Checking and adjusting clearances in the valve drive mechanism on M123 and M110 engines (Mercedes-Benz E-Class W123)

Valve clearances can be checked and adjusted on both a hot and cold engine.

Exhaust valves

Intake valves

Valve arrangement:

A - engine M123
B - M110 engine

Adjusting valve clearances on the M 123 engine

Article was borrowed from the website [MERCEDESMAN]

1. Remove the cylinder head cover and unscrew the spark plugs.

2. Rotate the crankshaft pulley to set the piston of the first cylinder to TDC so that the inlet valve is closed (the top of the cam lobe is directed upwards).

3. With a set of feeler gauges (see table) check the clearance between the cam back and the lever back. If the clearance is normal, the feeler gauge should enter with a slight pinch. If not, loosen the lock nut and turn the adjusting bolt with a wrench to achieve the proper clearance. After adjustment, tighten the bolt lock nut.

4. If the adjusting bolt fails to provide the required clearance, the push head on the valve stem can be replaced.

5. Repeat this operation on the remaining intake valves in the sequence 1-5-3-6-2-4; then adjust the exhaust valves in the same way.

6. Pay special attention to the location of the valves.