The contact owns a 2004 Mercedes-Benz SL500. The contact stated that after starting the vehicle, the message "Brakes Reached Historic Threshold" was displayed, which indicated that the brake control unit had malfunctioned. Additionally, while depressing the brake pedal, the brake pedal was spongy, causing the stopping distance to become extended. The vehicle was taken to the local dealer and was diagnosed with brake control unit failure. The contact was informed that the brake control unit needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure, but no assistance was provided. The contact stated that a 25-year warranty for the failure was previously issued by the manufacturer that was associated with the failure, but was not honored. The failure mileage was 62,800.
The worst 2004 Mercedes Benz SL500 problems
Ranked by number of owner complaints. Mileage and cost come from what owners wrote.
Problems by type
Tap a problem to see which part fails, at what mileage and in which other years.
- Suspension21
- Brakes11
- Fuel system9
- Electrical4
- Transmission3
- Wheels3
- Acceleration2
- Airbags1
- Body1
- Driver assistance1
- Engine1
- Steering1
Specific symptoms reported on the 2004 Mercedes Benz SL500
Recalls
No recalls on record for this model year.
Defect investigations
Air suspension system failure
The subject s-class vehicles contain a compressed air suspension system that uses air struts on each of the four wheels in lieu of traditional springs and shock absorbers.these air struts use compressed air to support the weight of the vehicle and control ride height.in the event of the loss of air from the system, an alert will flash on the instrument cluster warning the driver to either drive carefully or to stop the vehicle.the vehicle ride height can be reduced by as much as 105 mm below normal ride height before the full load of the vehicle for that wheel comes to rest on a steel rod, with a rubber stop on the end, located in the shock absorber.this rest-stop condition is designed such that there is no impact on vehicle control.mercedes-benz (mbusa) supplied video showing a vehicle in this condition operating under several different situations including evasive maneuvers demonstrating the ability of the vehicle to be controlled effectively with a ride height reduced to the minimum.only those complaints to odi and mbusa that alleged a steering interference during a reduced ride height condition were counted in this resume failure report.some complaints alleged that with a reduced ride height and a stop now warning message there was a rubbing noise when turning, but the ability to steer the vehicle was not compromised.a sampling of warranty claims submitted by mbusa did not reveal any indicating a loss of control due to an airmatic system failure.there was one crash reported by mbusa to odi but the information available indicated that it related to suspension systems and it was not possible to verify that the incident was related to an airmatic system failure. Further use of agency resources in this matter does not appear to be warranted.the agency will continue to monitor complaints and other information relating to the alleged defect in the subject vehicles and will take further action in the future if warranted.this preliminary evaluation is closed.
PE07042
Technical service bulletins for the 2004 Mercedes Benz SL500 51
Bulletins tell dealers how to fix known problems. A warranty extension means the manufacturer pays for that repair for longer.
- The warranty on the SBC Hydraulic Unit for MY 2003-2006 Model 211, MY 2006 Model 219, and Model Year...
- Repeat workshop visit for vehicle vibration while braking from 60MPH. NOTE: Although the symptom is...
- Clanking noise from the area of the speakers in the doors
- Single throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end)
- There are several types of complaint about noises or poor windshield wiper wiping performance: A: Wiper...
- Headlamp, front fog lamp leaky or fogged
- Headlamp, front fog lamp leaky or fogged
- Headlamps leaking or fogged
- Single throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end)
- Headlamp, front fog lamp leaky or fogged
2004 Mercedes Benz SL500 fuel economy
Official EPA estimates in miles per gallon (MPGe for electric). Ranges cover trims that share the same engine.
| Engine | Drive | City | Highway | Combined |
|---|---|---|---|---|
| 5.0L 8‑cyl | RWD | 14 | 21 | 17 |
What 2004 Mercedes Benz SL500 owners say
Most recent owner complaints, unedited.
Question 1: The Sensotronic Brake Control (SBC) unit, which is a high-pressure "brake-by-wire" hydraulic system. Component A7/3. The component is currently installed in the vehicle and is available for inspection. Question 2: The vehicle experienced a sudden, catastrophic loss of hydraulic brake pressure while in operation. This failure required extreme physical force on the pedal and significant increase in stopping distance. The vehicle is currently in my garage with chocked wheels until I figure out what's next. A couple days ago, I had the car at a dealer and requested a review of this system and they released the car back to me stating the system status was, "OK" despite me stating to the dealer that the safety-monitoring counter was found to be at 0 on a 63,000-mile car. In all of my research, I believe this "silenced" the vehicle's ability to provide a timely service warning (Code C249F) before total hydraulic failure occurred. Question 3: Mercedes-Benz of Denver performed a diagnostic on January 21, 2026. While the dealer initially claimed the system was "OK," the total failure occurred within 72 hours of their inspection. The reason it was at Benz of Denver is because my independent mechanic confirmed the 0 actuation count which was suspicious to me. I wanted to understand the mechanical integrity of the newly purchased vehicle. Question 4: Yes, inspected by an authorized Mercedes-Benz dealership technician on January 21, 2026. Question 5: To my knowledge there were no mechanical symptoms prior to the red screen however, I cannot confirm or deny that as I had driven less than 1000 miles since I purchased the vehicle. I have no concept of how the braking "should have" felt. The only "symptom" was the technical data anomaly (the 0 actuation count) flagged by an independent shop, which I can attest the dealer refused to investigate fully. On January 24th, 2026, the RED dashboard warning appeared: "Reduced Brake Effect - Start Engine!".
