W124 Coupe Buyers Guide

Discussion in 'General Discussion' started by Mercland, Mar 5, 2017.

  1. Mercland

    Mercland Authorised Forum Sponsor Authorised Forum Sponsor

    Jan 25, 2014
    Nuneaton, Warwickshire
    Lots of Mercedes!
    Hi All,

    Over the years I have written some buyers guides for the popular magazines. I thought they may help here.

    I hope these is no issue with that.

    If there is anything wrong, please dont hesitate to correct me. The final printed versions were heavily scaled down by the magazines. These are my raw words and my opinions based on my experience only.


    All of the W124 coupes are fuel injected. All engines are thoroughly reliable. With age, some will exhibit some age related issues requiring maintenance.

    Across all of the range, it is important to look for oil leaks, good oil pressure and a generally smooth running engine.
    Maintenance is the key to long term sound running.

    The cooling system is an important area to check across all engines. In all UK weathers, the temperature should not climb above 90 degrees at standstill and should sit around 85 when cruising. Any overheating could indicate a worn water pump, a failing viscous fan, a blocked radiator or issues with the electrical side of the system.
    A poor cooling system will quickly lead to head gasket failure.

    All engines use a variant of the Bosch KE Jetronic fuel system. A very reliable system, however with age, the electronic components such as fuel relays, OVP relays or idle valves can have even the most knowledgeable mechanic scratching his head. Diagnosis on these older cars is not like modern cars. Each component has to be tested in a logical but often laborious manner.
    However, in most cases, issues are usually down to dry solder joints or poor wiring.
    The fuel injection and ignition system itself is extremely durable.

    M102 Engine
    The 230CE M102 engine uses a duplex chain drive which does not usually exhibit any wear until it reaches very high mileages.

    Some common issues are split breather hoses causing a poor idle. A stuck idle valve will have the same effect.

    Head gaskets can require replacement with age which is around a £800 job if required.

    If the engine sounds tappy at idle, the hydraulic lifters may need attention.

    M103/M104 Engine

    The M103 & M104 engine uses a duplex chain drive which does not usually exhibit any wear until it reaches very high mileages.

    Wiring Looms to be inspected, these are of the era when wiring looms were biodegradeable and may need replacement if they have degraded. Cost anything between 700-1500 incl labour.
    Poor wiring looms not attended to will lead to failure of the ignition control unit.
    Condition of the wiring loom is easy to spot, just look at the connectors and gently pull back any outer cover. Any cracked or bare wires is a bad sign.
    There are some companies offering refurbished or aftermarket looms which can save a lot on the cost.

    Head gasket is a common problem on these m104 engines. Check for leaks, especially at back of engine. Cost to replace around £1500 if not other damage.

    All of the M104 engined cars (300-24, & 320) can require water pumps at this age, using genuine parts this is around a £600 job.
    Also if vehicle runs hotter than normal, the viscous fan may need replacement.

    The M103 6 Cylinder engine has a common issue with its distributor cap letting in moisture. If the car starts fine but then starts to splutter as it gets warm, this is the issue. Solved by a new distributor cap, seal and rotor arm. It is imperative to change these items regularly with this engine.

    Most models have an engine oil cooler located on the front left side of the car, inside the front bumper. These can corrode and leak oil. This job often requires both the radiator and pipes to be replaced. The job can be tricky and with garage labour will cost up to £750 or so.

    The exhaust system is well made across the range and have been proven to last 15-20 years.
    At this age the system should be inspected for leaks. Parts are still available from Mercedes but not all parts are affordable.
    Many owners choose to replace exhaust systems with custom made stainless steel items, which usually come with a lifetime guarantee and are cheaper than buying a genuine system.

    The transmissions on the W124 series are very strong and well proven.
    The 5 speed automatic transmission is known to have issues with the electronic 5th gear solenoid, therefore it is important to check that all gears are engaging. Remember the vehicle will set off in second gear from stand still. However, the five speed is the preferred choice of long distance drivers for both comfort and economy reasons.
    Of course over the years the gears and clutches can wear.
    Any potential buyer should check that the gear changes are silky smooth and there are no harsh clunks when selecting gear.
    We recommend regular fluid and filter changes.

    The manual transmissions are extremely solid. With age, the selector bushings need replacement to rectify sloppy gear changes. Any whining may be indicative of a failing bearing, which would require the box to be overhauled.

    Any humming noises from the rear could indicate an issue with the differential bearings. These rarely fail but the noise can dampen the jjoy of driving a W124. Reconditioning of the differential is likely to cost between £600-800.

