Buyer’s guide: Mercedes-Benz SL (R129)

By Malcolm McKay

| 1 Mar 2019

Classic & Sports Car – Buyer’s guide: Mercedes-Benz SL (R129)

Why you’d want a Mercedes-Benz SL (R129)

Mercedes brought the SL bang up to date in 1989, with sharp Bruno Sacco styling and a technology overload.

Built over 12 years with straight-six, V6, V8 and V12 engine options ranging from 2.8 to 7.3 litres, the R129 came in many forms, all of which have their fans.

The car was based on a shortened W124 platform, which provided multi-link rear suspension and optional electronic adaptive damping. A built-in, automatically-raised rollover bar was a distinctive safety feature.

The smart hardtop was heavy – a two-man job to remove, especially in later Panoramic (glass-top) form – difficult to store and easily scratched, but it looked great: make sure it’s still with the car. Rear-seat space is limited; front-seat occupants will have to sacrifice legroom to squeeze adults in the back.

AMGs such as this SL60 are rare, and desirable

During production, Mercedes changed from the 24-valve, twin-cam M104 straight-six and 32-valve quad-cam M119 V8 to the 18-valve single-cam-per-bank V6 and 24-valve quad-cam M113 in ’98.

Some power outputs were marginally down, making the 1995-’98 five-speed auto SL500s the most sought-after of the standard cars.

The ultimate cruiser is the 6-litre V12 600 with 389bhp, while the top sporting models are the AMGs: all are rare, but you may find a bored-out 6-litre V8 AMG SL60. AMG chose the V8 because it was lighter and could be made to handle better. The V12 600SL was more tuned to US motoring, though a sports-car character shone through when it was pushed hard.

Unusually, though corrosion is not a big problem on these SLs, later cars are more prone; there are dark mutterings that, after merging with Chrysler, Mercedes was cutting costs…

All are laden with electric and electronic trickery, increasingly so on later and higher-spec models. It’s all wonderful when it works, but inevitably age and damp wreak havoc with rarely-used contacts – and when those are inside sealed units, rectification gets costly; 1993-’95 cars also suffer from degradation of the wiring harness in the engine bay.

Try to find a car with a sheaf of bills for keeping the details working, as well as regular servicing: there’s a big variation in prices between cars with dubious vs impeccable history, because of the huge potential cost of bringing a neglected car up to standard.

If you fancy an AMG, be prepared to pay double or more than the price of an equivalent SL500.

Mercedes-Benz SL (R129): what to look for

Bodywork

See above for trouble spots

Engine

Full service history is vital. The V8 engines will go on for ever if serviced, but listen out for rattly cams and lifters. V12 and 300-24 head gaskets can fail (c£1500 to replace on the ‘six’, much more on a V12), and it’s wise to replace the water pump on straight-sixes if it hasn’t been done. Check for oil leaks, especially on V12 units

Transmission

Look for smooth automatic gearchanges, without delays, slipping or jerkiness, and check the fluid is clean and not burnt. Manual ’boxes shouldn’t be notchy or vague.

Hood

Check hood operation is smooth and for header-rail hydraulic leaks; plastic windows can be replaced (c£1000). Watch for fading soft-top deck covers.

Interior

A neglected interior indicates a neglected car, though Nappa leather wears quickly. Check all electrics work, and for cracked sunvisors or a faded heater panel display.

Automatic roll-over protection can also be raised on a button. Test all electrics because there’s a lot that can go wrong: seats, headrests, hardtop release.

Wheels

Look for wheels’ spec and corrosion, tyre age and quality, and worn/seized brakes: there were multiple spec variations in brake size and calipers.

Air-con

A failed condenser is the most common cause of ineffective air-con. It’s vital that correct coolant has been used; ‘sixes’ run hot when fan couplings fail.

Mercedes-Benz SL (R129): on the road

R129s are hugely complex

All R129s should feel lively and under-stressed on the road, especially V8s and V12s. The sturdy V8s are the most dependable, usually suffering only minor ailments. An M119 sounding tappety is likely to need new plastic cam oilers (c£600 to replace all 16), while poor hot starting on later M113s is usually a crank sensor: an easy fix.

Check that the ’box shifts smoothly into all gears (including reverse); the five-speed auto on ‘sixes’ can have issues getting fifth. Confirm that the oil and filter have been changed at least every 40,000 miles; for a while they were ‘sealed for life’ until Mercedes realised that was a mistake…

The suspension and steering should operate quietly and comfortably, with no knocks or sloppiness. It’s a heavy car, so dampers, bushes, suspension top mounts and steering box – and especially the idler – do wear, and springs break.

They’re hugely complex: the first cars had a remote-control rear-view mirror and auto-locking door pockets, dropped in 1995. All had an auto-locking centre console and boot storage compartments, and ’97-on cars have three-way programmable garage door transmitters on the rear-view mirror, plus rain-sensing wipers.

A separate electric water pump feeds the heater (and fails). ADS active damping was optional: it’s great, but needs an expert to sort it if faulty.

