How To: Mercedes-Benz Diesel Valve Adjustment

Mercedes-Benz Diesel Valve Adjustment Instructions

OM615, OM616 & OM617

The Importance of a Valve Adjustment

Mercedes-Benz recommends the valve adjustment to be done every 12,000 miles. Many old Mercedes have not had valve adjustments and are badly due for one. The job is very easy and with proper tools can be done by any beginner. Adjusting the valves will bring back your peak performance and fuel economy.

Why it's important to adjust your valves:
1.It ensures your engine is running at peak performance
2.It maintains fuel economy
3.It prevents expensive repairs down the road

Parts Needed:

  • 2 Bent 14mm Valve Adjustment Wrenches
  • 1 Feeler gauge(32 Blades)
  • 1 New Valve Cover Gasket(OEM or Elring)
  • 1 Valve Spring Holder Tool(Optional But Helpful) 

How To:

  1. Valve adjustments are to be done with a completely cold engine. Waiting overnight is best. 
  2. Remove the clamp and detach breather hose from the valve cover
  3. Take some pictures then remove any throttle linkage. Try to remove the least amount of linkage as you can. Flat head screw drivers works great.
  4. Remove all 4 of the 13mm valve cover nuts and lift the cover up and off.
  5. You can turn the engine by using the power steering pump or crank bolt. *ONLY CLOCKWISE* When looking at the engine from the front of the car.
  6. Power Steering nut is 22mm and requires a properly tightened belt to work.
  7. The crank bolt can be reached with a long breaker bar and 27mm socket.
  8. You can also use the bump starter method but i prefer hand tools. 
  9. Start with the #1 cylinder and point the lobe straight up
  10. You can tell which is Exhaust or Intake by looking at the manifolds.
  11. Print the Chart  at the bottom of the page and use it to keep track of your progress. The 4 Cylinder uses the same chart but 1 less valve to adjust.
  12.  All the NON turbo 4cyl and 5cyl diesels use (.10mm or .004 inches)  intake  and (.30mm or .012 inches)  exhaust.  The turbo models use (.10mm  or .004 inches) intake and (.35mm or .014 inches) exhaust.
  13. Check the valve with feeler gauge between the rocker arm and lobe. Set to have a slight resistance. 
  14. There are two nuts for adjusting. A top nut and a lower nut. 
  15. Loosen the 2 nuts and you can start adjusting.
  16. You can turn the top not clockwise to increase the clearance or counter clockwise to decrease it. Check with your feeler gauge.
  17. If clearance is set properly re-tighten the 2 nuts. Recheck clearance and adjust if needed.
  18. After all valves are adjusted install a new valve cover gasket
  19. Re-grease all throttle linkage fittings. 
  20. Tighten valve cover and breather hose

Test drive your vehicle to make sure everything is working properly
Valve adjustments are important maintenance tasks that should not be ignored. By following the steps above, you can easily do this job yourself and save money in the process. However, if you don't feel comfortable working on your engine, you can always take it to a mechanic and have them do it for you. 

Valve Adjustment Chart: