AI DamageMercedes-Benz 420: problems, complaints, bulletins
Summary for the Mercedes-Benz 420 across 12 model years: 79 owner complaints and 0 NHTSA service bulletins, plus repair videos. Pick a year for details.
Model years
What fails most often
- 1 Electrical system 18% of all complaints
- 2 Suspension 16% of all complaints
- 3 Service brakes 9% of all complaints
- 4 Powertrain 8% of all complaints
- 5 Vehicle speed control 8% of all complaints
- 6 Engine and cooling 6% of all complaints
- 7 Fuel system 6% of all complaints
- 8 Air bags 5% of all complaints
- Electrical system: 14 complaints (18% of all).
- Suspension: 13 complaints (16% of all).
- Service brakes: 7 complaints (9% of all), 2 of them with a crash reported by the owner.
- Powertrain: 6 complaints (8% of all).
- Vehicle speed control: 6 complaints (8% of all), 3 of them with a crash reported by the owner.
Engines and transmissions
US-market versions per EPA. On the right: how many NHTSA complaints name this engine or transmission type.
- 4.2 L · petrol · 8 cyl 1986–1991
- automatic, 4-speed 1986–1991
Drive: RWD
Symptoms owners describe
How many of the 79 NHTSA complaints mention each symptom (automatic count from complaint text; one complaint can mention several).
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Electrical system | 14 | 0 | 0 |
| Suspension | 13 | 0 | 0 |
| Service brakes | 7 | 2 | 0 |
| Powertrain | 6 | 0 | 0 |
| Vehicle speed control | 6 | 3 | 0 |
| Engine and cooling | 5 | 0 | 0 |
| Fuel system | 5 | 0 | 0 |
| Air bags | 4 | 4 | 0 |
| Child seat | 4 | 0 | 0 |
| Equipment | 4 | 0 | 0 |
| Seat belts | 3 | 1 | 0 |
| Structure | 3 | 0 | 0 |
| Visibility | 3 | 0 | 0 |
| Exterior lighting | 2 | 0 | 0 |
What owners report
Short excerpts of NHTSA complaints in the original wording. These are owner statements not verified by NHTSA; personal data removed.
The driver's side air bags did not deploy when the consumer was involved in an front end collision with his 1991 mercedes benz 420 sel. ****
The problem started last august. It occurrs only occasionally and has never been duplicated when at a dealership or repair shop. After applying the brakes and coming to a stop, the car starts to roll forward. When I take my foot of the brake pedal and reapply it, the car then stops.
During impact, front seat belt on driver's side failed to restrain driver. Also, caused driver's breast implants to rupture. Other passenger failed to wear seat belt. But, air bag deployed.
Fron parked position, when vehicle put in gear, car lunged forward at high speed without engaging accelerator pedal. Break would not stop car.
Got in the vehicle, started the ignition, and vehicle accelerated during 80 mph on wet pavement. Vehicle kept spinning around and around and slammed against the curb and bounced back and forth against the curb. Also, wheel came off and vehicle ended up in consumer's yard between an oak tree and a telephone pole.
No deployment of drivers air bag in accident, causing injuries.
When owners complained
NHTSA complaints by filing year. The peak shows at what age the problems show up most.
What to check before buying
- Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
- Suspension. Wheel alignment, control arms, subframe, even tire wear.
- Service brakes. Pedal feel, ABS operation, leaks, discs and hoses.
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
Other models of this make
Read also
Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-05.