Used Mercedes-Benz SL-Class review and buying guide (2002 to 2008): which one to buy and what to check

Which used Mercedes-Benz SL-Class should you buy?

Go for a 2006 or later SL-Class. That's when Mercedes reworked the range with new engines, new gearboxes and sharper handling, and the revised cars are far better to drive. The pre-facelift 2002 to 2006 cars also carry a known fault: the electronic brake pump reaches its built-in limit and fails between 80,000 and 150,000 miles. Early cars come as the V6 SL350, the V8 SL500 or the SL55 AMG; later, the twin-turbo V12 SL600 sits at the top.

Don't treat a later car as trouble-free, though. Leaking roof seals and water in the boot turn up on 2006 and 2007 cars as well as early ones, and one owner's 2007 SL350 needed a new brake pump at 49,600 miles. Whichever year you pick, the state of the roof seals, the boot floor and the electrics should decide it, not the badge on the back.

If you're looking at a 2002 to 2004 car, it'll have been covered by two recalls: one for the electronic brake system, which could fail suddenly and leave the car on its hydraulic front brakes alone, and one to inspect the alternator's voltage regulator on the V6 and V8 petrols, replacing it where needed. Ask to see proof both jobs were done before you go any further with it.

Which SL-Class engines and gearboxes are the safe choices?

There's no engine to rule out on the evidence, but there's no clean bill of health either. One report filed against the SL describes early wear on the sprocket that drives the balance shaft in Mercedes' M272 and M273 V6 petrol engines, and fixing it is a big job. Ask the seller which engine the car has, and if it's one of those, whether the sprocket's been checked.

On an early SL350 or SL500, listen for a rattle from the fuel tank over bumps. The baffles inside it can break loose, and the only cure is a new tank, which means partly dismantling the folding roof to get at it. Any knocking from the back of the car on a rough road needs explaining before you hand over money.

The automatic gearbox is one of the places SL owners have run up big bills, alongside engine control unit faults. On the 2006-on V6 and V8 cars it's a seven-speed auto, so make sure it changes cleanly through every gear on the test drive, with no jerks or hesitation. Ask for receipts for any gearbox work, and don't accept a seller's line that a rough change is normal.

What should you check when viewing a used SL-Class?

Water getting in is the SL-Class's big weakness, so open the boot before anything else. Lift the floor and feel for damp, look for tide marks or rust, then run the roof through a full open and close cycle. The seals at the back of the roof, low on the rear pillars, fail on older cars and let water into the boot; one owner was quoted £2,349.60 to replace both.

A wet boot does real damage because pumps and electrics live in it. One owner of a 2006 car was charged £500 for a failed boot seal and £1,000 for the drowned pump behind it, and an SL55 AMG had its hydraulic central locking pump die twice in 8 months because the leak itself was never fixed. Try the central locking, the roof, the seat adjustment and the heated seats; if they only wake up after the engine's run for ten minutes, the auxiliary battery isn't holding its charge.

Don't shrug off an "electrics off line" or battery warning that clears after a few miles. It can mean the alternator's failing, and the electronic brakes could stop working. On a 2002 to 2006 car, a white service brake warning, or a red brakes defective warning with beeping, means the brake pump's worn out; ask whether it's been replaced. Watch for an ABC suspension warning too: one 2003 SL500 had a strut and then a pump replaced, and days later a front suspension rod snapped and that corner dropped.

Look around the starter battery tray. On one 2003 SL600, the pipe that carries acid away wasn't refitted after a battery change, and the tray and inner wing corroded so badly the repair was quoted at £7,000. Check the rear scuttle and the front edges of both rear wheel arch flanges for rust, which another 2003 car had, and ask for receipts for any roof seal or ABC suspension work.

Paste the advert into the free check and it runs these against the listing, the MOT history and the DVLA record before you travel.

What does a used Mercedes-Benz SL-Class cost to run?

What do SL-Class owners like about them?

The folding aluminium hard top is what makes the SL. With it up you've got a closed car with a proper solid roof, and with it stowed you're driving an open car. It's also about as much status as a car can give you, and that's a big part of why people want one.

There's no shortage of pace. The 2006-on SL500 is quick enough that you won't find yourself wanting more, and the V8 makes a lovely noise doing it. Drop the roof on a quiet road and that sound is half the reason to own one, which isn't something a spec sheet can tell you.

• The SL range received updates in 2006, including new engines, transmissions, enhanced handling, and improved interior trim.
• V6 and V8 models feature a 7G-TRONIC seven-speed automatic transmission as standard, with an optional Sport mode for faster shifts.
• The 2006 Mercedes-Benz SL-Class models, featuring increased engine power, are considered significantly improved vehicles overall.
• The 388hp 500SL engine provides ample speed and produces a pleasing sound.