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Mason Shields, October 8 2019

Timing belts and what makes them spin


What do timing belts do?

Timing belts are there to spin the internal components of the engine.  The belt goes around the crankshaft and the camshafts and allows everything to spin in sync.

On many cars, the timing belt also spins the water pump allowing it to circulate the coolant. 

What happens should the belt break?

What will happen all depends on what type of car you have. All cars will stop running since the motor will not be able to spin over.  Now some engines are what are called “interference engines.”  In an interference engine, the valves have enough clearance that they can drop below the level of the head and hit the pistons.  The timing belt is what keeps everything in time so nothing will hit. 

If an engine is an interference engine and the timing belt should break then you run an excellent chance of the valves hitting the pistons and damaging the valves.  The pistons can also be damaged though that is not as likely to happen.  The rule of thumb is if the timing belt breaks on an interference engine then the cylinder head will need to be removed for the valves to be replaced. 

If an engine is not an interference engine, then the car will of course not run, but no damage will occur.  After replacing the timing belt, the engine should start and run fine.

What else could go wrong with the timing belt?

A timing belt can go bad without breaking.  As the belt gets old, the rubber can get weak in the belt allowing it to stretch.  If the belt stretches, then it can allow the engine to get off time.  If the engine is off time, then the valves will not open and close at the correct time causing the engine not to run right.  That would create a lack of power and possible engine miss fire. 

Whats all involved in replacing the timing belt?

When its time to replace the timing belt it's always a good idea to get whats called a “timing belt kit.”  The kit comes with the timing belt but also all the timing belt pulleys, tensioner, and water pump if needed.    We also recommend replacing all items at the same time so that you don’t run the risk of something going bad and having to redo all the work again. 

When should you replace the belt?

The best guidelines for when to replace the timing belt is to go by the manufactures guidelines.  Those can range from replacing the belt every 60000 miles to every 120000 miles.  You do also want to factor age too in case the mileage is not driven.  A good rule of thumb, though this can change based on where you live, is the life of the belt is about ten years.  Where you live can affect the life of the belt based on the weather.  An area that’s hot and dry will cause the rubber to dry out faster than an area that’s cold and damp.   A good indication of what shape the timing belt is in would be the external belts.  If the outer belts are cracking, then it’s a good bet the timing belt is cracking also. 

What if your car does not have a timing belt.

If your car does not have a timing belt then it has a chain.  The principle is the same but there is a whole lot more involved with a timing chain.  The main thing to remember on a chain is it is lubricated by oil.  If the oil level gets low or the oil gets old and starts to break down then damage will be done to the chain.  should a chain break or get enough slack in it you will suffer engine damage.

Written by

Mason Shields

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