Mercedes R129 SL Buyer's guide


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When the R129 SL was introduced in 1989 it heralded a new era for Mercedes. Gone were the ageing looks of its predecessor and the manufacturer’s reputation for dependability above style. The R129 bridged the gap between the bullet-proof Mercs of yore and the stylish (and fragile) Mercs of the Noughties. It is a sweet spot in the Mercedes back catalogue and an affordable classic.

  • Models produced: 213,089
  • Models remaining: 4,000 (UK 300 SL, approx)
  • MOT pass rate: 77.8%
  • Engine: 3.0 L 12-valve SOHC I6 (300 SL)
  • Power: 188hp (300 SL)
  • Torque: 192 lb⋅ft
  • Top Speed: 142 mph
  • 0-60 mph: 9.3 secs
  • Fuel Consumption: 15-25 mpg
  • Gear box: 5-speed 5G-TRONIC
  • Weight: 1650-1980kg (3630-4356lb)
  • Wheel base: 2515mm (8ft 3in)
  • Length: 4470-4521mm (14ft 8in-4ft 10in)
  • Width: 1811mm (5ft 11in)
  • Height: 1295mm (4ft 3in)

About the Mercedes R129 SL

The R129 is celebrated for its styling. It was designed by Bruno Sacco in 1984, incorporating stringent crash regulations and boxy Eighties styling better than many of its rivals. As a result, the R129 was bought in droves for more than a decade. It still looks fresh today and could teach contemporary Mercedes designers a thing or two about design. However the R129 championed engineering and technology too. When it launched in 1989 the SL was - Mercedes claimed - the safest car in the world. Look deeper and it's easy to see why. The R129 had automatic roll over hoops that deployed within 0.3 seconds if the car sensed it was about to flip over. Another feature was the integrated seatbelt, which was attached to the seat rather than the b-pillar, isolating occupants from violent impacts absorbed through the body. Lots of options and switchgear were carried over from the S-Class and the SL became what it is today - a two-seater tech barge. It was also the last Mercedes to be overengineered, before the dodgy build-quality of early Noughties cars tarnished Merc’s reputation. The SL was face lifted in 1995, nipping and tucking the styling (including reshaped bumpers) and offering a panoramic glass hardtop as an option.

Bodywork

Although the SL dodged the rust issues that many Mercedes of this era suffered from, check for corrosion in the wheel arches, especially at the front where the arches join the bumper. While you’re down there inspect the inner wings and behind the side slats. Check for corrosion on the hardtop, particularly at the base of the B-posts and ensure the soft top is in good condition and operates smoothly. It should be in usable condition because having the hard-top saves it from harsh winter conditions. Don’t fret if the plastic rear window is cracked because it can be replaced and restitched by a trimmer without replacing the whole roof. Check for any rust on the boot floor, especially near the battery.

Engine

The SL is tough and well-engineered, but they aren’t infallible. Early cars with the 2.8-litre and 3.2-litre straight-six engines are prone to wiring loom degradation and oil leakage from the head gasket. The crankshaft damper pulley can also fail on the early 320 which damages the timing case cover. It’s a good idea to replace the water pump on straight-sixes if it hasn’t already been done. The V6s and V8s are very reliable, with no major problems to watch out for. The V8s are particularly hard wearing if properly maintained. Full service history is a must. Listen for any sign of rattly cams and lifters. Check for oil leaks, especially on V12 cars. Maintenance is paramount with the SL, as failures or replacement parts can be costly.

Gearbox

The SL’s auto boxes were never the fastest things in the world but gear changes should be smooth and without delays. Ensure the fluid is clean and not burnt. The manual shouldn’t be notchy.

Suspension

The front strut top mounts wear on all cars, especially on V8 models thanks to the additional weight at the front. You may not realise this from behind the wheel so look under the bonnet for rubber top casing cracks.

Electrics

The SL is massively complex. It was Mercedes’ flagship roadster and engineers threw every bit of cutting edge Eighties technology at it, with mixed results. The R129 can suffer badly with battery drain. If the car isn’t used regularly buy a trickle charger. Avoid jump starting the car using a booster pack, as this can spike control modules including the roof control. The early cars suffer more electrical issues than the later facelifted models. Common problems include ABS, wiper relays and roof control modules. Have a fiddle with the electrics when you view a car because there’s a lot that can go wrong with the SL. This is a car that prides itself on its gadgetry, and twenty years of decay is a recipe for massive bills. Inspect the seat and headrest controls, as well as the hardtop release.

Interior

The SL’s interior is famously hard wearing. This was designed and built in an era of incredible Mercedes reliability and everything in the cabin is over-engineered. The interior should feel tight and solid if it’s been properly maintained. If it doesn’t then you should walk away. Make sure the air conditioning works because chasing faults in the system can get pricey. Wear to the side bolsters of the seats, especially on the driver’s side, is common so don’t worry too much. It can always be replaced or corrected without breaking the bank.

What’s it like to drive?

The SL is a luxury cruiser and should waft along serenely. It might look like a sports car but treat the SL like a two-seater S-Class. This is a car for gentleman drivers, not boy racers. R129 engines should feel torquey and under-stressed, especially V8s and V12s. The steering was never particularly responsive but it should feel smooth and free of corruption. The same goes for the suspension. It is damped for relaxed driving, but remember this is a heavy barge so there’s a lot of strain going through the dampers, bushes, top mounts and steering rack. This can cause wear and even breakages over time, so listen out for any unusual squeaks and groans from the suspension.

Price Guide

SL prices are wide-ranging and often illogical. This is partly due to the exhaustive list of options and trim levels, as well as the amount of engine choices. There is also the matter of age. The R129 is not yet old enough to be considered an out and out classic, and thanks to the huge production numbers and reliability it's not rare either. Use this to your advantage. Try out as many SL’s as you can, with different engines and options until you find the specification that best suits your needs. Prices for the basic 300 model average around £5,000, with project cars starting as low as £2,000. Beware of steep parts costs and servicing bills with bargain basement SLs. You can pick up a decent SL500 for around £12,000, and a V12 for a couple of grand more if you’re willing to buy a well-worn example.

Running costs

You will be forgiven for thinking that the R129 is a bargain, and in some ways it is. But while a scroll through the SL classifieds can leave you excited, it can prove too good to be true. The R129 was a complex machine from an era of dodgy electrics and unproven gadgetry. If you pick up a cheap example with less than perfect service history you are guaranteed big bills. There is an endless list of electrical gremlins that can crop up and cost you thousands, and Mercedes parts and labour costs never come cheap. Make sure you pick up a car that has been fastidiously maintained and serviced regularly. Like any classic car, these examples demand a premium but it will save you thousands in the long run.

The Verdict

The R129 was arguably the best Mercedes roadster since the Pagoda, and Bruno Sacco’s design has aged beautifully. It has a dignity about it that Mercedes has failed to recreate and represents a fantastic opportunity to waft to the golf club on a budget. As long as you watch out for electrical gremlins and patchy servicing, you can enjoy countless miles in one of the best Mercedes sports cars ever made.

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