The C-15 is the model number for the 3406E, which is a heavy-duty diesel engine manufactured by Caterpillar. The 3406E, which is a stock engine in front loaders and other heavy Caterpillar vehicles, has a four-stroke, 4.614-liter engine. Adjusting the valves on the 3046E C-15 is part of regular engine maintenance. The valve adjustment should be performed when the engine is cold so that when the engine gets hot and the adjusters expand, they don't keep the valves open.
Open the engine compartment lid on the Caterpillar.
Remove the valve cover retaining bolts with the socket set and lift the valve cover up and off.
Remove the spring, diaphragm, gasket and inner sleeve from the valve housing. Separate and clean all of the parts completely with a clean rag and spray engine cleaner.
Apply gasket cement to the inside of the diaphragm and then re-assemble it along with the spring, gasket and inner sleeve. Twist the inner sleeve slightly to the right, so that it fits snugly, to adjust it.
Slip the valve cover back into position, insert the retaining screws and tighten them with the socket set. Close the engine compartment cover.