Perfect timing is a key to smooth and efficient engine operation. This means that all your intake and exhaust valves must close and open just at the right moment as well as every spark plug must create a spark when an air/fuel mixture is compressed and a specific piston reaches its top dead center. For this reason, every internal combustion engine is equipped with a timing belt or chain. It synchronizes movements of the crankshaft connected to the pistons with movements of the camshaft(s) driving the intake and exhaust valves.
By design, your timing belt is a rubber or synthetic toothed or ribbed belt reinforced for added strength and durability. It is attached to the crankshaft at the bottom of the engine block and to the camshaft(s) at the upper part of the motor. The crankshaft pulley drives the belt, which in turn, spins the camshaft pulley(s). Most likely, your timing belt also operates the water pump and the balance shaft.
A timing belt usually needs to be changed every 60000 to 100000 miles even if it seems to be in perfect condition. Trying to save some money by not replacing your timing belt according to the manufacturer’s recommended intervals may cost you a pretty penny when it suddenly fails, causing a lot of engine problems.
You should not confuse a timing belt with a timing chain. While both of them do the same job driving camshafts and other engine accessories, they are completely different due to the materials they are made from. A timing belt is made of rubber, which makes it quieter in operation than a timing chain. However, since the latter one is made of steel, it is more durable and lasts longer than a timing belt. Thanks to their superior strength and durability, timing chains had been installed on virtually all vehicles produced till the 1980s. Today, both timing chains and timing belts can be found in modern vehicles.
A faulty or worn-out timing belt can cause a number of engine troubles, which may cost you an arm and a leg. That’s why you should be aware of the symptoms of a bad timing belt.
Signs of a bad timing belt:
Lack of engine performance
Under normal conditions your timing belt keeps the valves and pistons perfectly synchronized. If the belt wears out, it can slip and make them out of proper alignment. As a result, the valves can open and close at the wrong times, causing backfires or misfires, which are synonymous with poor engine performance.
The check engine light is on
Your engine control unit monitors most aspects of engine operation. If it detects any problems caused by a bad timing belt, it will turn on the check engine light.
Ticking sound from the engine
A faulty timing belt can cause your engine to run poorly. A ticking sound can be one of the consequences of an improperly running engine.
You can’t start the engine
If your timing belt breaks, your engine won’t start since its intake and exhaust valves will not open to enter an air/fuel mixture into the cylinders. If the belt breaks when the engine is running, this may cause severe damage to the valves and pistons.
Low oil pressure
A slipping timing belt can cause physical damage to the camshafts, so their small pieces will end up in the oil pan and block the flow of oil to the engine.
A timing belt that slips or runs out of alignment can cause loose nuts and bolts as well as damage to the gasket between the timing belt cover and the engine.
How to fix a bad timing belt
If you notice signs of a bad timing belt, your first step is to remove the timing belt cover and visually inspect the timing belt for damage. If the teeth on your belt are worn out, sheared off or hollowed out, your timing belt should be replaced. The other signs of a bad timing belt are worn-out edges, cracks on the rear side and oil marks.
A timing belt should be replaced by a professional as this often involves removing several engine accessories. If there is oil on the belt or in the timing belt area, the source of oil leaks must be found and fixed before installing a new belt. Besides, it is always a good idea to check and replace your pulleys, tensioners, water pump and other related parts that may also have signs of wear.
Reassembling a timing belt requires proper alignment of all engine parts, including the crankshaft and the camshafts. On many vehicles, you’ll find special timing marks made to help you out with that.