Mercedes-Benz SL R107 Buying Guide

BUYER’S CHECKS

Buying a good R107 SL can be a very rewarding experience. Buying a bad one can leave a hole in your bank account and take the shine off owning one of the best cars to come from Stuttgart.

R107s are very resilient to high mileage, and although low mile cars command a premium they are not always better cars to drive or own.

Judge each car as you find it, not by the miles on the odometer or the asking price.

A complete service history is vital if you are buying privately, or without a warranty or comeback, as these cars are able to do huge mileages and hide neglect. In our opinion, neglected cars will bite back and probably end up costing more than the right car you should have bought in the first place.

Ideally, your R107 SL should be as it left the factory, with the right road wheels and correct interior, carpets, hood etc. Avoid those cars with aftermarket wheels and nasty bodykits.Drive as many cars as you can, as they all feel slightly different.  You’ll only notice a tired one when you truly have the feel of them.

Rust is a major factor with 107s, so check the body thoroughly –  above the headlamps, bonnet, bootlid, rear arches, bottoms of the doors, sills, lower half of the body and floors. Check them all before you hand over your hard earned money for that car on eBay that looks great value for money! We rectify numerous cars bought in haste that have been inaccurately described.

COMMON ISSUES

– Vague Steering

Symptoms

Vague or wandering steering, and play in the steering box.

Diagnosis

Every R107 SL is prone to lose, vague or sloppy feeling steering, robbing you of driver satisfaction and making for frustrating motorway cruising. There are two main causes of this problem…

The steering box: The SL’s steering box is designed to be adjustable to a point. With use and adjustments over time, the steering box may develop extensive movement resulting in the car’s steering feeling vague and loose. 

The steering damper: This piece of apparatus is like a horizontal shock absorber for the steering. With age, the steering damper will become worn and less efficient, resulting in the loss of the SL’s factory fresh feel.

The Cure

More often than not, an adjustment to the steering box is all that’s required to fix your SL’s steering issues. If the steering box has had all of the adjustment it can take, then we can send it away to a specialist for refurbishment. This service costs roughly half that of a new, genuine Mercedes-Benz steering box.

– Tyres

Symptoms

Poor handling in wet conditions, bald tyres and cracked sidewalls.

Vehicle affected

R107 SLs with either 14-inch or 15-inch wheels.

Diagnosis
Tyres are a regular service part that will wear out over time and with use. Buying budget tyres will result in quicker wear and tear, but even a tyre that has plenty of tread on it will become unsafe as the rubber degrades over time.

The Cure
SLSHOP is able to supply and fit a wide range of tyres for your classic Mercedes-Benz. Your choice of tyre will on depend on budget, personal usage and past experience. SLSHOP is able to supply premium brands such as Michelin, Pirelli, Avon and Continental, as well as mid-range and budget options. SLSHOP can also supply aesthetically age appropriate tyres that suit earlier cars such as the W113 SL Pagoda and R107 SL. We also offer a tyre balancing service.

• Dim Headlamps

Symptoms

Headlight glass lens cracked, broken or damaged.

Diagnosis
If the reflector inside your headlamps is tarnished or dull, your headlights will appear dim, which in some cases will result in an MOT failure. Reflectors can become dim over time, or be dimmed by damaged cause by water and dirt.

The Cure
1. Headlamp glass only: If only the lens is damaged, new lenses will need to be fitted. The headlamps will need to be removed in order the replace the lenses.

2. Dim reflectors: Replacement with either good second hand units, or we can supply and install new Mercedes-Benz replacements.

• Headlamp wash

Symptoms

Inoperative headlamp/headlight washer system.

Diagnosis
• Corrosion of wash/wipe system

• Damaged washer jets

The Cure
There are two options available to you: we can either restore your headlamp washer system by replacing the broken or corroded elements or, if you prefer, the entire system can be completely removed.

– Radiator Leaks

Symptoms

Leaking and clogged radiators, coolant loss and overheating.

Diagnosis
A particular weakness on all R107 SLs is the radiator’s lack of protection against stones, as well as the radiator core’s tendency to clog up if not properly maintained. 

All SLs engines, from the base 280 six-cylinder to the range topping 560 V8, produce a great deal of heat due to their large capacities, which means the cooling system must also be kept in top condition.

