If your car has a timing belt (not all cars do – some cars have timing chains), you need to know two things; the factory-recommended replacement interval, and when it was last replaced. If you have no record of replacement, or if you know that it’s overdue, you really should go ahead and replace it. A timing belt replacement may or may not be a DIY job. But, it never hurts to at least understand the process.

Your car’s timing belt controls the camshaft(s) rotation in relation to the crankshaft, which in turn opens the valves at the correct intervals, allowing your car to run properly. If your car has a non-interference engine, and the belt breaks while you’re driving, you’re going to need a tow, but you’re unlikely to otherwise damage the engine. On the other hand, a broken timing belt on an interference engine most likely will cause severe valve damage and may require a total rebuild of your engine. Even if you’re not doing the job yourself, it’s helpful to understand it. Although any one of the following steps may not apply to your car, it’s a good basic overview of the procedure.

In the case of longitudally-mounted engines, you’re likely going to need to remove your car’s radiator first in order to gain access to the timing covers. Next, you’re going to want to rotate the crankshaft, usually via the pulley bolt, to the point specified in the factory repair procedure for timing belt replacement. Next, you remove the crankshaft pulley and timing covers. From there, you verify that the crankshaft and camshaft(s) are properly lined up for timing belt replacement. In some cases, you’ll need to lock the camshaft(s) and crankshaft in place with special tools. Next, you loosen tension on the belt at the tensioner and remove the belt. While you’re in there, check the condition of the belt idlers. If they don’t spin silently, the bearings are wearing out and you need to replace the idlers.

Once everything is off, you can install the new idlers, then the belt and tensioner. Before you put the covers back on, double and triple check whether your camshaft(s) and crankshaft are still properly lined up for belt installation. You don’t want to start your car with a misaligned belt. If you have a non-interference engine, the car likely won’t start and you’ll need to do the job again. If your car has an interference engine, starting it with a misaligned timing belt can be as hazardous as a broken timing belt.

Also, pay attention to other items that may need to be replaced. If your water pump is driven off the timing belt, for example, this is an excellent opportunity to install a new one without incurring much additional labor. Once again, though, if timing belt replacement seems to complex, you may want to leave it to a mechanic until you’re more confident in your repair skills.