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What is a Timing Belt and does it need to change?

timing belt
timing belt

Posted on Sunday, January 7, 2018
By: Dave's Auto Service
Categories: Kia  |  Buick  |  pontiac  |  coolant  |  chevrolet  |  ford  |  chrysler  |  dodge  |  honda  |  subaru  |  toyota  |  mazda


When we tell a customer that their car engine has a Timing Belt , their response is what is a timing belt and why do I have to change it?

What the timing belt is a rubber type toothed belt. And its job is to keep the moving parts inside the engine in sync, or as some mechanics call it, in time. Think of the engine essentially as 2 half's, an upper half and a lower half.

The lower part of the engine holds the crankshaft. The crankshaft is a rotating assembly. The pistons and connecting rods are attach to the crankshaft.

When the spark plug fires the fuel and air mixture in the cylinder, the pistons are pushed downward causing the crankshaft to spin. The crankshaft has a toothed gear attach onto the front. It is this gear that the timing belt rides on. When the crankshaft spins, this causes the belt to move and spin the upper half of the engine. Its the upper half that  contains the camshaft, or as some engines, multiple camshafts. The camshafts also have toothed gear attached to them also. The timing belt also rides on these toothed gears. When the camshaft spins, it pushes the valves open. This lets the air and fuel mixture into the cylinder by the intake valve. When the spark plug fires the air and fuel mixture, the burned gases and also lets burned go's out through the exhaust valve. And it's this burned gases that exits out your exhaust tailpipe. Now, as you can imagine, all of those moving parts inside the engine must occur at the correct " Time "

The belt, as stated before, is manufacture out of a rubber type of material. As it ages, the belt can loses its flexibility, and this can also cause the teeth to start cracking on the inside.  If the teeth are cracking bad, they can shear off or “break”. If this  break in the belt happens, it will allow the lower half of the engine to spin, but what also happens is the upper half of the engine stops spinning.

Then what happens is there are more than likely a couple valves are still open. As the crankshaft is spinning inside the engine, it will still push the piston upward. When the piston comes up, and most engines are a  interference engine, the piston will hit the valves that are still open. And when this happens, it will bend the valves. This most times is engine failure and will require the engine to be disassembly. Replacing the timing belt is a lot less costly service. The timing belt replacement can and will help prevent engine repairs from being needed

The timing belt also in most engines drives the water pump, it is a good idea to replace the water pump at the same time.  Also, there is a tensioner and idler pulleys that should be change as well.

I hope this helps you have a better understanding of the importance of changing your timing belt in your cars engine.

Tagged:timing belts, car repairs, auto repair, car repair, auto repairs

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