How to prevent and diagnose timing belt tracking


Every technician knows that timing belt tracking is a serious business. In the worst-case scenario, it can cause premature timing belt failure, or cause trouble (and costs) even before that. Let’s backtrack a little and discuss the importance of preventing belt tracking, review possible causes, and give some troubleshooting tips. 

Why it’s crucial that the timing belt is correctly aligned

A timing belt that runs off the pulleys, even just partly, is bound to rub against other components. If it grinds against the timing cover, this plastic lid will start to melt. Contact with any other part will cause belt abrasion: the edges fray and the belt becomes increasingly narrower. The speed at which this happens, depends, firstly, on the amount of tracking and, secondly, on the material of those parts the timing belt is rubbing against. In another scenario, the timing belt can even be cut through lengthwise, obviously causing the engine to grind to a halt.

The tracking can also be so bad that, in combination with the wrong tension (either too high or too low), it can cause both the timing belt and the tensioner’s or pulley’s metal running surface to overheat and fail. 

Possible causes of belt tracking

In most cases, belt tracking can be traced back to misalignment. Worn engine parts, like a ball bearing that has seen better days and that misaligns the water pump or the tensioner for instance, or a worn mounting part, can cause an alignment problem over time. In other words: timeworn parts start a chain reaction that stresses other parts – sometimes with severe (and expensive) consequences. 

In some engines, improper belt tension can cause belt tracking problems. And, lastly, if a car has been involved in an accident, the fact that the timing belt is hidden means that the damage may go unnoticed until it’s too late.  

Troubleshooting: who’s to blame? 

If the timing belt is shiny or glossy on one side – in other words, if it’s glazed – you can be sure of a tracking issue. Yet determining what causes it, is not so easy. The two main types of timing belt misalignment are parallel (the driver and driven shafts are parallel, but the driver and driven timing belt pulleys on these shafts lie in different planes) and angular misalignment (the driver and driven shafts are not parallel).

A simple trick to check both parallel and angular misalignment is by using a piece of cordage or a ruler to check alignment (as shown in the drawing above).