Common problems with Mercedes W140

The W140 S-Class is arguably one of the best Mercedes sedans of all time and is certainly one of the best full-size German executive sedans ever. The W140 pioneered a bunch of technologies that can nowadays be found in more regular cars such as parking assistance systems, ESP, Xenon headlights, and even soft-close doors.

The W140 is built like a tank and is likely going to become a future Mercedes classic. However, this does not mean that the W140 is completely without fault as that is almost impossible. One of the most common issues with the W140 are the fuel injection harness and A/C compressor leaks, especially on the pre-1996 models.

The PSE (Pneumatic System Equipment) is tasked with controlling the power locks, power windows, and power tailgate, and all of these are known to fail from time to time. The 5-speed transmission did not come with a specific servicing schedule which meant that the chances of failure are greater.

The W140 is an incredibly heavy car which means that the suspension is also prone to issues. This is mostly due to worn-out front and rear coils. All in all, the W140 is indeed built like a tank, and it should last you a long time, but only if you take proper care of it.

 Fuel injection harness issues

The fuel injection harnesses in the pre-1996 models are prone to premature cracking because they are made out of biodegradable materials which are not meant to last forever. Issues such as these are known to cause a short circuit which could potentially cause a myriad of different issues.

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These issues include temporary loss of power, rough idle, stalling or not being able to start the car up at all. Be sure to look for past 1996 models which utilized a more quality-made harness or even the pre-1996 models with a replaced harness.

A/C compressor leaks

Another issue that is fairly common with pre-1996 models is the leaky air conditioning evaporator. This is usually being caused by corrosion forming on the evaporator connections and over time, they tend to create a leak. In order to fix this, you will have to take your W140 to a trained Mercedes specialist because this is a fairly difficult task to do.

The dashboard needs to go out in order to fix this so you should be prepared to leave your W140 in the shop for a long time. This is one of the most stressful issues associated with the W140, but even then, the fix is actually fairly easy to do, but rather time-consuming.

Pneumatic System Equipment issues

The PSE pump is tasked with controlling the lumbar support, the locks, rear parking guides, trunk lid release, and the vacuum to the HVAC servos. However, the pump is also known to fail from time and time, and one way to notice this is if your door locks or power lumbar support system are not working.

The W140 has a completely separate system that controls the innovative soft-closing doors, but this system is also prone to similar issues.

Potential automatic transmission issues

The 5-speed automatic transmission found in the W140 did not come with a specific servicing schedule which meant that you are never 100% sure when to change the oil. If you fail to change your oil at the exact time, you are increasing the chances of causing all sorts of issues down the line.

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As such, be sure to calculate when you had your previous transmission oil change and also be sure to repeat it every 40k miles or so.

Suspension system issues

The range-topping W140 model weighs almost 5000 pounds which means that it is an incredibly heavy car, even by today’s standards. All of that weight needs to be supported by a sophisticated suspension system that needs to sustain the weight in all sorts of environments including bad road quality and aggressive bumps.

The bushes found in the suspension sub-frames are known to go every 150k miles or so, so be sure to pay close attention to these systems. Another suspension issue that plagues the W140 is the front and rear coil component that tends to break after a while. You will sense a significant lack of suspension composure which means that bumps are going to unsettle the car more.

FAQ Section

 Is the Mercedes W140 a good car?

The Mercedes W140 is actually one of the best Mercedes models of all time, and many people deem it to be the best S-Class of all time. Given the fact that the S-Class has always been the flagship of the Mercedes range, and this is one of, if not the best S-Class of all time, it is safe to say that the W140 is indeed a really good car.

The W140 offered so many features and innovations that were unheard of back in the day. Nowadays so many cars benefit from the W140 and the fact that Mercedes introduced so many convenience features with the W140.

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Is the Mercedes W140 a safe car?

The W140 S-Class is indeed a safe car because it was the very first car to introduce electric stability control. No car from that era offered nearly the same amount of safety technology as the W140 which means that even by today’s standards, the W140 is a safe car.

Most crash testing organizations rated the W140 with a top-notch 5-star rating.

Is the Mercedes W140 a future classic?

Large luxury sedans are not exactly the most desirable cars after a few decades, but the very best ones out there, like the W140, could potentially become classics. Indeed, the values of these are still strong and the best examples out there tend to increase in value over time.

So, if you come across a decent W140, be sure to keep it in good condition and with relatively low miles, because it could earn you some money down the line. It’s incredibly difficult to predict if a specific car is going to increase in value or now, but the W140 is certainly going in that direction.

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Marko Mikulic

Why do you love writing about cars? I love writing about cars as cars are a huge personal interest of mine. I was raised in a car enthusiast community and ever since I was young, I always wanted to do car-related work.

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