Technical – N42 Timing Chains

N42 Timing Chains

(318i E46 and 318ti – facelift engines)

This model of BMW was quite popular when it came out post 2001. It was pretty advance for its time however it had its chink in the armour which could be quite costly to repair. Read on don’t despair just yet.

There is preventative maintenance that is cheap but in missing out on it, it could lead to a big bill.
The weak point falls on the Timing Chain Tensioner and after a bit of wear & tear they stop working. This part has been modified and redesigned by BMW. The new ones are a bit longer (see pic below). This niggle could be enhanced by using the wrong oil or TOO LONG SERVICE INTERVALS

A mechanic would be able to tell you if it has been replaced; the new tensioner has a bigger head. 
Having the old tensioner fitted you run the risk of having the chain jump one tooth at a time causing the exhaust cam timing to be incorrect. 
The position plate on the cam moves incorrectly causing electrical faults to occur as the camshaft sensor does not function properly. This can lead to the top and bottom chain guide rail plastics also breaking and falling into the sump. (See pic below of Guide rail) To replace the guides is expensive as it is not a straightforward job. We recommend that when you sort out the oil leak problems these cars are prone to – have the tensioner replaced as well. 
For more on these engines lookout for the upcoming “Oil leaks and Oil consumption article”