This injector sealing washer sits between the injector body and the cylinder head in the host engine. It compresses under the injector clamp load to form a gas-tight seal that prevents combustion gases from escaping past the injector and keeps high-pressure fuel from leaking into the cooling jacket or oil system. A worn or re-used washer allows blow-by, which causes a loss of compression and a visible soot deposit around the injector bore. The washer is manufactured by AGCO to match the original crush profile and material hardness, so it deforms to the correct thickness under the specified torque without over-compressing or splitting. On reinstall, always fit a new washer and discard the used one; the washer is a single-use crush component and cannot reseal after its first compression cycle.