Used car buying guide: Audi RS6 (C5)

The gearbox is another story. Torque-converter failures plague the otherwise promising reputation of the C5’s powertrain and can cost you big money. A full rebuild will set you back around £3000, or you can have a new unit for £5000 plus shipping from the US.

All of which is to say: walk away from any car that doesn’t have a full service history, preferably from a combination of main dealer and Audi specialists, be aware of the C5’s most expensive potential pitfalls from the outset and set aside a hefty rainy-day fund for future repairs.

How to get one in your garage

An owner's view

Adam Broadway: “It’s not a cheap car to run. Don’t think of it as an Audi: think of it as a supercar, because that’s what it is – and because of that, everything costs a lot of money! Look for one that’s just had the gearbox done over one with low mileage that hasn’t. They eat tyres and brakes – discs are £500 each – and if you do buy one, take it straight to a specialist to get it checked over. Get ready for a bill as there will always be something wrong.”

Buyer beware...

â–  Engine: If you can stomach its sub-20mpg fuel economy, the V8 is a rather amiable beast to live with. The timing belt should be changed every 35,000 miles and the cambelt at 40,000, and it makes sense to replace the cam chain tensioner, O2 sensor, voltage regulator, camshaft positioning sensor and starter assembly while the front clip is off. Check previous owners have been judicious in this regard. Intercoolers can leak, leading to turbo failure.

â–  Suspension: It’s a question of when, not if, the Dynamic Ride Control system will start leaking. A popular fix is to replace the struts with conventional coilovers from brands like Koni, Bilstein and KW, so check the quality of any aftermarket components used. If the original system is still in place, keep an eye out for fluid around the top of the shocks.

â–  Gearbox: The torque converter is prone to complete failure at high mileages (expensive). Symptoms include clunky shifts, erratic revving and disengaging under acceleration. Some owners have had success with a simple fluid change.

â–  Interior: Most switches, buttons and trim elements are taken from the standard A6, so they’re durable and easy to replace. Instrument cluster loses pixels over time, but replacement LCD panels and second-hand units are easy to source. It’s a good idea to check the stereo, seats, climate control and windows all work as expected.

â–  Body: Water gets into the cabin when the bulkhead drain hole is blocked or the pollen filter seal is perished, so check for wet carpets. Scour the entire car for signs of accident damage, poor paint jobs and surface rust.

â–  Electrics: A more serious consequence of blocked drain holes is corrosion to the main fuses, which are hidden behind the coolant expansion tank.

Also worth knowing

If 444bhp isn’t quite enough for you and your family, you could try to track down an elusive RS6 Plus edition. Launched in 2004 as a low-volume run-out special, the Plus had an extra 29bhp, lower suspension and cross-drilled brakes. Just 999 were built. Expect to pay upwards of £25,000.

How much to spend

£7500-8999: High-milers with cosmetic issues and electrical niggles.

£9000-£11,999: Well-optioned and well-used cars, mostly with a bundle of service history.

£12,000-£19,999: Late C5s with stacks of documentation and attractive upgrades.

£20,000 and above: Immaculately presented with low miles.

One we found