Mercedes Service and Repair Redwood City - Mercedes SL55 Buying Guide - Bosch European Redwood City 650-368-3000

One of the best of the breed is the one you see here and, with the weather taking a turn for the sunny, perhaps the time to consider taking the plunge.

The SL55 AMG was the most powerful road car ever built by Mercedes when it was launched in 2002 and, clearly, one of the most worthy SLs ever. It arrived in the summer of that year, following on from the R230 SL500 on which it was based, with 476hp from its 5.4-litre supercharged V8. The SL55 covered 0-62mph in 4.7 seconds and had an electronically capped top speed of 155mph.

There was immediate speculation about the SL55's true top speed from the moment it was launched. To prove the car's potential, one German car magazine removed the electronic limiter and drove an otherwise standard SL55 to 202mph. However, all UK-spec SL55s come with a speedo reading up to 180mph.

The SL55 AMG proved an immediate hit with UK buyers and the AMG accounted for as many as one in four SL sales between 2002 and the less-than-fortunate facelift of 2008. Power was soon upped to 500hp to prevent the similarly engine E55 outgunning the flagship SL, a further round of revisions in 2006 increasing power further to 517hp thanks to a new higher speed pulley for the supercharger and larger throttle valve.

When Mercedes brought in its revised styling for the SL in 2008, it took the chance to drop the M113 5.4-litre V8 and replace it with the M156 6.2-litre V8 to create the SL63. For this guide, we'll stick with the M113-powered SL55 that is far more plentiful and popular.

Powertrain

The SL55 AMG's 5.4-litre V8 may have been based on the SL500's, but very little of the less powerful, non-supercharged motor remains untouched. For starters, there's the belt-driven screw-style supercharger that sits in the vee of the engine block. With Teflon-coated aluminum screws, the supercharger can spin at up to 23,000rpm when the engine is at its limit. This rev limit for the engine is increased to 6,100rpm from the standard SL500's 5,600rpm ceiling.

To cope with this extra power and its associated stresses, AMG engineers adapted the crankcase to use special transverse screws. The engine also runs with a strengthened block, uprated bearings and pistons with greater resistance to heat and pressure. Also helping the motor to cope is an improved oil supply system with modified sump and higher capacity oil pump.

The SL55's engine bore remains the same as the SL500's, but stroke for the AMG was increased from 84.0mm to 92.0mm, giving the 5.4-litre capacity that is 473cc greater than the SL500's. Other changes made by AMG include cylinder heads with revised intake and exhaust ducts, higher-lift camshafts with longer opening durations and double springs for the valves.

Mercedes also used the SL55 to introduce fully computer-controlled engine mapping for the first time on its road cars. Along with the SL55's twin catalytic convertors; it managed carbon dioxide emissions of 340g/km, which were considered very reasonable in 2002.

Problems with the M113 V8 are very rare as it's a strong engine. Check the oil and coolant fluids are clean to the level, and make sure all of the visible pipework is in good condition as access around the engine is tight. The charge cooler for the supercharger sits in the engine's V and uses its own radiator, so have this checked for leaks or corrosion. A squeaky supercharger can be made quieter by squirting some graphite spray down the head of the supercharger. It's not a complete fix, but the supercharger is a strong unit and should give no problems, even with an uprated pulley fitted from established tuners such as Kleemann.

Much more of a worry is the five-speed automatic gearbox, which also came with paddle shifts mounted on the rear side of the steering wheel. On any test drive, check the gear lever slots from Park into Reverse, Neutral and Drive cleanly. If there's any hesitation, resistance or it needs to be given a shake to make it work, the plastic peg that prevents the lever inadvertently being knocked into Reverse without the driver's foot on the brake is about to break. It's a relatively easy part to replace and there are direct replacements made from aluminum available that cure the fault. A Mercedes dealer may elect to replace the entire unit. The gearbox also needs its fluid completely changed every five years, so early SL55s will need this addressed right about now.

The rest of the SL55's transmission is very tough, though watch out for cars that have been used on track as the AMG's weight will give every component a hard time. In normal mixed driving, the SL55 should go 12,000 miles between services.

Rolling chassis
Mercedes fitted its ABC (Active Body Control) as standard to the SL55 AMG, which allows the car to corner more flatly yet retain a comfortable ride. It uses hydraulically controlled servos connected to the springs and dampers and did away with the need for anti-roll bars. This didn't stop AMG's engineers coming up with improved, stronger rear axle mounts, a beefier steel sub frame and better spring links.

Undoubtedly a clever solution, ABC now poses a worry for potential SL55 buyers as the pipework corrodes and lets fluid leak away. In turn, this lets the ABC's hydraulic pump run dry, which is usually the first component to be blamed for the system failing. Check the pipes carefully and budget for replacement if there are any signs of corrosion. In doing so, you may save yourself the cost of a new ABC pump, so check for any signs of fluid leaking underneath the car.

