I bought my 03 SL500 5 years ago and it had roughly 70,000 miles on it. The 1st issue was a plastic part in the shifter box, almost got stuck in San Diego when it broke and it would jot shift into any gear, so looked it up and followed the directions, I took the shift knob off and beat the shifter with a 3lb slept and smacked it a few times and it did allow me to shift ( just make sure you do not put back into park ), once home pulled console apart, took shifter box out and replace broken plastic with a replacement made from alluminum one and put it back together. The next issue was with the suspension, had the dash light up a few times telling me car was low but it wasn't, then had RR shock leaking and they said they wanted 1600 for a shock, actually found a place that makes a conversion coil over, so I did that on all corners, they new suspension cost me 1200 and they bought the old shocks back from me for 400 each, so now it's in sport mode all the time ( I live in AZ and will not be driving in snow or putting chains on ). Replaced the AC compressor, so that was a grand, and now I had an altornator go out and also took the BCM with it so between those 2 parts it's about 1100. So all in all it hasn't been any worse then any other vehicle, but it sure is a lot more fun to drive and gets way more looks and compliments, I spend most of the week driving a F150 of F350 so getting in the car that small and that close to the road is a big change ------ it's a nice toy
I have owned this car for almost a year now, and I was expecting it to cost 3-5k a year to maintain. I had an emergency fund in place fully funded and so far it's been in the shop for some ball joints in the suspension, an intercooler pump (which is upgraded so it shouldn't break for a while) and couple of new rims because the 2 left got bent. I've replaced the alternator, crank shaft position sensor, engine and cabin air filters, a few pulleys and a valve cover gasket. It's going to need trunk struts, accumulator spheres, engine/transmission mounts and a few cosmetic touch ups (but overall my car is in really good shape). This car has costed me $2,000 in the first year to get caught up on maintenance which is cheap for a car like this at 14 years old. The engine was shutting off on it when it got warmed up not too long ago. I was able to diagnose the problem in less then 15 minutes at a cost of less then $28. It was the CPS and it was a breeze to install once I got it (took 10 minutes) and every local auto part shop had it in stock. I replaced the alternator myself on it as well and once you know the procedure it's easy to replace. You need to remove the fan shroud and it will make it easier but it was a breeze as well. This is a very easy car to work on. The hood opens 90 degrees and theres a lot of room to work almost like an old muscle car. The struts and brakes cost a lot retail but you can find them so cheap to nothing if you shop around so the parts are usually very cheap and sometimes free in my experience if you send the old ones in. The engine parts are almost all metal and you don't have to worry about anything breaking unless you over tighten stuff. The car gets terrible overall fuel economy but it's very fast and the acceleration is brutal in a way. There are a few quality problems but they're very small and the average person wouldn't be able to find them. The quality of materials and build quality is overall extremely high for this vehicle especially when you consider it's from the DaimlerChrysler era. It's got a tank like Mercedes-Benz build quality to it. It feels very solid and heavy and the doors are very heavy. The transmissions in these vehicles shift very slow and are a bit cumbersome but are basically the same as you'd find in a Sprinter van or almost any other Mercedes in this time period and is found in almost every V12 Mercedes until 2014 or so. You can also find it in many Chrysler vehicles like V8 Grand Cherokees, 300's, Chargers, Challengers, Durangos, you name it. It's even in some Jaguars and 911's. It's a very heavy duty unit and can run for 100's of thousands of miles. When you need to replace it just make sure it has the correct torque converter and you're golden. The unit should be pretty cheap. This is a very intuitive car. I am not a technician or expert and I can easily diagnose anything in this car in 15 minutes or less. Make sure the hydraulic fluid has been getting changed though before you buy one because the car rides on a fully active hydraulic suspension and one pump runs the suspension and steering. If the fluid is not changed before 50k miles at least, the pump will fail, the lines will get clogged and it can ruin your struts. It can total out your car if someone is careless about this and should be done every 30k along with the transmission fluid or even 20k if you can. This is the only thing you have to worry about. The engine mounts go out early because they're filled with fluid and are soft to make the car ride and settle better so that's normal. Supercharger oil should be done every 20-30k as well and make sure you lubricate the seals and the top. Overall if you listen to what Mercedes tells you to do and do more than what is expected and are good to your car you will be rewarded with one of the most reliable vehicles on the market. 1,000,000 miles on one of these is not uncommon and can go possibly 2,000,000 miles between rebuilds. It's a very solid and simple single overhead cam engine. It's not hard to maintain. Make sure you have an emergency fund in place though. You should have one anyways and it should have at least $12,000 in it.
Not sure about all the negative comments. I bought this car for my wife as she has always wanted a convertible and geez you just can't go wrong with MB. I bought it over a year ago. It was a 2003 with 29,000 miles on it! I bought it in 2016. The car has never been in accidents and appears to have regular maintenance from records. We have put 8000 miles on it since owning it and almost all the original components are on it and have not failed with one exception (see further below). We do not drive it in the Minnesota winter. The car has been near flawless, fun, reliable, extremely comfortable, and surprisingly a good handling car. It's the whole deal. While it does not have the power my RS6 does, nor equal the cornering and braking of my Porsche or RS6....the comfort and styling just can't be matched. I would rather drive this car than the others. I was so impressed with this car I bought an AMG MB days after. The only thing that does not work is the lumbar control in the driver's seat. We are still on the original brake pads and only have had to do one oil change.