1983 300SD OM 617.951 Valve Adjustment |
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| Make a note of the various connections to the items mounted on the valve cover before beginning. |  |
| The importance of the Hazet special wrenches (3) for the valve adjustment procedure became immediately obvious during the adjustment of the first valve. The long wrench in the middle is not related to valve adjustment. It is a 13mm/14mm combination wrench for changing the gear oil in the rear gearbox (differential). |  |
| Disconnect the vacuum connection on the top of the valve cover, the throttle linkages, breather tube from the valve cover to the air filter housing and the fuel return line between cylinders 3 and 4. |  |
| I chose to remove the air cleaner housing to facilitate access to the valve cover. This also gives me an opportunity to look for any other possible problems that may have otherwise been obscured from view. This view shows the layout of the intake and exhaust side of the OM617.951 engine. |  |
| The cam assembly from the front. |  |
| From the left (US driver's) side. |  |
| Cam Orientation. You want to orient the cam such that the lobe is directly opposite the contact area of the rocker. The cam surface is not round at areas other than the main lobe, so orientation matters. The feeler guage will be used from the direction indicated by the arrow. The guage should have a light resistance fit between the cam surface and the rocker surface. There is no secret to the order in which the valves are adjusted. I started from the front and worked toward the rear of the engine. Make sure you know if you are working with an intake or an exhaust valve and use the correct feeler guage accordingly. A port diagram close at hand is a good idea if you are not really familiar with the engine. |
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| This is the port diagram for the OM617.951 in my 1983 300SD. Make sure you are using the correct port diagram for your machine. |  |
| Valve adjustment tools on the intake valve of #1 cylinder. Even with these tools, I
found the #5 exhaust valve to be somewhat of a challenge due to the sound proofing wall
just behind the engine. I ended up using a 14mm combination wrench to complete that
valve. For this particular model, with the engine cold, valve clearances are restored to 0.40mm on the exhaust valves and 0.15mm on the intake valves. Check the MB literature for the proper valve clearances for your model. I used a remote start switch tool to "bump" the engine into cam position for valve adjustment. |
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| With the valves adjusted and a new valve cover gasket, she is buttoned back up and ready for another 15,000 miles of service. |  |
| Note, I could not resist the temptation to hit the valve cover with some Mothers aluminum polish while the cover was off and readily accessible. |  |