The 2003-2006 R230 series seem to have a problem with the BCM (Battery Control Module) as start an electrical fire in the trunk. Very common issue and a safety hazard - this is what happened with my car. Vehicle has dual battery, starter in front, convenience battery in trunk and fuses that operate at 130 Amps - the BCM capacitors and circuit board age and at some point can no longer handle the high current and catch fire.
On many 2003 and 2004 models. Broken fuel tank baffle inside fuel tank. This is well documented and could possibly cause explosion.
On july 22, 2020 the vehicle (2004 mercedes-benz sl500 (r230)began making a loud banging noise in the rear when stopping and turning. I delivered the vehicle to a local shop where the vehicle was diagnosed as having a broken baffle in the fuel tank. The only solution is to replace the entire fuel tank. Many other owners of this model have experienced the same issue and is clearly a manufacturer defect; this cannot be caused by excess wear on the vehicle. Because there is now a large section of the fuel tank freely swinging inside, there is a chance that this could cause a spark and subsequent explosion. I cannot safely drive this vehicle until the fuel tank is replaced at a very large cost. This model should have been recalled when this issue was first coming to light over 15 years ago.
Tl* the contact owns a 2004 mercedes-benz sl500. The contact stated on various occasions while his vehicle was stationery and in park, either the right side or the left side of the vehicle would raise up then descend to ground over a thirty second period independently without warning. The contact also stated that the hydraulic fluid leaked out of the engine. The vehicle had yet to be taken to a dealer to be diagnosed or serviced for the failure. Upon investigation, the contact linked his failure to the federal safety agency campaign number :08v405000 (suspension) however, the VIN was not included in the recall. The manufacturer had yet to be notified of the failure. The vehicle had yet to be repaired. The failure mileage was approximately 92,000.
I experience a strong odor of fuel when entering my vehicle and when driving the vehicle, also when driving the vehicle I heart a loud thumping sound coming from the trunk area. Sounds to me as though something is floating inside gas tank. This odor has sickened me and has severely upset my stomach to the point that I'm unable to drive my vehicle except for a short distance. The thumping sound is created when vehicle is moving or coming to a stop but happens continuously while driving.
The vehicle has a bracket on top of the gas tank that comes disengaded and causes this distinctive noise which sounds like something swinging and tapping against the gas tank and I has to happen a lot due to every service I have been asked about the problem. It also has to be something with multiple vehicles due to online mercedes owners are having the same problem. The sound is really disturbing and I would like an answer as to what to do. Thanks [xxx] information redacted pursuant to the freedom of information act (foia), 5 u.s.c. 552(b)(6).'
I submitted via fax earlier this week a formal letter to mr. Exler the president & ceo of mbusa and, cc'd mr. King of the federal safety agency that included information about known critical safety issued these vehicles had prior to mbusa importing them to the united states. Mbusa failed to disclose these known issues and, chose to importation these vehicles violating vehicle importation rules. Yesterday-january 31, 2019 I received a call from a representative of mbusa stating he was calling on behalf of mr. Exlers office concerning my letter. I will not be intimidated by mbusa while seeking the truth on why mbusa allowed these vehicles to enter the USA knowing these critical safety issues existed while misleading consumers and, the federal safety agency. On january 21, 2019 my vehicle had what is described by mbusa as a catastrophic failure when the entire brake system failed. This failure could have killed me - and, other motorist. Mbusa has replaced the sbc unit at least 6 times and, still the issue and, other persist. The vehicle has been driven on average 4,000 miles annually. How many failures must happen before mbusa is fully investigated? They refused to provide me any information on the vehicles except the 4 year warranty period. Once I complete my research on these vehicles I will submit my findings to the federal safety agency & ms. King
Tl* the contact owns a 2004 mercedes-benz sl500. When the vehicle was started, the contact heard an abnormal knocking sound underneath the vehicle near the fuel tank. Additionally, there was a constant fuel odor inside the vehicle. The vehicle was taken to mercedes-benz of virginia beach (located at 4949 virginia beach blvd, virginia beach, va 23462, (757) 499-3771) where it was diagnosed that one of the baffles in the fuel tank fractured, separated, and needed to be replaced. The vehicle was not repaired. The manufacturer was not notified. The approximate failure mileage was 144,000. The VIN was not available.
Compare the 2004 Mercedes Benz SL500
Other model years
199219931994199519961997199819992000200120032004200520062009
Questions about the 2004 Mercedes Benz SL500
Is the 2004 Mercedes Benz SL500 reliable?
Owners have filed 45 complaints about the 2004 Mercedes Benz SL500, 2.4 times a typical SL500 model year.
What is the 2004 Mercedes Benz SL500 year score?
The 2004 Mercedes Benz SL500 scores 38 out of 100 (poor). The score compares it with the other model years of the Mercedes Benz SL500: 75 is a typical year, 50 means twice the usual complaints, and serious complaints and recalls lower it.
What is the most common problem with the 2004 Mercedes Benz SL500?
Suspension, with 21 complaints, typically around 56,000 miles. Next is brakes (11).
How many recalls does the 2004 Mercedes Benz SL500 have?
No recalls on record.
What year does the Mercedes Benz SL500 have bad suspension?
The Mercedes Benz SL500 model years with the most suspension complaints are 2003 (34 complaints) and 2004 (21 complaints).
What gas mileage does the 2004 Mercedes Benz SL500 get?
Official estimates for the 2004 Mercedes Benz SL500 range from 17 mpg combined. The most efficient version (5.0L 8-cyl, RWD) gets 14 city and 21 highway.
VIN decoder
See the problems and recalls for an exact car
Buying a used 2004 Mercedes Benz SL500?
Check the exact car before you pay: accidents, salvage or flood titles, odometer readings and previous owners.
Check its history