The E36 is the third generation of the BMW 3 Series, and one of the entry-level offerings from the this Bavarian manufacturer. The E36 uses a timing chain to control the timing of the camshafts and the valve train.
The timing chain on an E36 is fastened to the camshaft with sprockets. using a timing chain is a much more durable method of ensuring the timing on the engine than using a timing belt. A timing belt is a pliable belt that needs to be replaced periodically.
The timing chains that E36s use are generally considered reliable for the life of the engine, so it most likely will never need to be replaced. However, any mechanical part can fail. If the engine in question has very high miles (250,000 or more), it may be prudent to replace the timing chain as preventive maintenance.
Though the timing chain itself may never need to be replaced, the tensioner that is responsible for keeping the chain tight when the engine is running may need to be replaced. The tensioner can be responsible for a noisy timing chain and replacing it will usually solve any noise problems