"Is the 4 Serisi 420d reliable, and what should you check?"
When buying a used BMW 4 Series 420d 2016 (F32 / F33 / F36 / F82 / F83), the most frequently mentioned issue is carbon buildup in the EGR and intake ports. Timing chain stretching/wear (rarely reported) is also commonly noted.
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 and intake ports
Often reported
On 2.0 diesel units (B47 family), carbon deposits are reported in the EGR valve, EGR cooler, and intake ports; this can cause idle fluctuations, sluggish response, exhaust smoke, and occasional check engine light.
Engine Internal
Timing chain stretching/wear (rarely reported)
Often reported
The BMW 2.0 diesel engine family (especially the earlier N47) has a known history of timing chain stretching or premature wear. Although the B47 was designed to improve this, isolated reports exist.
Timing chain
DPF filter clogging
Often reported
On modern BMW 2.0 diesel engines, especially with city or short-distance driving, incomplete DPF regenerations and clogging issues can occur.
Exhaust Emissions
Fuel injection system / injector issues
Often reported
In some 2.0 diesel examples, problems with the common rail system (injectors or high-pressure pump) are reported, causing power loss, uneven distribution, smoke, and check engine light.
Fuel System
Turbo failure or wear
Often reported
Turbocharger failures or wear are reported on the 2.0 diesel: wastegate actuator issues, loss of boost pressure, or abnormal noises. Common causes include deposit buildup, hard driving, or inadequate maintenance.
Turbo
BMW 4 Serisi 420d technical specs
BMW 4 Serisi 420d (2016): 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 to look for when buying a BMW 4 Series 420d?+
When buying a 2016 420d, check the service history, test drive, and look for engine/transmission warnings. The most commonly reported issues are: carbon buildup in EGR and intake ports; timing chain stretching/wear (rarely reported); DPF filter clogging.
What are the common problems of the BMW 4 Series 420d?+
The most frequently reported issues are: carbon buildup in EGR and intake ports; timing chain stretching/wear (rarely reported); DPF filter clogging.
Is the BMW 4 Series 420d reliable?+
Rather than a simple yes/no, it's best to weigh 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 the Difetti fault database; the source vehicle is matched to the target vehicle by brand, fuel type, engine, and generation. Topics with insufficient evidence are not shown.