Some domestic cars and many import models have motors that require periodic valve adjustments. If the valve clearances are excessive, you will hear an annoying tapping and clattering under the hood of your car. Clearances that are too narrow are even worse, since tight valves will be quiet, but they will also burn out prematurely.
Many valve adjustments that you pay for are never really done. Often, mechanics are so brazen in the way they chisel their customers that they don’t even bother to remove the valve cover, which is a necessary preliminary step to reach the adjustment mechanism.
If you are suspect of the honesty of any shop you do business with, you can put a mark on a fastener on the valve cover to make sure that a mechanic at least went through the motions of removing the cover.
Put a small dab of paint of colored nail polish on one of the nuts or bolts that fasten the valve cover to the cylinder head. The paint must touch the nut or bolt and a portion of the valve cover itself. Pick an inconspicuous location and make the dab of paint or polish very small so as not to advertise your actions.
After they say the work is done, if the paint or polish has not been disturbed, you know that the cover was not even removed…so the valve adjustment could not have been done.
In that case, demand your money back and find another shop…an honest one hopefully.