Another leak to watch out for is from the fuel tank caused by a faulty fuel pump. Again, most will have been replaced under warranty by Mercedes, but some cars were missed and are spotted by a ticking noise from the tank when it's less than three-quarters full.

The SL55 was blessed with improved brakes over the standard SL range, gaining eight-piston calipers biting into 360mm vented discs at the front. This set-up almost doubles the front pad face to 220 square centimetres compared to the SL500. At the back, there are 330mm vented discs and early SL55s came as standard with multi-spoke 18-inch AMG alloy wheels. Later cars were fitted with 19-inch twin-spoke alloys that are easier to clean and less prone to kerbing.

You can expect the brake pads to last around 20,000 miles in normal driving, but they do wear more quickly than most cars'. Discs will also need replacing more frequently than with many other cars of similar performance, but the ESP and Emergency Brake Assist systems are reliable and hassle-free.

However, the Sensotronic Brake Control (SBC) was subject to two recalls early in the SL55's life. One was for a software update to the ECU and the other was to check for problems with the brake's hydraulic system. A check of any SL55's history file should tell if this work has been required and carried out, so don't buy any SL55 without a complete history record.

Finally, tire wear should not be any worse than for a comparably quick and powerful rear-wheel-drive car. The front tires are 255/40 R18 and 285/35 R18 at the rear for earlier cars.

Body
While the brand new SL launched in 2012 has a monocoque made from 90 per cent aluminum, the SL55 that is part of the R230 generation has a steel monocoque. However, Mercedes made extensive use of aluminum for many of the body panels to help keep weight down. This means a thorough check of the body for dents and parking dings is essential as aluminum is trickier and pricier to fix.

The SL55 uses the folding metal Vario-Roof that incorporates aluminum to help reduce weight. While the roof itself is no cause for concern, the seal between rear windows and body is, which leads on to problems with the roof's electric motor, the central locking and alarm. When these seals fail, it allows water into the boot where it gathers around the roof's motor. To make matters worse, Mercedes surrounded the motor with foam to insulate the cabin from noise when the roof was being operated. The foam acts as a sponge, holding water around the motor and causing it to fail.

When looking at any SL55, or any SL of this era, lift the boot carpet and feel for damp. Any signs of water are bad news and likely mean you'll need to replace the electric motor. This is the root of all the stories about the SL's folding roof failing, even though Mercedes tried to rectify the problem when the car was new. Some cars still suffer from this fault, so inspect any SL55 carefully.

Mercedes finally cured the leaky roof issue in 2005 with redesigned seals and these may well have been retro-fitted to an earlier car you're considering. While checking the roof, also listen out for any rattles when the roof is raised. It's not uncommon for the roof to creak a little, but it can be the sign of poor alignment from the factory or, worse still, crash damage.

Distinguishing features for the SL55 from the outside are the 'Kompressor' badges on either front wing, a deeper front splitter, side skirts and dual twin tail pipes for the exhaust. All body panels are readily available for any crash repairs.

Interior

Mercedes didn't stint on luxury when it came to the SL55's cabin. Unique perforated AMG leather covers the sports seats with extra bolsters for added support, while Alcantara is used on the instrument binnacle and front edge of the gear lever. There's aluminum trim for the center console and door trims, and it's also used for the door sill plates with AMG logos.

The SL55 was offered with three interior options for the leather. They covered black and graphite, alpaca dark grey and alpaca grey, and black and berry. For the instruments, AMG's unique script is used for the numbers on the main dials, which have silver faces and red needles, and there are 'AMG' and 'V8 Kompressor' logos on the lower part of the dials to remind the driver of what's under the bonnet.

From launch, the SL55 came as standard with Mercedes' Audio 30 stereo system, twin front and side airbags, electric windows and climate control. All of these have proved to be trouble-free and the electrically adjusted leather seats are hard wearing. However, it's worth tipping the seat backs fully forward to check the well at the rear of the seats for damp. This is another area where water collects if the rear windows seals are faulty. Also be sure the central locking and alarm function properly as their controls are in the boot next to the roof's motor that is susceptible to water ingress from leaky window seals.

Most of the electronics in the SL55 are reliable, but press every button to be sure. The optional Command satellite navigation may seem outdated now, but it's worth checking it works. The Linguatronic voice recognition system was never the best at understanding voices and accents and its worse when the roof is lowered at higher speeds.

Some of the warning beeps in the SL55 can ping on, but several are over-sensitive, such as the alarm to tell you the bonnet and boot are open. A good specialist with resolve these issues and plenty of owners tell us Mercedes dealers have improved their customer service considerably from the early days of the SL55.

Source: http://www.pistonheads.com/doc.asp?c=52&i=25445
 by Alisdair Suttie

 

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