Mercedes 240 Workshop Manuals and Repair Manuals

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Mercedes 240

W123 is the internal chassis-designation Mercedes-Benz used for their executive line of cars, manufactured between 1976 and 1985. The W123 models surpassed their predecessor, the W114 and W115 models, as the most successful Mercedes, selling 2.7 million cars before replacement by the W124 after 1985. From August 1977, long-wheelbase versions (3,425 mm (134.8 in)) were produced. These were available as 7/8 seater saloons with works bodies or as a chassis with complete front body clip, the latter serving as the base for ambulance and hearse bodies by external suppliers like Binz or Miesen. These "Lang" versions could be ordered as 240D, 300D and 250 models.

Mercedes 240 FAQ's

How do I change the oil in my Mercedes 240?

To change the oil in your Mercedes 240, locate the oil drain plug underneath the engine and remove it using a wrench. Allow the old oil to fully drain out before replacing the drain plug and tightening it securely. Then, locate the oil filter and unscrew it using an oil filter wrench. Replace it with a new filter, ensuring it is tightened properly. Finally, refill the engine with the recommended oil type and quantity, checking the oil level using the dipstick to ensure it is at the correct level.

How do I check the brake fluid level in my Mercedes 240?

To check the brake fluid level in your Mercedes 240, start by locating the brake fluid reservoir, usually mounted on the driver's side of the engine compartment. Ensure the vehicle is parked on a level surface

How do I check the tire pressure in my Mercedes 240?

To check the tire pressure in your Mercedes 240, start by ensuring the tires are cold. Locate the tire pressure placard, usually located on the driver's side door jamb or inside the fuel filler flap, and note the recommended tire pressure for your vehicle. Using a tire pressure gauge, remove the valve cap from each tire and firmly press the gauge onto the valve stem to obtain a reading. Compare the reading to the recommended tire pressure and adjust as necessary by adding or releasing air.

How do I check the transmission fluid level in my Mercedes 240?

To check the transmission fluid level in your Mercedes 240, start the engine and allow it to reach normal operating temperature. With the engine running, locate the transmission dipstick, usually marked with a yellow or red handle, and pull it out. Wipe the dipstick clean, reinsert it fully, and then remove it again. Observe the fluid level on the dipstick, which should be within the designated range. If the level is low, add the recommended transmission fluid through the dipstick tube, being careful not to overfill.

How do I diagnose a check engine light in my Mercedes 240?

When the check engine light illuminates in your Mercedes 240, it is an indication that there is a potential issue with the engine or emissions system. To diagnose the cause, you will need an OBD-II scanner. Connect the scanner to the vehicle's OBD-II port, usually located under the dashboard near the steering column. Retrieve the diagnostic trouble codes (DTCs) from the scanner and refer to the code definitions or consult a repair manual specific to your Mercedes 240 to identify the underlying problem. Address the identified issue accordingly or seek professional assistance if needed.

How do I replace a cabin air filter in my Mercedes 240?

To replace the cabin air filter in your Mercedes 240, start by locating the filter housing, which is typically located behind the glove compartment or under the dashboard. Remove the retaining clips or screws to access the filter housing, then remove the old filter by sliding it out. Clean the filter housing if necessary, then insert the new filter in the same orientation as the old one. Reinstall the retaining clips or screws to secure the filter housing, and ensure it is properly sealed. Finally, test the airflow from the HVAC system to ensure proper installation.

How do I replace a headlight bulb in my Mercedes 240?

To replace a headlight bulb in your Mercedes 240, start by opening the hood and locating the back of the headlight assembly. Remove the rubber cover or dust cap, if applicable, and disconnect the electrical connector from the bulb. Next, twist the bulb counterclockwise to release it from the socket, and carefully remove it from the assembly. Install the new bulb by inserting it into the socket and twisting it clockwise to secure it. Finally, reconnect the electrical connector and replace the rubber cover or dust cap, if applicable.

How do I replace a spark plug in my Mercedes 240?