    The W124 Coupe shares many suspension components with the standard W124.
    Hydraulic rear self levelling was optional on the coupe models. Front shock absorbers are a serviceable item and are not expensive. Various aftermarket options are available.
    Front Lower suspension arm ball joints are a wear and tear item that should be checked for excess play. This requires replacement of the complete suspension arm. These should be replaced in pairs. A garage should charge between £7-800 for this work using good quality parts.
    The self levelling rear suspension, where applicable, is a little more complex and does require close examination. The pipework should be examined for corrosion. These, like brake pipes, can corrode and leak. The pipes are available from Mercedes, however fitting some of the lines around the rear axle takes time and patience. Rear suspension spheres are a common replacement item which will cause a bouncy uncomfortable ride. These are approximately £200 each from Mercedes. Including fluid and fitting charges, this is around a £600 job. Aftermarket parts are available a little cheaper. Once this job is done, the car should not need them replaced again for at least 100K miles.
    The rear shock absorbers have been known to become noisy or leak. Replacement is straight forward but they are pricey. Aftermarket items are around £350 + VAT each.
    Due to age, all of the various ball joints and suspension links should be examined closely. The rear lower ball joints in particular are often missed during inspections however they are prone to fail, causing a knocking noise. Special tools are required for this job and a garage would likely charge £300 per side for this work. The five link rear suspension is also worth replacing if it has not had any attention. All the arms/links are available and not too pricey individually, however to complete a refresh of both sides would cost around £800 using genuine parts.
    Wheel bearings should be checked for excess play. Front bearings can be adjusted. Rear bearings cannot be adjusted and replacement is a labour intensive job.
    Rear subframe bushes should be checked. Deteriorated bushes will cause knocking and will be an MOT failure. Replacement is an expensive laborious job due to the complete axle having to be dropped down.


    Steering is a recirculating ball system. With age and mileage, the steering box can leak or have excess play. Plenty of used spares are available. A recondition will cost around £500-700 with labour.
    A ‘wandering’ or vibration in the steering usually means the steering damper is worn out. In our experience, steering dampers normally require replacing at around 100,000 miles or 10 years. They’re relatively cheap and help to regain steering feel.
    All of the steering links should be checked. Play in the ball joints of the centre track rod and both outer rods is common but relatively inexpensive to repair.

    Brakes and wheels

    The W124 uses brake discs all around. The system is generally reliable and the parts are good value from the main dealer.
    Brake lines should be checked for corrosion, the rear pipes are difficult to replace as they run above the subframe.


    With age, all vehicles will be prone to corrosion. The wheel arches should be examined closely.
    Any minor paint bubbles can normally be ground back and repaired.
    It is important to examine the car thoroughly for rust, especially on the underside.
    We recommend wax protection in order to keep the underside and suspension rust free.
    A full respray will run into many thousands depending on level of corrosion, therefore it is very important to check the car over in this respect.
    The coupes can suffer with delamination of the rear windscreen. IF this has happened, it is likely metal underneath the window seal may need attention.

    The electrics on this model do not generally cause many issues. The engine wiring harness is the major concern, which I have mentioned above.
    It is important to check the function of every component. Items can fail due to age and although most items are available from Mercedes, prices are not always palatable.
    Seats should be checked for all of their functions, electric windows should be fast and smooth. Sunroof should glide back without any nasty noises.
    The seat belt butler should deliver the seat belt without hesitation when the door is closed.
    The seat backs should lock into position with the doors closed and transmission in drive.
    The Air Conditioning system should be examined for proper function. Due to age, leaks in the system are common and electrical such as the fan switches components can fail. The most likely leak point is the condenser, this is available from Mercedes. Cost of replacement will be around £600 from an independent garage.

    Indicative Job prices (including labour and VAT):

    A service (four/six-cylinder)
    B service (four/six-cylinder)
    Gearbox service, fuel filter (300CE/E320, 36,000 miles)
    Cylinder-head gasket (E320)
    Wiring loom replacement (E320, pre/post 1995)
    £750-£1200 depends on options
    Water pump and belt (four/six-cylinder)
    £600 both similar priced
    Front brake discs and pads (four/six-cylinder)
    Engine mounts (four/six-cylinder)
    [FONT=&quot]£550 [/FONT]
    10 people like this.
  2. DanMorgan

    DanMorgan Hardcore MB Enthusiast

    Mar 7, 2012
    R129 300SL 24V, W124 300CE, W210 E55 AMG, W140 S280
    Good information there

    I wrote an article on the possible common problems of the W124

    May have gone overboard but a full covering of potential problems!
    Last edited: Mar 5, 2017
    2 people like this.
  3. grober

    grober MB Club Veteran

    Jun 22, 2003
    Perth, Scotland
    W204 C200CDI Estate

    Just a few suggestions/ additions/ corrections which folks might find useful. Hope you don't mind Jay. :dk:
    Last edited: Mar 5, 2017
    4 people like this.

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