Audi S4
Supercharged V6 with 260 kW. Proven drivetrain for S4/S5 and SQ5 with linear power delivery and good throttle response.
354 hp company car — objectively fast, subjectively empty
Fast, quiet, completely sterile. Active Sound from the speakers instead of real V6 noise, steering that informs but never communicates, AWD that delivers traction without ever being noticed. Objectively better than the B7 at everything except making you feel something. The right car for a fast commute — the wrong car for a driving experience.
Engine Weaknesses 8
Early CWGD units with P-code GP0 (up to production date 06.08.2018) have poor-quality rocker arm rollers. The small bearing rollers can fall out and end up in the oil sump — camshaft and piston damage possible.
Symptoms: Combustion misfire, engine fault light, rough running, clattering noise from cylinder head.
The EA839 water pump is vacuum-controlled. On internal failure, coolant enters the vacuum system and spreads to further engine components. The old 4-bolt pulley is the prime suspect — identifiable if original pump still fitted.
Symptoms: Coolant warning light, coolant loss without external leakage, P0299 (boost pressure too low), 'drivetrain fault', 12V battery no longer charging.
The belt starter-generator (BSG) and the 48V battery can fail, especially on vehicles before 2021 without the protective cover over the control unit. Diagnosis and calibration required after replacement.
Symptoms: '48V system fault' in display, start-stop disabled, no recuperation, rough or delayed starting, limp mode.
Beyond water pump failure, EA839 engines also show coolant loss from seal failures elsewhere in the cooling system. Regular coolant level checks important.
Symptoms: Coolant level drops without visible leakage, overheating warning, coolant smell in engine bay.
Turbocharged version of the EA839 without supercharger, but still direct injection: oil mist from crankcase ventilation settles as coke on intake valves.
Symptoms: Hesitation, power loss at part throttle, cold-start problems, rough idle.
The EA839 CWGD shows elevated oil consumption during spirited driving and high revs from piston rings. Vehicles frequently on track or driven at full throttle are particularly affected.
Symptoms: Regular top-ups required, oil consumption above 0.5 L/1,000 km during spirited use.
The EA839 CWGD responds to worn spark plugs with misfires and elevated fuel consumption. Change interval of 30,000–40,000 km recommended for spirited use.
Symptoms: Hesitation under load, misfire fault codes, increased consumption, slight power loss.
Excessive manufacturing tolerances between injector lines and rail cause petrol vapour leaks. Fuel smell inside the car is the typical symptom.
Symptoms: Petrol smell inside after switching off, especially with a warm engine.
Vehicle Weaknesses 15
Recall 42L1/42L5: Stress corrosion cracking in the rear trailing arm can increase play. Affected: build years 2019–2021. Missing wheel alignment after the initial recall caused severe rear tyre wear.
Recall 74E3 for S4 B9 (build years 2018–2020): a seat heater wiring fault can cause an occupancy sensor error and deactivate the front passenger airbag.
The Virtual Cockpit freezes or shows only the speedometer and tachometer during driving. The problem recurs even after software updates. A full digital cockpit replacement is expensive.
At higher mileages, worn wheel bearings and failed ball joints are documented. MOT testers regularly flag suspension geometry faults. Repair including wheel alignment costs around €800–1,500.
The optional electronically controlled suspension shows sporadic fault messages and damper failures. A single adaptive damper costs €500 net and upwards.
The S4 B9 TDI suffers from a software-related hesitation on pull-away: the engine revs to 2,000–2,500 rpm with no forward movement, then power arrives abruptly. Caused by WLTP gearbox calibration. Reduced in Dynamic mode.
The B9 develops coolant leaks from flanges in the cooling circuit. Plastic weld seams can crack — in severe cases overheating is a risk.
On the S4 B9 TDI, AdBlue injector nozzles can block through crystallisation or the urea pump can fail. After a fault message, a countdown to engine lock-out begins.
The S4 B9 shows increased brake disc wear during spirited driving. A complete front-and-rear set in OEM quality costs around €900–2,750.
The MMI system frequently has problems with Bluetooth, CarPlay and online connectivity. A software update is often sufficient, but occasionally a control unit swap is needed.
The ZF 8HP torque-converter automatic shows delayed shifting and judder on pull-away when cold. Audi sometimes describes this as 'state of the art'. A gearbox oil change can help.
On the optional panoramic roof, water drain channels can block or hoses detach, allowing water into the footwell or down the A-pillar.
The optional B&O premium sound system is prone to sporadic audio cut-outs due to control unit software errors. Voltage drops in cold conditions can crash the chip.
Rear wheel bearings on the S4 B9 can wear prematurely — accelerated by spirited driving and the quattro all-wheel-drive system. Cases documented below 80,000 km.
Annoying creaks and rattles in the dashboard and door panel area, sometimes occurring after only a short time. Workshop visits often provide no lasting fix.