Every aspect of the seats adjusts electrically (check heat pads, too), and hardtops are released and lifted electrically – impressive if it works! A weak battery can cause stray warning lights.

Mercedes-Benz SL (R129) price guide

300 / 280

Show: £15,000
Average: £5000
Restoration: £2000

320+500SL

Show: £20,000
Average: £7000
Restoration: £2500

SL500

Show: £27,000
Average: £11,000
Restoration: £4000

V12

Show: £30,000
Average: £12,000
Restoration: £5000

Mercedes-Benz SL (R129) history

1989 R129 launched as the 300SL (188bhp), 300SL-24 (228bhp) and 500SL (326bhp)

1990 Catalysed 500 down to 308bhp

1991 AMG 500SL 6.0 launched

1992 600SL V12 added, 0-60mph in 6 secs

1993 Model names reversed; 300s replaced by twin-cam, straight-six SL280 (193bhp) & SL320 (228bhp); 381bhp SL60 AMG, 0-60 in 5.6 secs

1994 Electronic odometer introduced

1995 Facelift: 2-slot wing vents replace 3-slot, body-colour bumpers, side airbags, V8/12 get 5-speed electronic auto; 518bhp SL72 AMG

1996 Optional Sport package (18in wheels and trim changes), and Panoramic hardtop; Mille Miglia special edition and 489bhp SL70 AMG

1997 40th Anniversary Roadster & SL73 AMG

1998 Facelift: Nappa replaces perforated seat leather, oil temp replaces pressure, computer, one-touch starting, body-colour doorhandles, new rear lights, V8s now sohc M113, 280/320 now sohc V6 (201/215bhp); 349bhp SL55 AMG

1999 Silver Arrow special edition

2000 Alanite Designo special edition

2001 Production ends, 213,089 built

The owner’s view

Brian Kelly has a 1999 SL500, later than the car pictured: “I bought a CLK320 in 2001 and enjoyed that, but then I made the mistake of trying a V8! The 3.2 is spirited to drive: the V8 does the same but feels so much more relaxed.

“I looked for an M119, but there weren’t many to choose from. I bought this one at the bottom of the market, 61/2 years ago: it had an electrical issue where you’d switch one item on and it would cut another, plus it needed a plug change; it had 11 past owners but had a good service history and I got it for £6500. It’s Tanzanite Blue with Panoramic roof and Albali wheels – it’s totally original and was a really good buy.

“From the R129 forum, I learned that the electrical problem was a burnt contact on the ignition switch – easily sorted. I service it myself: it’s a hands-on car. I had to change a headlamp wiper motor and got the parts from eBay. I was going to trade it in for an SL55, but I didn’t feel at home in one, so I’ve decided to keep it.”

Also consider

Jaguar XJS (left) and Cadillac Allanté are alternatives

JAGUAR XJS

Great parts supply makes the XJS a tempting alternative, but there’s still a lot to go wrong and they are prone to rust, too. Buy on condition and history.

Sold 1975-’96 • no built 115,413 • price now £8-30,000 (convertible only)

CADILLAC ALLANTE

Oddball front-drive V8 answer to the SL was Pininfarina-bodied: shells were flown to Detroit for finishing. In LHD only, and just a handful of cars came to Europe.

Sold 1986-’93 • no built 21,430 • price now £5-15,000

Mercedes-Benz SL (R129): the Classic & Sports Car verdict

Lots can go wrong with the R129, so buy wisely

Asking prices vary widely and often illogically, so check very carefully which model you want, drive a few and focus relentlessly on condition, specification and – above all – full, caring history. Or buy a cheap but clean one and keep thousands in your back pocket for when it goes wrong: it will.

Low mileage is not always good, especially if recent use has been minimal.

FOR

Superbly built
Attractive
Practical, with effortless performance

AGAINST

Biased more towards comfort than sporting handling
Extremely complex, so there’s lots to go wrong
Many have now suffered years of limited maintenance

Mercedes-Benz SL (R129) specifications

Construction steel monocoque

Engine iron/alloy sohc 2960cc or dohc 2799/2960/3199cc ‘six’; all-alloy dohc 4973cc V8 or 5987cc V12, or sohc 2799/3199cc V6 or 4966cc V8; Bosch electronic fuel injection; 188bhp @ 5500rpm-389bhp @ 5200rpm; 191lb ft @ 4400rpm-420lb ft @ 3800rpm

Transmission 4/5-speed auto or 5-speed manual, RWD Suspension: front MacPherson struts rear multi-link; optional Active Damping System; coils, telescopics, anti-roll bar f/r

Steering power-assisted recirculating ball

Brakes ventilated discs, with servo and ABS (early 6-cyl & 280 non-vented rear)

Length 14ft 8in-14ft 10in (4470-4521mm)

Width 5ft 11in (1811mm)

Height 4ft 3in (1295mm)

Wheelbase 8ft 3in (2515mm)

Weight 3630-4356lb (1650-1980kg)

0-60mph 5.9-9.5 secs

Top speed 140-159mph

Mpg 15-25

Price new £49,960 (300SL, 1991)

BUY A CLASSIC MERCEDES-BENZ SL (R129)