Models · Audi
Audi S4 B9 buying guide
The B9 S4 was sold from 2016 as a saloon and Avant, first with a 3.0 TFSI turbocharged V6 petrol and, from 2019 in the UK, with a 3.0 TDI V6 diesel. Both use an 8-speed automatic and quattro four-wheel drive, and both are fast, refined everyday cars.
The versions
- 3.0 TFSI turbocharged V6 petrol (EA839), 354PS, 2016 to 2019
- 3.0 TDI V6 diesel, 347PS and 700Nm, from 2019, with a 48-volt mild hybrid system and an electric compressor to sharpen response
- 8-speed Tiptronic torque converter automatic, replacing the previous S tronic
- Permanent quattro four-wheel drive, with a sport differential on some cars
- Saloon and Avant bodies
What to check on a B9 S4
3 model-specific things to look at when you view one. They're a starting point, not the full inspection.
Petrol: the water pump
What to look for: With the bonnet open, look at the pulley on the front of the engine that drives the water pump. Count its bolts: six means the revised pump, four means the original. Check the coolant tank is between its marks and look for dried coolant residue on the front of the engine and around the cylinder heads.
Why it matters: The original pump on the EA839 petrol V6 can leak internally, and coolant can be drawn into the engine's vacuum system, where it can trigger a boost fault warning and in time cause damage. Audi released a revised pump with a six-bolt pulley. A car with the later pump fitted has had this dealt with.
Petrol: oil use and the breather
What to look for: Ask how much oil the car uses between services and check the level on the dashboard display. Look for oily residue around the oil filler cap, and for blue smoke on a cold start or hard acceleration.
Why it matters: The crankcase breather (PCV) valve is built into the cam cover on this engine, and its diaphragm can split, pushing oil into the intake and raising consumption. The fix is a replacement cam cover with the new valve. It's a known item rather than a sign of a worn engine.
Gearbox changes and fluid
What to look for: From cold, move from park to drive and reverse and note any delay before it engages. Drive gently through the first few gears, then at low speed in traffic. Changes should be smooth, with no harsh 1 to 2 shift and no shudder at low speed. Ask whether the gearbox oil has ever been changed.
Why it matters: The ZF 8-speed automatic is strong, but its fluid ages, and specialists recommend changing it rather than treating it as lifetime fill. Harsh or delayed changes are the usual sign that it's due, and a gearbox service often improves them.
Also in the full guide
- Rear differential noise
- Diesel: particulate filter and AdBlue
- Front suspension arms
- The cold start, test drive and paperwork checks for the exact version you're viewing
The full guide to the B9 S4
The CrankSight guide walks you round the car on your phone at the viewing, with every check for the exact version you're looking at: what to look for, where to find it, and what anything you find is likely to cost. As you go it builds an assessment of that car, and if you view more than one, it lines them up side by side.
£29 for the model, used on as many cars as you like, delivered within 72 hours or your money back.
Other generations
General points for the model, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with Audi.