If you’re looking for a convertible with four seats, a good level of refinement, as well as a touch of class, then there are few better steers than a Mercedes SL. Want one that is relatively affordable, as well as cheap to run, then it’s almost impossible not to find yourself browsing the classifieds for an R129 SL – an SL for the 1990s.
As with the previous SL roadsters, the R129 shared a basic platform with the mid-range saloon contemporary – in this case, the W124 series. Featuring an advanced five-link independent rear suspension, recirculating ball steering and strut suspension up front, the SL excels as a grand tourer, with relaxing, stable handling. Along with this, the R129 SL offers perhaps the best seats ever designed (with electric adjustment including the seatbelt) and enough cabin space to carry a significant amount of luggage.
Seen as a large car at launch, it fits into modern traffic surprisingly well, and is easy to place on the road. The flat rear deck and square cut boot, combined with either the large rear window of the soft top or the standard equipment hardtop make for rearward visibility that is the envy of most modern hatchbacks, let alone convertibles – and yes, the rear view mirror is electrically adjustable.
Which one to buy?
The SL launched in 1989 with three engine options. Two 3.0-litre straight sixes – the M103 and M104 with 190bhp 12v and 231bhp 24v respectively, and the robust 32v M119 5.0-litre V8. The 300SL and 300SL-24 were available with a choice of manual or automatic transmissions, the 500SL shipped with an old-tech four-speed automatic only. In 1992, the V12 600SL joined the range with the M120 48v near-400bhp engine, reinforcing the SL’s move upmarket.
The M119 32V 500SL is responsive, with a 6 second 0-60 and a top speed limited to 155mph, yet will return around 30mpg at motorway speeds. The old-school automatic gearbox impacts urban economy.
Straight-six models are, by comparison to the 500SL, adequate. The manual box shares a ponderous, detached shift feel with the Mercedes saloons the car is derived from, and the 300SL engines are surprisingly subdued, getting on with the job quietly. Economy is not significantly better, but you will be beaten to 60 by some very mundane vehicles indeed, particularly with the auto.
The greatest sacrifice in the straight-sixes is losing the sound of the M119 V8 at high RPM. The 500SL might be a relatively tame beast, yet it carries the heart of a Le Mans winner; the Sauber C9’s fortunes having been reversed with the update from an M117-based engine to the M119.
Mercedes-Benz’s over-engineered approach extended to accepting the limitations of the folding roof. It is not a substantial, heavily lined item, and the design does include some inherent security weaknesses that are indicative of the occasional use intended for it.
The vacuum locking system therefore extends to the rear seat cubby boxes, the door pockets, the centre console - anywhere you might want to hide things is locked with the doors. For models without rear seats, the platform behind is large enough for a couple of typical weekend bags, the boot is large and includes space for storing a wind blocker.
Initially launched with a four-speed automatic in the V8/V12 models, an option of 5-speed automatic in six-cylinder versions, and Mercedes’ agricultural manual five-speed box as an option on six-cylinder models only, in 1996 the range was updated to receive the electronically controlled 5G-Tronic automatics.
A number of special editions were produced, most notably the Silver Arrow and Mille Miglia. The latter was produced in 1995 to honour Stirling Moss’ 1955 win, in 320 or 500 form with a limited run of 50, before a number of reruns - and featured silver paint, red and black interior with carbon fibre trim, six-spoke “Evo II” alloys and chequered flag decals behind the wing vents. The Silver Arrow was a run-out model, named in honour of the 1930 racer and featuring extra bling (Illuminated door sill trim, bright window surrounds).
Of note, V8 and V12 AMG models also graced the R129 range. The V8 SL60, which uses a 6-litre, 381bhp version of the M119 V8 and was produced between 1993 and 1998, the very rare 1997 SL70 with 7-litre 496bhp V12 and the 525bhp SL73, which uses the same basic 7.3 litre engine as the Pagani Zonda and other AMG V12-based supercars. Finally between 1998 and 2002, the SL55 AMG was offered, with 5.4-litre M113 serving up 354bhp; a precursor to the R230 SL55 and indeed, to the greater volume AMG would enjoy in the 21st Century. SL60s come up relatively frequently, albeit with a substantial premium.
Other tuners, notably Brabus and Renntech, also offered tweaked R129s – these should be bought very much on their own merits and provenance.
