Timing Belt Replacement: purpose, construction, types, check, consequences of break

The combustion engine includes a mechanism that regulates moving gases– called the valve mechanism. The timing belt is the driving base of this mechanism and is an essential part that provides engine work.

When to replace

It`s the first that comes to mind when we think about engine maintenance and repair – when the timing belt is replaced.

Untimely replacement of the timing belt is one of the common reasons why the engine isfailed.This fact requires carefully following to manufactures recommendation on when to change the timing belt. The timing belt replacement intervals are usually between 70,000-90,000 miles.

Another good piece of advice, the first that you must to do after buying the mileage vehicle is timing belt change. Usually, such work is done together with technical fluids changing, like motor oil, transmission fluid, etc. The guide and parasitic rollers are changed in process of replacing the belt.

Why timing belt need

The main task of the timing belt is keeping mechanical timing between the crankshaft and the camshaft. In the working process, the timing belt transmits rotation moment from the crankshaft to the camshafts providing half the speed.  You can see in the picture where the timing belt is situated.

The timing belt transmits rotation moment from the crankshaft pulley to the camshaft pulley. Then the eccentrics located on the camshafts, by means of pushers, rocker arms, and rods, open or close the valves at strictly defined points in time, thus ensuring the movement of gases in the engine cylinders. The scheme of timing belt located which you have seen is the most widespread in modern engines.

What is timing belt made of

As rule, the timing belt is located toward the front of the motor under the timing cover. The timing belt is made with high-quality rubber and reinforced with nylon chords. Over years of operating, the rubber belt is degraded and destroyed; so you need to change the timing belt in time.

Timing belt Construction

The timing belt has teeth construction on the inside working surface. There are three forms of teeth:

  • Trapezoidal;
  • Rounded;
  • Complex.
Timing belt is broken

The rounded form is providing the needed loaded distribution by a surface that is done in this form better than the Trapezoidal. That is why the risk of jumping teeth is minimal. You should mean, that timing belts work in high temperatures diapason: the temperature of a belt can be over 80 degrees in the summer time.  

The structure of the timing belt has a multilayer base. The upper layer contains synthetic rubber compounds resistant to temperature extremes and wearing, and the inner layer involves a fiberglass cord that provides tear resistance. Beyond that, on the teeth, and in some cases on the outer surface of the belt a fabric braid is used.

What happens when the timing belt is broken

In the operating process, the timing belt loses its technical characteristic that leads to valve timing shift, engine difficulty to start, exhaust smoke (the result of incomplete combustion), engine vibration, and the appearance of extraneous noises.

Timing Belt Replacement Cost

Imagine that the timing belt is broken, what is being with the engine?  At this point, the valves are stopping, but the pistons continue moving. Accordingly, after a while, they are meeting.  The result of this meeting could be bent valves or piston damage.

Timing Belt Replacement Cost

Usually, a timing belt replacement includes changing all kit consisting of the belt itself, 2-3 idler pulleys, and a tensioner. Timing Belt Replacement will cost between $400 to $600.

Author: delfi

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