BMW 8 Series 840d xDrive Gran Coupé common faults.

2019–2022, saloon, diesel, 320 HP.

The fault list covers: B57D30, B57D30T0 engine, ZF8HP70 transmission.

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3 fault write-ups. All are important. 6 recalls.

If you know the year, pick it. Faults for other years drop out of the list.

Before you buy

Known faults

3 important faults

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Diesel EGR cooler: cracking, coolant in the intake, fire risk

critical

The internal fins of the exhaust gas recirculation cooler crack over time, and glycol coolant leaks into the intake, where it mixes with soot. The sticky mixture can ignite at high temperature: it can melt the plastic intake manifold and, in extreme cases, cause an engine bay fire.

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The maker recalled the 2013 to 2018 four and six cylinder diesels, roughly 800,000 cars worldwide. The first repair attempt proved insufficient, and the leak returned in several cases: the cooler fitted since 2022, from a different supplier, is the valid fix.

So "the recall was carried out" is not enough on its own: you have to check when, and which repair was done. A first round repair does not by itself rule the problem out.

The early symptoms are white, sweet smelling exhaust smoke, slowly dropping coolant, and a rough idle.

It shows up on diesels built between 2013 and 2018. The earlier M57 is not covered by the recall.

between 108,000 and 222,000 km

What to check

Check the level in the expansion tank, and ask whether it has needed topping up
After a cold start watch the exhaust: persistent white smoke and a sweet smell mean the coolant is burning
Ask for the service book and find the EGR cooler recall entry: Check the date too

2 more steps in the write-up

B47 / B57 diesel: particulate filter and turbo on short trips

critical

The B47 replaced the N47, and the maker fixed the timing chain problem. The two remaining risks on this modern diesel depend on how the car was used.

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The first is the particulate filter. On short urban trips the regeneration cannot finish, and the filter clogs. The second is the turbo. With extended oil change intervals its bearings wear.

On this engine the service history and the type of use tell you more than the odometer. On a 200,000 km car driven on motorways and serviced often, the filter and the turbo can be in better shape than on a 90,000 km city-only car.

Where turbo wear leads in the worst case: a runaway engine. If the turbo shaft seal fails, engine oil enters the intake on the compressor side. A diesel burns that too, and this is different from a petrol engine: a diesel controls torque with the quantity of fuel injected, and it has no throttle. Once the engine runs on its own oil, cutting the injection and switching off the ignition will not stop it. The revs climb on their own until the engine destroys itself for lack of lubrication.

If this happens while driving, turning the key does not help. The only thing that works is cutting off the air: cover or plug the intake, or discharge a dry powder extinguisher into the intake tract. On a manual car you can also stall it: hold the parking brake and the brake pedal, select a high gear, and release the clutch quickly so the drivetrain chokes the engine.

This is not common, and it can happen on any turbo diesel, not only on this engine. On this engine the turbo bearing and seal wear. The warning signs are blue smoke under acceleration, an unexplained drop in oil level, and an oily charge air pipe.

What to check

Ask how the car was used: short daily trips or longer runs?
Read the fault codes for particulate filter regeneration and differential pressure
On a longer test drive watch the power delivery and the smoke under load

5 more steps in the write-up

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ZF 8HP automatic: mechatronics unit and connector sleeve leak

expensive

The ZF eight speed automatic (BMW Steptronic 8HP family) has two faults, and you can feel both.

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The first is the mechatronics unit: the valve body and the control electronics in one. If the solenoids or the pressure regulation weaken, the gearbox jerks, the D/R engagement is delayed, it logs a gear ratio fault code, and finally drops into limp mode (often staying in 2nd or 3rd).

The second, and often misdiagnosed, is the connector sleeve of the mechatronics unit: the O-ring of the plastic sleeve ages, and ATF leaks from the side of the housing, exactly where the wiring harness enters. This is easy to mistake for a rear crankshaft seal. The trail starts from the driver's side of the housing, not from the clutch side.

On cars built in 2023 there was also a separate safety recall for a welding fault in the mechatronics unit. That is not the same as the wear related sleeve and the valves.

Check the fluid level, the area around the sleeve and the fault codes first; do not accept a "full gearbox replacement" quote straight away.

above 120,000 km

What to check

On the test drive watch for delayed D/R engagement, a jerk when shifting, and limp mode (a stuck gear)
Look at the driver's side of the gearbox housing where the wiring harness enters: an ATF trail from the sleeve is suspect
Do not confuse it with a rear crankshaft seal leak: the direction of the trail decides

3 more steps in the write-up

Official recall6 recallsShow

The manufacturer fixes these for free at a franchised dealer. Ask with the VIN whether it was done.

A12/00184/24Safety recallInjuriesno date · EU Safety Gate

Due to a manufacturing error, the weld seam of the integrated transmission control unit (ITCU) may not have been correctly executed. As a result, transmission oil could leak into the ITCU, causing it to fail. This may lead to transmission seizure, increasing the risk of an accident. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.