"Is the 4 Serisi 420d reliable, and what should you check?"
When buying a used BMW 4 Series 420d 2020 (F32 / F33 / F36 / F82 / F83), the most frequently mentioned issue is carbon buildup in the EGR valve and intake ports. Additionally, occasional problems with the timing chain/tensioner are also commonly reported.
Engine: B47
B47D20A · 420d · Used in this car from 2016-2021
Known engine issues
EGR valveMost problems of this engine are related to the EGR system, called AGR here. In early years, the valve could clog at 30,000 km and a recall campaign was even conducted. When it sticks open, overheating causes the intake manifold to crack.
Intake cloggingThe second most frequent service issue is clogging of the intake manifold and ports in the cylinder head, leading to loss of power and unstable engine operation. In severe cases, the intake swirl flaps may stick and break off.
Timing chain stretchThe chain timing drive on B-series engines differs little from N-series predecessors and may require attention before 200,000 km under very active use. There is already a cost-effective procedure to replace these chains without removing the engine.
+1 more issues on the engine detail page
Known issues and risks
Listed from most frequently reported, each with its source.
Carbon buildup in EGR valve and intake ports
Often reported
Carbon buildup in the EGR valve and intake ports is frequently reported on 2.0 diesel engines, causing knocking, sluggish throttle response, rough idle, and reduced performance. In severe cases, cleaning may be required.
Engine Bay
Occasional timing chain/tensioner issues
Often reported
Although timing chain stretching or wear has historically been associated more with older N47 engines, occasional reports also exist on some units or vehicles with newer 2.0 diesel engines (B47 family).
Timing chain
DPF clogging / frequent regenerations
Often reported
The diesel particulate filter (DPF) on the 2.0 diesel can clog, especially with city driving and low highway mileage, leading to frequent regenerations, power loss, and dashboard warnings.
Exhaust Emissions
Injector issues (wear or failure)
Often reported
Injector wear or failure can occur on common-rail diesel engines, causing hard starting, vibrations, power loss, and increased fuel consumption.
Fuel System
Turbo failure or wear
Often reported
Technical reports and user comments indicate turbo failure or degradation (including wastegate actuator issues or loss of boost pressure) resulting in torque/power loss, smoke, or abnormal noises.
Turbo
BMW 4 Serisi 420d technical specs
BMW 4 Serisi 420d (2020): boot 445 L; fuel use 4,5 l/100 km (urban 5,5 l/100 km · extra-urban 3,9 l/100 km); 0–100 in 7.3 s.
Boot capacity
445 L
Fuel consumption
4,5 l/100 km (urban 5,5 l/100 km · extra-urban 3,9 l/100 km)
What should I look for when buying a BMW 4 Series 420d?+
When buying a 2020 420d, check the service history, test drive, and look for engine/transmission warnings. The most commonly reported issues: carbon buildup in the EGR valve and intake ports; occasional timing chain/tensioner problems; DPF clogging / frequent regenerations.
What are the chronic problems of the BMW 4 Series 420d?+
The most commonly reported issues: carbon buildup in the EGR valve and intake ports; occasional timing chain/tensioner problems; DPF clogging / frequent regenerations.
Is the BMW 4 Series 420d reliable?+
Rather than a simple yes or no, it's necessary to evaluate the proven pros and cons together. This page lists 5 verified findings.
How does Carbeak collect data?+
The cards on this page are derived from Difetti fault database records; compatibility between the source vehicle and target vehicle is verified by brand, fuel type, engine, and generation. Topics with insufficient evidence are not displayed.