Which parts fail
Components named in complaints (fuel pump, injectors, fuel tank, hybrid and EV propulsion).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2003 Mercedes-Benz SL500 owners, lightly cleaned up (personal details are redacted by NHTSA).
The 2003 SL500 with seemingly no instigating incident or event had the gas tank baffle come apart due to the poor and faulty design of this component. This baffle now is loose and floats on the gas in the gas tank, banging around when there is acceleration or deceleration, even turning sometimes causes it to bang around. Speed bumps are another source of loud banging from the baffle bumping into the sides of the tank. The issue with 2003 SL500's is ubiquitous, it is not a question of what percentage of them will experience as it appears it will happen to this vehicle at some point due to the poor design and implementation of the baffle. …
Tl* the contact owns a 2003 Mercedes-Benz SL500. While driving into the garage, the abc pump warning indicator illuminated and the contact noticed smoke inside the vehicle. In addition, the contact noticed a large amount of hydraulic fluid on the garage floor. The vehicle was towed to a dealer where it was diagnosed that the front and rear axle valve lock, and pressure reservoir for the abc system needed to be repaired and flushed. The vehicle was not repaired. The VIN was not included in NHTSA campaign number: 07V263000 (suspension, engine and engine cooling). The manufacturer was made aware of the failure. The approximate failure mileage was 55,620.
Here a banging noise behind the seat, took it to a Mercedes Benz repair shop. They informed me the fuel tank baffle is broken free. He said it is very common on this model. But not covered under warranty or recall. It would cont me over 2,500.00 to repair. Doing some research online at mbworld forum. This happen on almost every car like this. I can not afford to fix this. And I am worried this might blow up or something, since something banging around the the inside of the fuel tank can not be safe, this car runs on premium gasoline. It seems to happen louder when the tank is from 3/4 full to 1/2. If I let it run to low the fuel gauge sticks on empty until I go over a big bump. I believe this is a factory defect as the car only has 60,000 miles on it. I should not have to replace the fuel tank on a car that cost about 100,000.00 new. …
Driving along on 2/14/2015, I hear a banging coming from the back of the car. I notice it only does it when I am excelling or braking. I thought there May be something in the trunk, like a liquid with something floating in it, banging up against the side of the container. After I parked, I checked out the box that I have put in the back of my car. There was nothing there that would make this noise. Upon further investigation, I see that there many complaints against the baffle that is inside the gas tank that comes lose and bangs the sides of the gas tank. This is not acceptable. I will take my car to the shop on Tuesday and see about repairs and having mb pay for it.
Tl* the contact owns a 2003 Mercedes Benz SL500. While driving at various speeds, an abnormal noise could be heard in the vehicle. The vehicle was taken to an independent mechanic where it was diagnosed that the baffle in the fuel take fractured and needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 56,408.
Hearing clanging, thump noise between seats and truck, took it to a repair shop and was advised it is a common issue with this model - problem with baffle in the tank and might have come off, searched on-line and found hundreds of complaints for the same issue, was this ever addressed by mb and recalled?
Mercedes-Benz built baffles inside the fuel tank to prevent fuel sloshing noise during stop and go motion. These baffles were poorly designed and weakly welded into place resulting in them coming loose and banging around inside the fuel tank. Being a small convertible and given that fuel tank is immediately behind passenger compartment, end result is a very loud banging noise making driving a slow torture. Aside from irritating loud banging noise there is also a potential of explosion since this is a moving metal part inside a metal fuel tank containing gasoline as both liquid and fumes. There are also many reported instances of this design flaw with some dealers reporting 10 fuel tanks replaced in 1 week. …
1. Events leading up to failure. Driver started noticing "sloshing" sound coming from gas tank area. Next day, a rattling noise starting coming from gas tank area each time the car would come to a stop. The noise was consistent with something floating around and hitting something mental inside. The sound comes from the gas tank area, consistent with a loose piece of metal floating in the gas tank. 2. Upon inspection, the baffle within the gas tank had broken off and was loose, floating in the gas tank. Each time the driver comes to a stop, the baffle will float around and bang on the inside of the gas tank. Preliminary inspection reveals that subsequent model year gas tanks are differently designed to prevent such failure. Consequences of having a loose piece of metal floating around the gas take are extremely serious. …
My Mercedes 2003 SL500 developed banging noise in the gas tank, in January 2010 , having about 18,000 miles, prompting me to call the dealer. I was told that the baffle broke off and couldn't be fixed, advising me to replace the tank for $2,500. I argued that it was an obvious manufacturing defect considering the low miles and requested a free tank replacement, but I was refused on the grounds that the warranty expired. I couldn't believe what I heard, did some research and discovered that early models in 2003 and 2004, had similar tank problems and were replaced with a better design later. But, I was not informed about it. Furthermore, I found out that many other owners from that time had the same problem as I did. …
I have a 2003 SL500 Mercedes . I hear either a free dangling object behind the seats or perhaps a noise from an object in the gas tank (not sure where the tank is). This clanging noise is heard when car is shook. Even a light nudge of the car will cause it to clank. Like a dangling object, hard acceleration will cause the noise to go away but when the car stops accelerating a clanging noise is heard. The car is running perfectly. This May have started happening while my car was parked overnight seeing as though it would have been hard to miss it when parking the night before. I can not rule out vandalism of some sort but I am having a hard time seeing how this could be the case. Mercedes dealer states that there is an anchor that holds the gas tank in place and it has broken, that's why the I get the clanging noise!! …
Fuel System complaints in other SL500 years
Frequently asked questions
How common are fuel system problems on the 2003 Mercedes-Benz SL500?
NHTSA has 20 complaints about the fuel & propulsion system of the 2003 Mercedes-Benz SL500, 25% of the model year's 80 complaints. The component named most often is storage › tank assembly (2 mentions).
Is there a recall for 2003 Mercedes-Benz SL500 fuel system problems?
No. NHTSA lists no fuel & propulsion system recall for the 2003 Mercedes-Benz SL500. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2003 Mercedes-Benz SL500 fuel system problems start?
Half of the complaints with a recorded mileage happened before about 56,000 miles, and 6% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 0 injuries to fuel & propulsion system problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.