BMW 18407521826 Exchange Exhaust Manifold With Catalyst

Remove the engine cover and support the engine from above with a suitable hoist using a tow hook (BMW#72158108670) to support the N52 engine at the front of the cylinder head. Working from under the engine, remove the front end reinforcement plate and the complete exhaust system. Remove the ground cable from the body and evacuate and recover the A/C system for the N52 engine by removing screws, disconnecting the electrical connection, and disconnecting the pressure and suction A/C lines. Remove the oxygen sensors. For the M54 engine, remove the right engine support mount by taking out the fastener for the isolator and the bolts between the mount and engine block, then set the mount aside. For the N52 engine, follow the same procedure for the right engine support mount. To remove the exhaust manifold for cylinders 4-6, take out the fasteners and remove the manifold, ensuring that during installation, the process is reversed, sealing surfaces of the manifold and cylinder head are cleaned, new gaskets and hardware are used, and the exhaust system is checked for leaks.

Remove the exhaust manifold for cylinders 1-3 and the oxygen sensors. For the M54 engine, also remove the secondary air pump. Take out the fasteners from the rear exhaust manifold and then remove the manifold. During installation, which is the reverse of removal, ensure to clean the sealing surfaces of the manifold and cylinder head, use new gaskets and hardware, and check the exhaust system for leaks.

Pre- and post-catalyst oxygen sensors are mounted in each exhaust manifold.