Consumer Guide's® Auto Editors have scoured repair bulletins and questioned mechanics to search for commonly occurring problems for a particular vehicle. In some cases we also give possible manufacturer-suggested solutions. In many instances these trouble spots are Technical Service Bulletins posted by the manufacturer, however, we have our own expert looking at additional vehicle problems.

Automatic transmission: The transmission may delay shifting into Drive or Reverse, and may be corrected by installing reformulated Mercedes-Benz transmission fluid. (1990)

Automatic transmission: Harsh and erratic shifts are often due to a damaged dust cover on the vacuum modulator for the transmission. (1990-94)

Brakes: Brake squeal at low speeds (under 10 mph) may activate the antilock brake system. (1990-93)

Clutch: Sticking clutch pedal on 300 SL could be due to fluid boiling in the slave cylinder. (1992)

Convertible top: The locking tabs for the convertible top tend to wear and should be checked every 15,000 miles. (1990)

Exhaust system: Possible exhaust leak at the oxygen sensor caused by damaged catalytic converter. (1990-91 diesel)

Hard starting: Hard starting, misfires, and poor drivability could be due to insulation flaking off of underhood wiring harness. (1990-95)

Oil leak: Oil enters the air filter. There are revised valve covers with improved oil separators available for the 3.0-liter engine. (1990)

Rough idle: Stretched timing chain may cause noisy engine, rough running, hard starting, power loss, and oil loss. (1992-94)

This table lists costs of likely repairs for comparison with other vehicles. The dollar amount includes the cost of the part(s) and labor (based on $50 per hour) for the typical repair without extras or add-ons. Like the pricing information, replacement costs can vary widely depending on region. Expect charges at a new-car dealership to be slightly higher.

1990 300: Bolts used for brake-strut support do not meet specification and may break, resulting in deterioration of steering and braking.

1990 300: Under certain operating conditions, plastic cover of preresistor for auxiliary fan may melt, which could result in underhood fire.

1991-92 400E: If car is restarted soon after shutoff and charcoal canister is saturated with fuel, fuel vapor may be expelled onto electric-auxiliary radiator-fan preresistor; under certain conditions, that preresistor could become hot enough to ignite the fuel.

1992 w/"ASR" automatic slip control: Plastic brake-hydraulic hose was misrouted too close to preresistor for auxiliary cooling fan, which becomes hot under certain conditions; could cause hose to melt and leak brake fluid onto hot preresistor, resulting in possible fire.

1992-95 E Class 124: Front passenger metal footrest can, over time, abrade through wiring harness, causing short circuit; wires might then overheat, engine may stall, or airbag could inadvertently deploy.