"Is the 3 Serisi 340i reliable, and what should you check?"
When buying a used BMW 3 Series 340i 2018 (F30 / F31 / F34 / F80 / LCI), the most commonly reported issue is oil leaks from the filter housing, valve cover, and various gaskets. Coolant consumption/heating and cooling system leaks are also frequently reported.
Engine: B58
B58B30A · 340i · Used in this car from 2015-2019
Known engine issues
Crankcase ventilationFirst-generation units had a short-lived crankcase ventilation valve, whose membrane wore out quickly, causing white smoke from the exhaust. Later the PCV design was revised and this problem became less common.
Oil pumpSecond-generation B58TU engines were equipped with a problematic version of the oil pump with a plastic adjustment ring that could crack even at low mileage. Then oil pressure dropped and a corresponding error appeared on the dashboard.
Coolant leaksThe most common cause of B58 engine failure is low coolant level, so it is extremely important to monitor leaks and replace the coolant reservoir cap every two years. If a coolant level error appears, you must go on a tow truck.
+1 more issues on the engine detail page
Known issues and risks
Listed from most frequently reported, each with its source.
Oil leaks from filter housing, valve cover, and various gaskets
Often reported
Many B58 owners report oil leaks from the oil filter housing, sump gaskets, valve cover, and PCV system. The filter housing gasket often hardens and leaks, causing oil loss. Valve cover and PCV gaskets and membranes deteriorate over time, leading to leaks, burnt oil smell, coil contamination, and sometimes warning lights or misfires.
Engine Bay
Coolant consumption/heating and cooling system leaks
Often reported
Some B58 engines report coolant consumption not always accompanied by visible external leaks. Common causes include plastic components of the system (caps, fittings, expansion tank) or failing electric pumps/thermostats.
Cooling
VANOS solenoids and variable timing issues
Often reported
VANOS solenoid failures have been reported on the B58 engine, causing idle fluctuation, low-end torque loss, and warning lights. Possible causes include oil blockage or worn O-rings.
Engine Internal
Turbo / Wastegate Issues (Noises, Boost Loss)
Often reported
Turbo
BMW 3 Serisi 340i technical specs
BMW 3 Serisi 340i (2018): boot 480 L; fuel use 7,4 l/100 km (urban 10 l/100 km · extra-urban 5,9 l/100 km); 0–100 in 5.2 s.
Boot capacity
480 L
Fuel consumption
7,4 l/100 km (urban 10 l/100 km · extra-urban 5,9 l/100 km)
What to look for when buying a BMW 3 Series 340i?+
When buying a 2018 340i, check the service history, perform a test drive, and inspect engine/transmission warnings. Most commonly reported issues: oil leaks from filter housing, valve cover, and various gaskets; coolant consumption/heating and cooling system leaks; VANOS solenoids and variable timing problems.
What are the common problems of BMW 3 Series 340i?+
Most frequently reported issues: oil leaks from filter housing, valve cover, and various gaskets; coolant consumption/heating and cooling system leaks; VANOS solenoids and variable timing problems.
Is the BMW 3 Series 340i reliable?+
Instead of a simple yes/no, it's better to weigh the proven pros and cons together. This page lists 4 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, engine, and generation. Topics with insufficient evidence are not shown.