The Cure
If your radiator is leaking or you cooling system is losing its efficiency, we can provide a re-cored or brand new Mercedes-Benz radiator along with a cooling system flush and complete check over. We will also inspect all cooling hoses, jubilee clips and belts to ensure the health of your entire cooling system.

– Poor running

Symptoms

High revving, an uneven tickover, low revving, rough running, flat spots, misfire popping from the exhaust.

Diagnosis
If your car displays any of the above problems and you have eliminated the possibility of an electrical issue (spark/distributor cap/HT leads), then it’s very likely that your fuel system requires attention.

The Cure
Tuning and/or replacement of injection system components.

– Noisy Tappets

Symptoms

A ticking, tapping or clacking sound from the top of the engine. This condition is more often found on just one side of the engine – the driver’s side for UK cars, and passenger side for US and European SLs, but can also be found on both sides. 

This tappet (lifter) noise can be very annoying and spoil the performance of an otherwise healthy V8 engine, making it sound unhealthy or worn.

Vehicles affected
Any SL with a V8 engine.

Diagnosis
Worn hydraulic tappets/rocker arms which, in the worst case, will have affected the camshaft(s). This is due to infrequent or missed oil and filter changes, or the use of an incorrect grade of engine oil, causing oil starvation at the top of the engine, or sludging of the cylinder head oil ways.

The Cure
Treatment of the problem depends on the severity of each case.

1. An oil and filter change with the correct grade of oil can clear the oil ways and restore the compression to the hydraulic tappets if they are not worn.

2. Identify and replace any offending hydraulic tappet(s).

3. If the engine is ticking then replacing all 16 tappets (lifters) and rockers arms will rectify the situation.

In worst case scenarios, we would replace the camshaft(s) as well as all of the tappets and rocker arms. For extra peace of mind, we would recommend an oil and filter change. Click here to view our R107 Hydraulic Tappets.

– Distributor cap

Symptoms

Poor running, difficult starting, misfiring and failure to start.

Vehicles affected
R107 SLs with six-cylinder and V8 engines (350SL, 380SL, 420SL, 450SL, 500SL and 560SL). This problem is particularly common on 300SLs.

Diagnosis
• Faulty distributor cap 

• Faulty rotor arm 

The Cure
Replace both components with high quality parts. Some R107 SLs will also benefit from having a full HT lead set replacement. High quality parts are essential for a long term resolution to this problem.

– Windscreen replacement

Symptoms

Water leak, cloudy screen and misting.

Diagnosis
Cracked, chipped, misted or leaking windscreen.

The Cure
SLSHOP is able to remove and refit your car’s windscreen, typically without the need to invest in a new item. However, if your screen has gone cloudy, you will require a new screen which we can also fit for you here at SLSHOP.

– Cruise control

Symptoms

The cruise control will not operate or works intermittently.

Diagnosis
Faulty control box

The Cure
This fault is usually cured by replacing the control box. We can supply new boxes or recondition your current control box for a fraction of the price. In a few cases, additional elements of the cruise control system may need to be replaced.

– ABS light

Symptoms

ABS brake light stays on. This can often be accompanied by poor starting in 300SLs.

Vehicles affected
R107 SL models: 280SL, 300SL, 350SL, 380SL, 420SL, 450SL, 500SL and 560SL. This problem is especially common on 300SLs.

Diagnosis
• This is generally due to a dirty or faulty ABS sensor.

• Damaged and corroded sensor cable.

• 300SL only: You find that your ABS light is illuminated all time time, in conjunction with poor engine starting. This is a common problem which we have rectified on many occasions quickly and cost-effectively.

The Cure
After testing various relays and the ABS ECU, clean or replace the offending cable or sensor.

– Hood mechanism

Symptoms

Unable to open or remove your vehicle’s hardtop or soft top hood.

Diagnosis
• Not following hood release instructions.

• Faulty latch or cable of mechanism.

The Cure
• Soft top: The window winder release handle should be turned anti-clockwise. Then the short chrome lever should be advanced round in a clockwise position. This should then release your SL’s soft top.

• Soft top and hardtop: In some cases, it is possible to release the tops by inserting a large screwdriver under the soft top deck and releasing the catch, but access can be restricted.

– Damp in boot

Symptoms

Dampness in the boot, or water collecting in the spare wheel well.

Diagnosis
• Major corrosion to the boot floor 

• Water ingress 

• Poor boot seal rubber 

• Rear light units are letting in water and need to be re-sealed.

