Faults:

Rear suspension going bad is a major problem on these cars. If the W140 is equipped with the self leveling system in the back, the accumulators usually go bad and cost $130 per pair; this assuming your rear struts are not leaking hydraulic fluid. If the struts in the back are leaking, they cost $600 per pair. Front Suspension is like any other car on the W140, shocks & springs.

Additional info from what I know:

The W140, the S600 and S500 comes standard with hydraulic suspensions in the back. The S320 and S420 have the hydraulics (aka SLS - Self Leveling System) optional. Most S320s and some S420s come with normal shocks in the back.

The transmission is known to go bad before you hit 120k miles. This is not usually a forward problem, but the reverse slipping. This is due to the reverse clutch plate, aka the B3 plate wearing out fast. A full rebuild from MB is $3500-2500. I would rebuild the tranny myself; just buy the kit online for $250 and do it yourself. It's really easy. No need to drop the motor, only remove the muffler and the tranny drops right out. The rest is easy, look for videos online.

Additional Transmission Info from what I know:

The trannys on these cars are numbered. Mine is a 95 S500, which means it has a 722.3 (look the back of owners manual for engine & tranny number). This is a mechanical 4 speed auto tranny. The 91-95 have almost same transmissions. The 96+ trannys change numbers, like the 722.5 or 722.6. Both these tranny's might fit on the motor, but they are for a newer production W140 96-99 and will not work with your pre-96 version. This is due to a new control module put in the 96+ w140s controlling the transmission & motor together. Remember pre-96 trannys are mechanically controlled with the throttle/pedal cable. A swap might be possible, but I would have to check myself before I rebuild my transmission this winter.

Car will run HOT. Hotter than any car you've ever driven. This is usually the V12 6.0L or the V8's 4.2 or 5.0, they get really hot. It's common to see the car running at 105 with the A/C on, even while cruising on a windy day. To fix the problem, you need to solder a resistor (1000 ohms) which triggers the fans at 90 degrees instead of 100. This will make your car run cooler. This is a safe procedure; if the resister fails, it triggers at 100.

The rest are stupid problems that might cost a bunch if you abuse your car.

Pre 95 W140's are known for bad electrical system, cables melting etc. This also depends on the location you live.

Evap problems - The nightmare of all W140's. Just hope you don't get this problem, but if you do, there is a DVD someone made, you will have to take the dashboard apart. Following the instructions, will help you take everything apart in 2 hours. The rest is history.

I read the 6 cylinder 3.2 has some head gasket problems. The V12 also has some common running problems. Usually having only one bank working and running only on 6 cylinders instead of 12.

Window regulators, I only got the car with the driver's side regulator broken. The others work fine, but I hear they do go bad. About $40 on ebay per regulator + time to put them on.

Head rests go up and down, but when people use the buttons and play with them, sometimes they bring them down too far, and break the clip that controls the headrest.

The back sunshade is known to get stuck on the upper position.

The side mirrors won't fold. This is due the drivers actually not folding their mirrors in when they park the car. Mirrors don't get used, lose the lubrication, and get stuck or move only an inch when you want to fold them. Use your hand, and someone press the button and flip em in and out a few times.

Sunroof, needs to be lubed up with good grease so it won't quit on you. Do it only once in 3-4 years, and you should be fine.

General Comments:

This is not my first Mercedes Benz, but it one of the best I've ever known.

The S500 I have is fully loaded to the bone. I mean to the bone.. And it's all standard.

- Reclining rear seats.

- Heated front and back seats.

- Up and down rear reclining headrests. Control from the driver and the back passengers.

- Power rear sunshade.

- Heated side mirrors.

- Power side mirrors, powered folding.

- Power rear view mirror.

- 3 different memory sets - front driver and passenger seat.

- Front seats have the bottom section of the seat move separately from the whole seat.

- Windows are all powered.

- Windows are one touch up and down.

- Window stops rolling if there is an obstacle in the way.

- Windows are doubled and thick. Some W140s have bulletproof glass.

- Integrated phone in the glove department. You can get connected with Verizon for $10/month.

The car is amazing, but when it comes to fixing things, it's not cheap. My father is a mechanic and I can afford the fixes for the most part of it, but this car is not perfect.

Due to its heavy weight, wear and tear of the main bearings needs extra attention, same with the transmission and motor. A lot of the extras in the car, although they are special options to have, they will be a problem at one point.

I'd be more than happy to help anyone with further information amuca@oakland.edu

Faults:

Interior display lights fail occasionally due to faulty lighting contact. Easily fixable.

Suspension needs changing.

General Comments:

Absolutely no regrets buying this car.

Had done a fair bit of research on the W140 before purchasing it and was careful to choose a good car.

Found this beauty which is in almost perfect condition overall except for the expected wear and tear items like the bushes and suspension.

Handles like a luxury car should.

It is commanding on the road and other motorist give way when they see it coming up in their rear mirrors!

Travelled on various types of road conditions and in absolute control whatever the condition is.

Having owned a W126 before this car, I can say that this is better than the W126 in many aspects.

I look forward too many years of trouble free usage of this excellent S320L.