Valve adjustment on M116 & 117 Engines

[William]

My question pertains to Mercedes engines M116 and 117 and using the “go-no go” gauge in establishing the unloaded “basic position” of the “hydraulic lash compensator” (HLC) a.k.a. as the “hydraulic ball stud assembly".

As experienced by those who have replaced “rocker arms” on these engines, when using the “go-no go” gauge, the “Mercedes Service Manual CD” advises to install the appropriate size “thrust/shim pieces” (a.k.a. as hockey pucks) so that the measuring edge is in the center of the “1.2 mm red measuring groove”. This is the “ideal” basic position of the hydraulic lash compensator.

In practice, however, this “ideal basic position” cannot always be achieved. There are those instances, for example, where the insertion of a 5.1 mm thrust piece causes the “measuring groove”to ride a bit LOWER than ideal (calling for a thinner, 4.75 mm, thrust piece). Then, when the thinner thrust piece is inserted it makes the “red measuring groove” ride a bit HIGHER than ideal. In both cases, the low and high deviations from the ideal position are near equal in magnitude.

When you have the situation described above, what is the best approach: “Is it best to opt for the thicker thrust piece....... or use the thinner thrust piece..........or does it really matter?”

Thank you for responding.

[BDBENZ]

I am going through and checking valve adjustments and have the same question as William in his post. I could use some guidance.

Thanks.

[mbdoc]

The adjustment process isn't that easy & many times you will get a FALSE reading. BEFORE you try to make any adjustment allow the cam lobe on the incorrectly adjusted valve completely depress that rocker for 45-60 seconds. Then put the TOOL over the rocker & look at the groove on the go-no part of the shaft. IF you are still off then get the next smaller(or larger) shim & DO that same process with the cam lobe holding the valve open & the lifter compressed...then you should see a change in position.