Ignoring your timing belt can come with a high cost. Timing belts don’t often snap, but when they do, it can cause piston damage, ruined cylinder heads, and engine valve damage.

Probably, when you think of your engine, you picture the valves and pistons, but you don’t think much about what keeps them in good working order. Let’s state it plainly – nothing is more important than the timing belt. It drives the camshaft, which is what keeps the valves synchronized, and the crankshaft, which controls the pistons. Your timing belt tells the pistons when to rise and fall, and the valves when to open and close.

How to tell if your timing belt is bad

Timing belts don’t often give you a lot of warning when they’re about to give way – they might squeak or chirp, or they might just suddenly break. More often, though, damage is due to wear in the timing belt. You can do a visual check – see if there’s any cracking, glazing, missing teeth or oil contamination. Or you can have a mechanic check the belt for you. Most vehicle manufacturers also recommend that you make timing belt replacement a part of your routine maintenance, replacing it every 60,000 miles. Some belts are good for up to 100,000 miles. If you’re in doubt, check your owner’s manual, or ask your dealer or mechanic.

Interference vs. non-interference engines

The level of damage caused by a broken timing belt can depend on the type of engine you have in your car. A non-interference engine provides clearance between the valves and pistons, so if the timing belt breaks, you might end up with bent valves, and you might have to have your cylinder heads rebuilt, but the engine isn’t likely to be destroyed.

With an interference engine, though (and about 70% of the vehicles on the road today have this type of engine), the pistons and the valves move within the cylinder – just not at the same time. The pistons and the valves “own” the cylinder at different times. Here’s the thing, though – the period of time between “ownership” can be less than a second. If the timing is off, be it less than a second, there is nothing to stop the pistons and cylinders from colliding. This throws the rods off, and they start to poke holes in the engine block. Eventually, the engine simply cracks in half, and there’s no way to repair it.

Now you know the disastrous consequences of neglecting your timing belt – engine valve and piston damage, bent valves, cylinder heads that need to be rebuilt or replaced, and possibly even total engine destruction. If you don’t want to see those dollar signs adding up, check your timing belt regularly, and have your mechanic replace it on schedule.

This article originally appeared on YourMechanic.com as Bent Valves and Other Common Issues After a Timing Belt Snaps and was authored by Valerie Johnston.


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