Performance and specs
1989 Mercedes-Benz 300SL-24
Engine 2962cc in-line six-cylinder
Power 231bhp @ 6300rpm
Torque 201lb ft @ 4600rpm
Top speed 137mph
Fuel consumption 21.4mpg
Gearbox Four-speed automatic/five-speed manual
Dimensions and weight
Kerb weight 1692kg
• Oil pressure should read '3' most of the time but a drop to 1.5-2 when hot at idle is normal. If it’s low when driving on a car with under 150-200,000 miles, walk away. If the gauge is non-functional it may be a cluster or sensor, which is mounted in the oil filter mounting.
• Engine management and injection systems evolved, with the earliest cars using a mechanical fuel injection (K/KE-Jetronic), changing to sequential LH Jetronic in October 1992 then Motronic. Ignition on earlier cars uses two coils and two distributors, one set per bank; service items are cheap but you need two of them, a tolerable compromise. The spark controller ECU can be expensive if it has failed.
• Oil starvation can cause problems with the camshafts, initially due to hydraulic lifters failing to pressurise - kits to replace the seals are available and easy to fit. The plastic components go brittle with age and break down; on a car with more than 150,000 miles look for this work to have been done.
• The M103/M104 engines in the earlier (pre facelift) SLs are similarly robust, needing merely consumables and maintenance to keep running for 300,000-400,000 miles.
• Post ’93, problems can be found with wiring harnesses on all models of SL. Insulation breaks down inside the loom, with many unrelated issues making diagnosis fun – the engine wiring harness for an SL 500 is £714 from a main dealer.
• The V12 M120 engine not only suffers the same problems with wiring, the cost of consumables and densely-packed engine bay make regular maintenance less pleasant than the V8.
• The manual transmission is reliable, but the simple, tough four-speed boxes are a better ownership proposition when buying at the budget end of the market. The 722.3 600SL gearbox was sufficiently strong that Brabus used it in their 7.3-litre V12 models unmodified!
• The later five-speed 5G-Tronic 722.6 was initially treated as a sealed for life unit, and was fitted with a tamper-proof cap. A red tab indicates it has been serviced, a black tab that it has either never been checked, or has only been touched by approved Mercedes service centres. Mercedes-Benz has subsequently revised and recommended fluid changes every 40,000 miles.
• There are economy and performance benefits to be had by opting for the later gearbox, but it’s necessary to be aware of leaks into the wiring loom from the electrical connector. Look under the car at the multiplug, signs of dampness and residue are a useful early warning. Also look for history with evidence of correct fluid and filter changes. The loom issues can cause the car to shut down whilst driving, and are an involved repair.
• Drive with the roof down, and listen for noises from the rear drivetrain. Shifts on the four-speed are slurred, but swift - if delayed changes (without kickdown) or jerky downshifts in particular are present, check the oil level and for the usual burnt, brown fluid indicative of poor maintenance. The five-speed automatic will hold the lower gears until the car is warmed up, and shifting can be more obvious under power, though any hint of slipping should be a warning.
• With the manual, look for vague, notchy gearchanges. If it has them, it’s working fine. Should there be issues with the clutch, release bearing or props, most are easily sorted as the car is no more complex than a W124 300E.
• As the R129’s values have decreased, the popularity of aftermarket rims and fake AMG rims has increased. What you are looking for are genuine Mercedes part numbers, so if in doubt, remove the wheel and look at the back. Tyres should be an appropriate brand and rating for a 4500lb car that can comfortably achieve 150mph, skimping on these implies skimping elsewhere.
• The steering is precise, but detached, a variable-rate power assisted system with recirculating ball. A worn steering damper is frequently overlooked, inexpensive and can cause vague response, vibration and wandering.
• True gluttons for punishment can opt for Mercedes’ Active Dampening System. This option, standard from 1993 on SL600s, provided a Citroen-esque hydraulic suspension with height control, active correction when cornering and load leveling. Controlled by yet more of those ‘90s-era ECUs, the recipe for high repair bills is spiced up with the application of nitrogen spheres and a lack of specialists and experience in the UK, particularly as the cars have dropped out of the main dealer network.
• Spheres are inexpensive and should be replaced every five-six years, but most problems occur with the valve blocks and sensors. For the determined and competent DIY repairer, it should be simple to maintain; for those who just want to pay for the car and enjoy it, vital components of the ADS system are four-figure modules. Naturally for UK owners you can add the delights of salt-assisted corrosion to any attempt at maintenance.
• Later models involve more electronic intervention – and electrical gremlins can crop up throughout the ABS, ESP, ASR and where fitted, ADS systems, regardless of generation. As an entire guide could be written just on the R129’s subsystems, it’s sufficient to say that if any warning lights are on, or anything behaves in an unpredictable manner, it will not be cheap to have fixed by a dealer. On the upside, many of the simpler components are inexpensive, and Mercedes continue to stock spares for older models.