The Cure
Test the seal and lamp surrounds and either replace the boot seal or remove and reseal the rear lamp units as necessary.

– Cabin damp

Symptoms

General dampness in the car, or water collecting in the foot well. In extreme cases there will be excessive water in your footwells.

Diagnosis
• Corrosion to the bulkhead 

• Perished rubber seals

The Cure
Replace seals or repair bulkhead – both of which can be done here at SLSHOP. For more in depth information on bulkhead repairs, visit our servicing page by clicking here. Alternatively, you can read our case study by clicking here.

– Exhaust gasket

Symptoms

An exhaust blow, ticking or chuffing sound from under the bonnet/hood area. Affects the passenger side on UK cars, and the driver’s side on US and European SLs when the engine is running.

Vehicles affected

Any R107 SL with a V8 engine.

Diagnosis

This problem is especially common on late model V8s built from 1986 to 1989 – commonly the 420 and 500SL. The sound may diminish as the manifolds and headers expand, and as the engine reaches operating temperature.

The exhaust manifolds often develop a crack around the exhaust gas recirculation (EGR) valve area. This problem is common on all V8 SLs to some degree.

The Cure
Rather than remove and replace the manifold (a very expensive exercise), SLSHOP has developed a method of braze repairing the manifold in situ. This repair is both permanent and very cost effective.

– Brake fault

Symptoms

Loss of breaking efficiency. Your brakes begin to screech, grate or pulse when pressure is applied to the brake pedal.

Diagnosis

The braking system on an R107 SL consists of four disc brakes – one on each wheel. With time and use, these discs (or rotors) can become warped. When brake pads become too worn, they will make a grating or grinding noise whenever the brake pedal is applied.

The Cure

Regular replacement brake pads is advisable.

– Exhaust systems

Symptoms

Increased exhaust noise, rattles, broken clamps and reduced engine performance.

Diagnosis
The original exhausts on R107 SLs are extremely robust, but even the youngest cars are almost 30 years old. All exhaust systems will deteriorate over time to some degree. This leads to reduced performance, blowing joints, broken clamps, rattles and general corrosion.

The Cure
At SLSHOP, we offer a complete range of SL exhausts from a variety of manufacturers. Whether you require a clamp or a full stainless steel system, we offer the ultimate in fit and forget exhaust systems.

– Wind noise

Symptoms

You may find your Mercedes R107 SL suffers with excessive wind noise or drafts in the cabin from either the soft or hard tops at cruising speeds.

Diagnosis
Running along the inner edge of your car’s soft top are two cables. If these are broken, then wind noise will increase on the move as air rushes into the cockpit.

The Cure
For soft top: Replacement hoods are really the only effective cure.

Hardtop: The first thing to check is the chrome trim alignment. When the top is sitting on the vehicle, these can be realigned to remove associated wind noise.

Both: In addition to the above fixes, both the driver side and passenger side windows can be adjusted to fit more snugly and reduce wind noise.

– Suspension rattles

Symptoms

The Mercedes R107 SL’s suspension is designed to be smooth and comfortable. As it ages, various components start to suffer and you may find that your SL develops a rattle over bumps or knocks, and squeaks when cornering. Often the noise sounds a lot more severe than the issue at hand.

Diagnosis
The common problem areas, especially around the rear suspension components, are worn anti-roll bar links. Anti-roll bar links are a common cause of MOT failure and are a very inexpensive fix. Other areas to investigate are the shock absorbers, coil springs and control arms. Diagnosis of suspension complaints is often individual to each car.

The Cure
The problem part will need to be replaced. It can be quite surprising how the replacement of shock absorbers and coil springs can transform the handling of any R107 SL.

– Bumper Chrome

Symptoms

Rusty, corroded or holed bumper chromes and rear valances on your R107 SL.

Diagnosis
Water and salt thrown up from beneath the car collects underneath the bumpers and supports, and rots them from the inside out. Rear bumper corners are most worst affected. In addition, all Mercedes R107 SLs can suffer with rusty rear valances and rear quarters. These are divided into three sections, but all corrode at around the same rate.

The Cure
The affected section will need to be replaced with new (or high quality second hand) parts. The rear valance panels can easily be replaced with Mercedes-Benz panels as they are bolt-on, non structural items. This repair includes full undersealing of the panels inside and then re-spraying the outer surface to perfectly match the rest of your car.