To replace a spark plug in your Mercedes 240, start by locating the spark plug wires or ignition coils on top of the engine. Carefully disconnect the wire or coil from the spark plug, ensuring not to damage the connector or wire. Use a spark plug socket and ratchet to loosen and remove the old spark plug from the cylinder head. Install the new spark plug into the cylinder head and tighten it to the manufacturer's recommended torque specification. Reconnect the spark plug wire or ignition coil, ensuring a secure connection, and repeat the process for the remaining spark plugs.

How do I replace a windshield wiper blade in my Mercedes 240?

To replace a windshield wiper blade in your Mercedes 240, start by lifting the wiper arm away from the windshield. Locate the release tab or button on the wiper blade connector, and press or push it to release the blade from the wiper arm. Slide the old blade off the connector and discard it. Align the new wiper blade with the connector and slide it into place until it clicks or locks securely. Gently lower the wiper arm back onto the windshield, and repeat the process for the other wiper blade.

How do I reset the maintenance light in my Mercedes 240?

To reset the maintenance light in your Mercedes 240, start by turning the ignition key to position II, without starting the engine. Within four seconds, press and hold the "0" button on the instrument cluster until the maintenance indicator resets. Release the button and turn the ignition off. When you turn the ignition back on, the maintenance light should be reset. It is important to note that the specific steps may vary slightly depending on the model year and options of your Mercedes 240, so consulting the owner's manual is recommended.

How often should I have the brake pads replaced in my Mercedes 240?

The brake pads in your Mercedes 240 should be replaced approximately every 30,000 to 70,000 miles, depending on various factors such as driving style, road conditions, and the type of brake pads installed. It is important to regularly inspect the brake pads for wear and have them replaced if the thickness is below the manufacturer's recommended limit. Additionally, listen for any unusual noises, such as squealing or grinding, as these can indicate worn brake pads that require immediate attention.

How often should I replace the air filter in my Mercedes 240?

The air filter in your Mercedes 240 should be replaced approximately every 15,000 to 30,000 miles, or as indicated by your vehicle's maintenance schedule. However, it is recommended to visually inspect the air filter regularly to check for excessive dirt, debris, or damage. If the air filter appears dirty or clogged, it should be replaced sooner to prevent reduced air flow to the engine, which can negatively impact performance and fuel efficiency.

What should I do if the battery in my Mercedes 240 dies?

If the battery in your Mercedes 240 dies, the first step is to attempt a jump start using jumper cables and a functioning vehicle. Connect the positive (+) terminal of the dead battery to the positive terminal of the charged battery, then connect the negative (-) terminal of the charged battery to an unpainted metal surface on the dead vehicle. Start the charged vehicle and let it run for a few minutes to charge the dead battery. If the jump start is unsuccessful, it is recommended to have the battery tested and, if necessary, replaced by a professional technician.

What type of coolant should I use in my Mercedes 240?

In your Mercedes 240, it is recommended to use a high-quality, ethylene glycol-based coolant that meets the requirements of Mercedes-Benz. Look for a coolant that is free of silicates, nitrates, and phosphates, as these can be harmful to the engine. It is also important to choose a coolant with the correct mixture ratio of coolant to distilled water, typically a 50:50 ratio, to ensure optimal cooling and protection against freezing and overheating.

What type of engine oil should I use in my Mercedes 240?

It is recommended to use a high-quality synthetic engine oil with the correct viscosity and specification for your Mercedes 240. Consult your vehicle's owner's manual or the oil cap for the recommended oil type, such as 5W-30 or 0W-40, and look for oil that meets the specifications of Mercedes-Benz, such as MB 229.5 or MB 229.51. Using the proper oil will help ensure optimal engine performance, protection, and longevity.

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Chilton's repair & tune-up guide, Mercedes-Benz, 1974-79: Gasoline & diesel models, 230, 240D, 280, 280C, 280E, 280CE, 280S, 280SE, 300D, 300CD, 300SD, 300TD, 450SE, 450SEL, 450SEL 6.9, 450SL, 450SLC