A rebuilt engine involves removing the engine from the vehicle and completely disassembling it. Once the engine has been disassembled, cleaned, and inspected, all damaged parts are replaced with new or refurbished replacement parts. All new gaskets, seals, and lubricants are used in the assembly of the rebuilt engine that will meet BMW OEM standards. The most common components to be replaced include bearings, gaskets, seals, timing belt or chain, valve springs, and the oil pump. Major parts are replaced only if they are needed, and often include camshafts, crankshafts, and pistons. In the most severe cases, we will have to machine parts that have been warped. The Advantages of Rebuilding an engine is the connectivity and compatibility with the existing ECU and electrical system. The ECU is programmed to communicate with the engine originally installed in the vehicle. When a new engine is installed the ECU may have problems connecting and communicating with the new engine. When the engine has problems communicating to the vehicle it will require either a reprogramming of the ECU or replacement.