CYLINDER GP-HOIST 9T2807 - Caterpillar

Series EnginesWhen service work is performed in the cylinder head area, check for the 4D514 Plug. See the illustration.
The 4D514 Plug must be in place in the cylinder heads when the engine uses dry exhaust manifolds. In this applications the plug prevents coolant leakage between the cylinder heads and the exhaust manifold.
The 4D514 Plug must not be used when the engine has water cooled exhaust manifolds. If the plug is used in this application, it will block some of the coolant flow from the cylinder head to the exhaust manifold. Overheating damage to the exhaust manifold can be the result. The passage, when the plug is removed, also helps to completely drain coolant from the manifold when the cooling system is drained. This helps prevent freeze damage.
Make a note of this information in the Parts Books for these engines.
4D514 Plug Location