KNOWN FAULTS · BMW

BMW Serie 4 (G22/G23/G26) 420d (B47) common problems.

2020–2026 · Diesel

Sources are not verified in real time and no entry confirms that your car is affected.

3 known faults with sources

B-engine coolant leaks and EGR coolerCooling / EGR

Engine / equipment: B47 and B57 diesel and B48 and B58 petrol modular engines (BMW from 2014–2015 and MINI from 2014)
Period mentioned: 2014–2026
Symptoms: Coolant loss with a low-level warning, coolant or oil residue at the rear of the engine; on diesels, internal coolant loss with no visible leak (EGR cooler).
Possible cause described: On the B48 and B58 the water pump leaks (from its weep hole) and the oil filter housing with heat exchanger can crack; on 2017–2021 B58s the crankcase ventilation valve also fails. On the diesels the EGR cooler can leak internally and mix coolant with soot: BMW issued a recall over the risk of the intake manifold catching fire.
Check for the garage: Check the coolant level, look for leaks under the water pump and at the oil filter housing, and on diesels confirm by VIN whether the EGR cooler campaign was done.
Cost cited in the source: Water pump: relatively cheap to replace; oil filter housing: more labour-intensive; EGR cooler: free if covered by the campaignA rough figure from the original database, not an up-to-date quote.

Mileage cited in the database: 80,000–195,000 km. This is not a maintenance interval and does not predict a failure.

Applies if: Only if fitted with the automatic gearbox described in the record.

ZF 8HP oil level, leaks and harsh shiftsAutomatic gearbox

Engine / equipment: ZF 8HP automatic gearbox in rear-wheel-drive BMWs from 2009 (1 to 8 Series and X: F20, F30, F10, G20, G30, X3, X5…)
Period mentioned: 2009–2026
Symptoms: Harsh shifts (especially engaging D and 1st to 2nd), slipping or jerking; oil leaks from the pan, the mechatronic connector sleeve or the seals.
Possible cause described: BMW's diagnostic guide says an incorrect oil level is a frequent cause of shift complaints and asks for it to be checked every time, even with no visible leaks; the pan can be damaged by impacts. The sealing sleeve between gearbox and mechatronic lets oil through to the connector. The oil, sold as lifetime, degrades.
Check for the garage: Check the oil level with the official procedure (correct temperature and engine running), look for leaks at the pan, connector sleeve and seals, inspect the pan for impact damage and review adaptation values with ISTA.
Cost cited in the source: Oil change with pan and filter: maintenance; sleeve or seals: minor repair; mechatronic: expensive repairA rough figure from the original database, not an up-to-date quote.

Applies if: US bulletin SIB 64 06 26: only the 4 Series Gran Coupé (G26).

Whistling from the centre console with the climate control, caused by a displaced foam seal (4 Series Gran Coupé and i4)Climate control

Engine / equipment: BMW 4 Series Gran Coupé (G26) and i4
Period mentioned: 2024 (US model years)
Symptoms: Whistling from the centre console or dashboard with the climate control fan at speed 2 or above; it goes away at full speed and is louder with the rear console vents closed, near the phone charging tray.
Possible cause described: The grey foam seal that joins the dashboard climate unit to the centre console ducts is out of position. BMW says to replace it (bulletin SIB 64 06 26).
Check for the garage: Check whether the whistle changes when you open and close the rear console vents with the fan at speed 2; if so, ask the garage to inspect that seal.
Cost cited in the source: No verified estimate; ask the garage for a quote.A rough figure from the original database, not an up-to-date quote.