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Mercedes R129 Buyers Guide

Discussion in 'General Mercedes-Benz Related Discussion' started by jaymanek, Mar 5, 2017.

  1. jaymanek

    jaymanek Senior Member

    Likes Received:
    Nov 22, 2002
    Nuneaton, UK
    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.

    H Hood operation should be smooth. At this age the many sensors and micro switches can cause issues. Fault finding, especially on early models which do not communicate so well with diagnostic equipment, can be very time consuming even for a an experienced garage. The hood should raise and lower smoothly as should the roll over bar.


    Rear Soft top windows if cracked or hardened will cost around £800 to replace all three pieces at a good soft top specialist. A worn hood will cost anything between £1500-£2000 to replace at a hood specialist. We recommend either a genuine Mercedes Hood or an original quality hood as aftermarket hoods often exhibit a visibly poor fit leading to leaks and excess wind noise.

    - Avoid models with the ADS Suspension if possible. This is a fantastic system when working correctly, however this system is known to have issues on both the electrical and mechanical sides. Parts are expensive and again early cars are difficult to diagnose.

    - Rust around wheel arches, especially front needs to be checked for.

    - All electrics should be tested thoroughly. Electric memory Seats are a common failure, we replace the control modules under the seat frequently, good news is there seems to be a good used supply at present.

    - A/C should be checked for operation. Normally a non functioning system means a leak for which the usual suspect is the condenser.

    - Early cars with 6 cylinder cars had an optional five speed transmission. This transmission is known not to be as reliable as the four speed. The most common issue is shifting into fifth which is usually an electronic issue not mechanical. However used transmissions do still seem to be available on the used market at reasonable prices and at worst case, a rebuild normally costs around £1500 at a transmission specialist.

    - The 24 valve 300 engines are known for head gasket trouble, this is around £1500 for a repair when required.

    - The 300-24 valve is also known to go through Distributor Caps. Also the seal and backing plate behind the cap may also need replacement if moisture is getting into the cap. This is a common issue.

    - All of the M104 engined cars (300-24, 280 & 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 V8 models are fairly solid mechanically, just check for a smooth power delivery and a steady idle. Early cars use a rotor arm, distributor and leads which are service items often neglected. Later cars use coil packs which rarely cause issues.

    - The Later M113 V8 models (circa 97 onwards) suffer from Crank Sensor Failure which will cause poor hot starting and may even cause the car to cut out when driving. Not an expensive job but one to know about as it could leave you stranded. We recommend changing these if they haven’t been replaced.

    - The V12 model, whilst absolutely sublime to drive, can be expensive to maintain. Head Gasket issues have been reported which is an engine out job and many thousands £ to fix.


    Service history is important if you are looking to retain future value. Whilst knowing what previous work has been carried out is important, we always recommend a new owner invest in changing all fluids, filters and spark plugs for peace of mind.

    The Transmission Service is something that is quite often skipped. This can lead to poor gear changes or even transmission failure. Most specialists will charge under £200 for a transmission fluid & filter change, we recommend it is done at least every 40,000 miles and the Transmission Fluid level should be checked at least at every service. .


    Overall, a good thorough inspection of all the moving parts is necessary. If everything works as it should and the car drives smoothly then hopefully you will be onto a good one. A Specialist pre purchase examination is always recommended!
    Ray Wiliams and mpfrombe like this.
  2. Pullman

    Pullman Senior Member

    Likes Received:
    Jun 16, 2014
    Your Mercedes:
    1981 500SL_1999 500SL_2002 CL600
    Couple of R129's on the Anglia classic car auction January 2018.
    MichaelDavis likes this.
  3. davemercedes

    davemercedes Senior Member

    Likes Received:
    Jun 15, 2012
    Your Mercedes:
    2007 Merc 220 CDi Est Auto Av
    Your point about the transmission service is well made, Jay. I was shown the "ASSYST" heading on the service book and there was some confusion about the transmission being "sealed for life". It was only through question posts on here that I woke up to the fact that my S203 transmission had not had the fluid changed. The cost of a service every 40K miles is a lot less than a replacement auto box!
    jaymanek likes this.
  4. Richard Moakes

    Richard Moakes Senior Member

    Likes Received:
    May 19, 2002
    Newton Abbot, Devon, UK
    Your Mercedes:
    1991 R129.066 M119.960; 2005 W164.175 M113
    Jay, I have to take issue with that statement, ADS-1 can be diagnosed and repaired with nothing more than an understanding of hydraulics and a blink code reader, and I speak from personal experience in that matter, having repaired both my car and another members car.
    Capra likes this.

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