Like all belts on your car, the timing belt is subject to wear and tear. It is best to defer to your owner’s manual for recommended replacement intervals (generally somewhere between 50,000 – 80,000 miles, may vary depending on make and model).

How the timing belt system works:

The timing belt is a toothed belt that keeps your engine synchronized (in time). It ensures that the camshaft and crankshaft are in synch during operation, and that the valves open and close at the right times in relation to piston movement. As such, it is perhaps the single most important maintenance item on your car and should be replaced at the manufacturer’s recommended service interval.

To sum this up in a nutshell, the piston and valves in your engine essentially take up the same space. Obviously, they can’t do this at the same time, or they’d crash into each other and cause serious damage. The timing belt ensures that their movement is timed correctly. When the belt breaks, timing is thrown off. The most common outcome here is bent valves (due to impact with the piston), but it can also cause damage to the cylinder head, or even to the camshaft itself.

Common reasons for this to happen:

  • Failing Water Pump Pulley: The most common cause of squealing or squeaking from the timing belt cover is the water pump pulley. If the bearings in the pulley are beginning to fail, they will make noise. Eventually, they’ll seize and the water pump will no longer operate, causing your engine to overheat.
  • Serpentine or V-Belt Slipping: Another common cause here is noise transference from a slipping serpentine or V-belt. In these instances, the sound is actually coming from the belt slipping on a pulley and it just SOUNDS like it’s coming from behind the timing belt cover.
  • Belt Too Tight: Again, the sound cannot be coming from your timing belt, but if you’ve recently had your serpentine belt or V-belt replaced, it could be adjusted too tight, which will cause squeaking or squealing.

How important is this service?

If you’re hearing a squealing or squeaking sound from behind the timing belt cover, chances are good that it’s the water pump pulley. If this pulley fails, your engine will overheat, causing potentially devastating damage (up to and including a cracked block). The best defense here is to ensure that the water pump is changed when the timing belt is changed, and to always follow the automaker’s service recommendations. One of Sierra Car Care’s professional ASE Certified auto mechanics can listen to and inspect your engine, diagnose the problem and then repair it.