• Brakes are powerful, responsive and should have good feedback. Warped discs are a risk for any heavy automatic car, and vibration under braking can also show the early stages of wear in the lower balljoints. Mercedes discs are £61-91 each (rear/front) with a set of pads costing £55. Incorrect brake bleeding can cause issues with the ASR traction control, including reduced power, and result in costly diagnosis.
• The R129 can of course rust, especially where accident damage has been repaired, so check everywhere, particularly in the boot panels near the battery box. Weak points of the R129 regardless of history are the leading edges of the front wings, and crucially, the jacking points.
• The car’s sills and tubular jacking points are covered with plastic protectors, which combined with damage to the paint finish inevitable if the factory jack has been used can quietly rust away for years without the owner being aware. Pop the jack covers off and check.
• Body fit and finish should be perfect. The trim and folding panels for the convertible top should sit flush, and the car should have a hard-top – every SL came with one. A desirable non-standard option was the hardtop stand, preventing damage to the header rail, mounting tabs and rear trim when removed.
• If the car has the hard top fitted when viewed, ask to remove it. Problems with the complex electro-hydraulic roof system on the R129 are expensive to resolve, with 11-12 hydraulic units, many switches and feedback loops involved for each stage.
• You also want to inspect the condition of the fabric roof. The cabriolet roof should close and open quite quickly. Unlatching the hard top will only work with the ignition on; if the engine running the function is only activated for the first few minutes, then disabled to prevent accidental release.
• Check operation of the roll bar – one, you want it to work if you crash, and two, if it is stuck in the raised position, the roof won’t work.
• Finally, if the car’s roof is not working, it is as always a case for haggling if you’re looking to buy at the budget end of the market. A cheap R129’s roof is either broken or not broken yet. Budget around £1800 for specialist repairs if you’re not confident taking it on yourself – not including repairs to the roof or rear window material.
• The electrical system of the SL is complex, and faults are frequently exacerbated by the attentions of auto electricians installing third-party accessories. The demographic and era placed the R129 into the heart of telephone and alarm fitting.
• Adjustment of the steering column, all three mirrors, seats and seatbelt is electric with memory, heating and ventilation is wholly electronic in control, and a rare trip computer is available with display concealed in the compartment above the heater outlets. 1993 models onwards have an electronic odometer.
March 1989: The all-new Mercedes R129 was unveiled at the Geneva motor show.
1993: 12-cylinder SL600 model introduced
1995: The interior was redesigned with rounded door trims, side airbags, ESP and the panoramic hardtop option was introduced.
1998: To coincide with the engine range changes, the mirrors, body cladding and bumpers were changed again, with a softer look.
July 2001: The R129 is replaced by the new R230 SL
Owners clubs, forums and websites
Summary and prices
The R129 may have been a culture shock when first launched, yet it has aged nicely and still looks cohesive, even elegant compared to the fussy and contrived lines of its R230 successor. With many cars costing upwards of £70,000 new – some AMG variants could double that – the realistic price band of £5000 to around £20,000 encompasses reliable daily runners and the lower end of the AMG market.
Below £5000, good usable six-cylinder models and slightly rough V8s lurk, though if a 600SL were in that price bracket it would be a brave buyer indeed taking it on. For a competent enthusiast, the engineering behind the SL ensures that it can be a time consuming but satisfying car to own, and surprisingly inexpensive to run, regardless of year.
For those who just want to drive and enjoy the cars, between £3500-5000 the straight-six 300SL between 1990-1993 is the safest option. If only a V8 will do, pre-’92 500SLs are the easiest way to avoid inherent flaws in the wiring. Increase the budget to £6500-8000 and it should be possible to get a late 32V SL500 with 5G-Tronic, with SL600s starting at £12,000 for examples with good history. AMG SL60s can be found surprisingly frequently for around £15,000-20,000.
With all models of SL, dealers will throw just about any price into the air. It’s entirely justifiable to pay a premium for an example with history and in exceptional condition, but one thing the R129 SL doesn’t respond well to is neglect – they will carry quarter of a million miles with the grace of 50,000, and often react to being thrown into service after a period of rest by failing in an astounding variety of ways.
The best buy? 1997 SL500 with Panoramic Top, standard suspension, average miles and a thorough history showing attention to common failures. The worst? As a money pit, the 1994 SL600 with low mileage and only dealer stamps has a lot of potential. However, the R129 shines with lots of power, so the SL280 with 9.5 second 0-60 is the one that misses the point. Even then, if the price is right and you just want to cruise...