Mercedes-Benz W123 (1976–1986, sedan, estate and coupe): common faults, maintenance guides and repair tips.
The most common causes are a worn driveshaft centre support bearing and its rubber, a broken vibration damper, worn flex discs (rubber joints) and poo...
1. Drain the rear axle oils, remove the wheel and the brake caliper (the brake hose does not need to be opened). 2. Detach the shaft from the hub and ...
The play is adjusted with the hex socket screw and its locknut on top of the steering box, in small steps of at most a quarter turn, with a test drive...
Worn control arm bushings (rubber bushes) let the arm move, which is heard as rattling or creaking. The rubber bushings of the mounting are available ...
1. Remove the brake pads and try to press the piston in with a clamp. 2. If the piston does not move, remove the caliper and push the piston out. 3. C...
1. Fill the brake fluid reservoir to the brim and keep it full the whole time. 2. Start from the wheel with the longest brake line (right rear wheel) ...
The front disc diameter is 278 mm. The thickness of a new rear disc is 10 mm (model years 1976–85) and the recommended minimum thickness is 8.3 mm. Br...
Common causes are stuck contacts in the flasher relay, poor earthing of the rear lights, and wrong wiring or moisture in the connections of the towbar...
The most common cause is a worn fuse: the ends of the fuse have corroded even though the fuse looks intact from the outside. Braking and the turn sign...
Measure the voltage with the engine running and the lights on: about 14 V is fine, below 13 V points to a charging fault. First check the earths: from...
The cause is usually worn brushes or a faulty solenoid (the starter motor's engagement relay). Poor connections at the battery terminals or the wires ...
The diesel's shut-off lever is moved by vacuum. If the shut-off diaphragm leaks or a vacuum hose is detached, the lever does not move and the engine k...
The W123 central locking runs on vacuum, so an electrical fault does not usually explain it. The cause is almost always a leak in a vacuum hose, in th...
Usually the master cylinder or the slave cylinder is leaking and air has got into the system. The slave cylinder is on the side of the gearbox on the ...
Use ATF transmission fluid that meets Mercedes requirements. The total capacity is about 6 litres, and about five litres come out at an oil change. Th...
Kickdown is electric: there is a switch under the accelerator pedal and a solenoid on the side of the automatic transmission. The shift point and the ...
The cause is usually the thermostat, air left in the system, a clogged radiator, a poor expansion tank cap or a weak water pump. Removing the thermost...
The W123 gauge is mechanical, and its scale ends at about three bar. As a guideline, on a warm engine the pressure should be at least 0.3 bar at idle ...
Disconnect the plugs' wiring so that the plug being measured is the only one connected. With the multimeter's continuity beep function, put one probe ...
1. Remove the drive shaft. 2. Undo the clamping nut counterclockwise with a special wrench. The nut is very tight, and you can make the wrench yoursel...
1. Remove the interior trim and plastic pieces and the rear window heater wires. 2. Remove the old seal starting from the middle with a screwdriver or...
Often the fault is in the pump relay: its internal solder joint may be burnt or melted open. The relay is in front of the fuse box cover inside a tall...
The rear axle takes hypoid oil of class GL-5 and viscosity 85W-90. Multigrade 10W/30 oil does not meet the requirements. The manual gearbox takes ATF ...