COVER-SPRING 7M1345 - Caterpillar

deposits can accumulate in the combustion chambers of engines that use gas with a low BTU such as bio-gas fuel, and landfill gas. The deposits can affect the characteristics of combustion. Erratic operation can result. The rate of recession of the exhaust valves can increase. The risk of guttering of the exhaust valves can increase.Note: Use of a platform may be necessary to inspect the combustion chamber.Use a borescope to inspect the combustion chamber. The inspection will provide information about the internal condition of the engine.A borescope with a lens that can be rotated is recommended. This type of borescope provides a clear view of the combustion chamber and of the bottom deck of the cylinder head. Photographic documentation or video documentation is also recommended. Consult your Cat dealer for information on available borescopes.When possible, insert the borescope through the opening in the cylinder head for the prechamber assembly and the ignition body. This location will provide the best possible view of the entire combustion chamber. This procedure requires draining the coolant to a level below the cylinder head. If draining the coolant is not possible, insert the borescope through the opening for the combustion sensor. Look for the following conditions:
Valve wear
Deposits on the valve seat
Deposits on the valve face
Polishing of the cylinder walls
Scratching of the cylinder walls
Deposits on the cylinder walls that are above the upper limit of the piston strokeDeposits that are on the valve face and the valve seat can cause guttering of the valve. Inspect the valve seat and the valve face for excessive deposits. If excessive deposits are found, replace the valve and the valve seat.Determine whether the exhaust valve face has erosion from pitting. This procedure requires the exhaust valve to be in the open position. To obtain as much detail as possible, obtain a close up view of the valve face. Erosion of the exhaust valve face can lead to guttering of the valve. If erosion is found on the exhaust valve face, recondition the cylinder head as soon as possible.Note: Operation at loads less than 50 percent of the rated load can result in an excessive buildup of carbon deposits in the combustion chamber. The deposits can lead to detonation and premature ignition. This condition is more obvious at certain engine speeds and loads.