faults with r129 sl mercedes

Common Problems R129 SL

Problems and Faults with the R129 SL

The Mercedes SL (R129) was without doubt one of the best cars Mercedes ever built between 1990 to 2003. The floor plan is a shortend version of the W124’s and it also shared many other parts. The R129 went through two facelifts, the first being in 1995 and the second from 1998. The easiest way to tell which facelift is from the design of the rear lights.

The R129 SL was the must have car of the 90’s and was featured in many hip hop/rap videos and even Princess Diana owned one.

The 13 year production run of the R129 came with diverse range of engine options. Starting from the M104 SL280 to the V12 SL600, with the latter being more desirable along with the SL 500 which was a V8.

AMG and Brabus both had ago at tuning the R129, with AMG providing bumper, side skirt and spoiler options. There was even a SL73 that was the biggest engine put into a Mercedes of that era and even bigger than the AMG’s of today.

The predecessor of the R129 is the desirable R107 and the successor is the R230. Due to the little electronics on the R129, it is far less problematic than the R230, which can be plagued with electrical problems.

R129 Rolling Shot
What Chassis is this car?

Common R129 Reliability Problems

  1. Distributor Caps – Early R129’s such as the 300 and 500 suffer damp distributor caps that cause misfires and other gremlins. Ensure you replace these distributor caps with premium brands and if you own the 500SL, there are two distributor caps.
  2. Wiring Loom – Excluding the M103 300 SL and the M104 300-24v SL, the wiring looms are biodegradable and will eventually break, which is not the cheapest of repairs.
  3. Storage Boxes Breaking – Not the most problematic but every SL that ive been in are broken. These are located in the doors and they are either jammed or the clips have snapped off. The storage within the dashboard will 90% of the time be jammed also.
  4. Rust – The R129 is much better than many of the other Mercedes’s of the same period but they do suffer rust on the front section of the front wings.
  5. Roof Operation – The roof is relatively problematic but only when looked after. If the car is left outside during the winter months and getting damp inside, the electrics will start to corrode. The most important electric for the operation of the roof is the roof controller module. These are not cheap to replace and can break for all sorts of reasons. The most popular reason for breaking is by jump starting a R129, NEVER JUMP START this Mercedes SL.

These above are the main common problems with the R129 but other faults may come with old age or poor servicing throughout its life. The R129 overall is a very reliable car and is one of the best Mercedes’s ever built.

R129 Modifications and AMG Upgrades

One of the best modifications you can do if you don’t already have one is buy a wind deflector for the R129. This makes driving with the roof down at high speeds much more pleasurable and will even increase the value of your car.

The R129 SL was a luxury car and if you have driven one, you may feel they are fairly quiet. If you are looking for a louder growl, you can upgrade to an AMG style exhaust that will compliment the rear end of the SL.

All R129’s will (or should) have a hard top in either panoramic or standard form. This is great as you can use the car as a coupe and a convertible but the issue comes when you need to remove it. To risk damage to the roof, we highly recommend that you buy a R129 convertible roof stand to ensure a safe storage. You could even go a step further and store the R129 Roof into a breathable bag to reduce scratches and accidental damage.


Co-Founder & Director of Mercedes Enthusiasts. Current Mercedes: W124 300CE AMG, R129 30024V SL, W210 E55 AMG & W210 E320 CDI.