50 is the engine for the E31 850i, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your E31 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 M70 Engines · Search M70B50 in the shop
What is the BMW M70B50 engine?
The BMW M70B50 is a 5.0 liter (4,988 cc) petrol engine from the M70 family. It has a V12, SOHC, 24 valve layout with no turbo (naturally aspirated), and makes 220 kW (300 HP) with 450 Nm of torque. BMW built it from 1987 to 1994 and it meets the Euro 1 emission standard.
You find the M70B50 in the BMW E32 750i and BMW E31 850i. What we list: BMW M70 5.0 V12 engines for the E32 750i and E31 850i.
At Autowerke Engines every M70B50 is a real used engine from our yard in Hamburg. Before a unit is listed, the yard checks the engine code against the listing, writes down the parts fitted to it, seals every opening and photographs the real engine you will receive. Each listing shows the year, the mileage and the price, so you can compare units side by side.
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 M70 Engines · Search M70B50 in the shop
Are there other versions of the BMW M70B50?
In our yard the M70B50 is the only listed version of the M70 family. It makes 220 kW (300 HP) and 450 Nm, and was built from 1987 to 1994.
Engines in one family share a basic block, but the turbo, the injection, the sensors and the engine computer can differ. A higher power version often has different pistons, a bigger turbo or a different fuel system.
This is why we ask for the exact code. Fitting a different version can work, but the wiring, the software and sometimes the gearbox must be changed to match.
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 M70 Engines · Search M70B50 in the shop
Does a used M70B50 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 M70 Engines · Search M70B50 in the shop
Will the M70B50 engine fit my BMW E31 850i?
Yes, if your BMW E31 850i was built with the M70B50. BMW used this 5.0 liter (4,988 cc) petrol engine with 220 kW (300 HP) in the E31 850i from about 1987 to 1994.
In our records the M70B50 is the engine for the E31 850i, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your E31 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 M70 Engines · Search M70B50 in the shop
How long does delivery of an M70B50 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 M70 Engines · Search M70B50 in the shop
How much power and torque does the BMW M70B50 have?
From the factory the BMW M70B50 makes 220 kW (300 HP) and 450 Nm of torque. It is a 5.0 liter (4,988 cc) V12, SOHC, 24 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 M70B50 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 M70 Engines · Search M70B50 in the shop
How much does a used BMW M70B50 engine cost?
A used BMW M70B50 engine in our yard usually costs between 3.850 € and 5.950 €. The exact price depends on the year, the mileage and the parts that come with the engine.
Our units show recorded mileage from about 22,000 km up to around 200,000 km. Lower mileage and more ancillaries mean a higher price. Each listing shows its own price, and the price you see is the price you pay. Prices include VAT for private buyers.
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. If you order a gearbox or a second engine on the same order, the fee is still charged once.
Inside the EU there is no import duty. For the UK and other non-EU countries, import duty and local VAT are paid by the receiver, and we supply a commercial invoice.
See all M70 Engines · Search M70B50 in the shop
Can you check if an M70B50 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 M70B50, we confirm that your car was built with this code or with a version that can take it. BMW used it in the BMW E32 750i and BMW E31 850i.
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 M70 Engines · Search M70B50 in the shop
What should I replace when I fit a used M70B50 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. Check the spark plugs and the ignition coils, and make sure the fuel lines are clean and tight before you crank the engine. Change the drive belt, the thermostat and the water pump seals if they look tired, because they are cheap while the engine is out.
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 M70 Engines · Search M70B50 in the shop
Delivery, warranty and payment
Before a 850i 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.
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.
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 E31 engines · M70 and M73 engine guide · Send us your VIN
