- home
- Technical part
- …
There are a lot of questions about the timing belt. The first most popular is - it’s torn, what to do, what the consequences may be. Where to run? Khan's engine? Mostly novice motorists write when the car gets stuck and doesn’t move anywhere. It is impossible to start it, and often this is not recommended at all in case of a break; in general, the driver panics. Today I will try to describe the action plan - both diagnosing and eliminating this malfunction. And you know, sometimes you can run into a decent repair! So read and delve into...
I hope there is no need to explain - what is a timing belt? Well, well - in short, it connects the engine shafts - the crankshaft and the camshaft in a certain sequence - so that when the pistons move up or down, only the necessary valves open or close. This creates the pressure inside the cylinders necessary to ignite the fuel mixture. Without a belt, the engine would not work - this is a fact, this is a very important link in the structure of the engine. Now let's talk about why there might be a break.
Why does the timing belt break?
Causes of product damage:
- low quality belt;
- errors made during installation or replacement;
- failure of the tensioner rollers;
- wear of the belt teeth (the teeth wear out constantly during the operation of the car);
- pump jamming;
- foreign objects entering the gas distribution mechanism.
Late replacement
The service life of modern new products for distribution mechanisms depends on the make of the car and is about 150 thousand kilometers (on older cars this figure is lower - about 70 - 100 thousand / km). If the vehicle is used in low temperature conditions, the service life of the belt is reduced to 60-100 thousand/km. In any case, experts recommend diagnosing the condition of the timing belt at least every 15 thousand kilometers.
Quality of spare parts
Quality determines the correct ignition of the air-fuel mixture, which affects the efficiency of the power unit. Installing and using cheap products in the machine can cause low drive tension, which will result in the belt quickly bursting.
Incorrect belt replacement
Errors made when installing the timing belt lead to asynchronous opening and closing of the valves, resulting in reduced engine power. The cause is usually too loose or too high a tension on the shafts. If the replacement of the product was carried out with errors, it may break after 1-2 thousand kilometers.
Characteristic signs of incorrect replacement:
- the product slides to the side;
- cracks have appeared or become noticeable on its surface;
- An unusual sound is heard when the engine is running.
Broken tension rollers
Tensioner rollers are designed to tension the belt on the engine shafts, so that it does not jump off while the engine is running. If the tension is weak, the strap will begin to slip, which will cause an increase in temperature and rapid wear of the auxiliary units. If the tension is excessive, the product can quickly burst, and a characteristic symptom will be a sharp sound from under the hood.
Destruction of timing belt teeth
With serious wear, the rubber teeth located in mesh with the shaft gears break off. With such a problem, the engine may not start, although the belt itself appears to be intact. The operation of the power unit as a result of tooth destruction is disrupted, as this leads to a failure of the ignition system.
Pump wedge
If the pump is jammed, it may not respond to turning, which leads to strong tension and breaking of the belt while the vehicle is moving. This problem is more relevant for domestic vehicles.
Foreign elements
If foreign elements get into the distribution mechanism (this could be dirt, small stones, engine oil), the camshaft or crankshaft may jam. To avoid this problem, it is necessary to periodically check the protective cover and fastenings.
Video: causes of timing belt damage
In the video, user Igor Belov spoke in detail about why the timing belt breaks.
Replacement
If the timing belt breaks (whether it’s a VAZ or a foreign car, it doesn’t matter), the first step is to install a new element. There are two reasons for the impending replacement:
- Natural wear and tear. Manufacturers recommend replacing the element at least once every 80 thousand kilometers. However, it is not uncommon for a belt to “nurse” for 150-200 thousand without deformation or whistling. But this does not mean that the replacement can be postponed indefinitely. This can lead to expensive repairs.
- Mechanical damage. The belt structure may be damaged due to gross errors during installation. This is a mismatch of marks, insufficient or excessive tension of the element. Also, the belt breaks (more often than not it simply falls off) during active driving “before the cut-off”, which is accompanied by sharp braking. If the car is “chipped” with a cutoff offset, there is a high probability of a belt break. Therefore, you should not often operate the car under heavy loads.
What are the signs of a broken belt?
You can determine that the timing belt has broken by the following “symptoms”:
- Abrupt stopping of the engine and inability to start it. Attempts to start the power unit only worsen the situation, since the piston causes new damage to the failed valve.
- After a belt breaks, engine operation may be accompanied by a metallic knock and ease of rotation of the crankshaft by the starter. This is due to the lack of compression in the engine cylinders, as a result of which nothing holds the pistons.
Video: how to determine if the timing belt has broken
The video from the Renault Repair channel describes in detail how to independently determine whether the timing belt is damaged or broken.
What are the consequences of a broken timing belt?
The most serious consequence of a broken timing belt is damage to the valves, as a result of which the car owner is faced with the need to overhaul the unit and restore the gas distribution mechanism. This can happen while the engine is running, when the pistons move continuously from top dead center to bottom dead center. The rupture occurs during the release of gases or fuel injection (at this time the piston moves down). In this case, the movement of the pistons in the cylinder continues and parts of the device collide with each other.
If the timing belt breaks, the extent of the consequences will depend on the characteristics of the engine and the conditions under which the breakdown occurred:
- Due to a broken belt, the camshaft stops rotating, causing the valves to stop in one position. At this moment, the crankshaft continues to move by inertia and the pistons go to the open valves, which immediately bends. On some power units, for example, on the VAZ 2111, 8 cl, the pistons are equipped with special recesses, thanks to which contact with the valves is excluded in the event of a break. But, modern engines are designed to provide the greatest power with a minimum volume, so the pistons do not have recesses.
- If the belt breaks at idle, only a few valves may be damaged. Moreover, the higher the rotation speed of the crankshaft, the higher the likelihood of failure of the guide bushings. This problem causes a major overhaul or replacement of the cylinder head.
- On a diesel engine, the consequences of a broken timing belt will be destruction of the valve, camshaft with bearing elements, cylinder head, connecting rods and pushers. This is due to the design of such motors, due to which the valves have virtually no free play when the piston is in the top dead center position.
- For cars equipped with a Japanese engine, when the timing belt breaks, damage to all valves, breakage of bushings, pistons and cylinder heads are typical. Such malfunctions are typical when the machine is moving at high speed.
How long can you drive on a broken belt?
It is important to know
After the timing belt breaks, you should not attempt to continue driving.
Video: the dangers of a broken timing belt
The video from the Car Program channel describes the consequences that a car owner will face if the timing belt breaks.
Consequences of timing belt breakage and likely costs
The consequences of a break depend on the type of engine, the presence of grooves on the pistons, the quality of the parts and the reasons for the timing belt break.
The most common consequences:
- Buying and replacing a belt
- Engine repair.
Read more about possible engine problems
- Overhaul of the entire engine.
- The need to repair the entire gas distribution mechanism. The most significant problem is bent engine valves that cannot be repaired. This problem most often affects cars in which the combustion chamber is reduced or the pistons do not have recesses. In order to accurately determine the level of damage, you need to take the car to specialists.
- Sections of the piston system are deformed. Such damage most often occurs in Japanese cars. When the blade breaks at high speed, the bushing breaks and the pistons are damaged by the fragments. The consequences are an expensive replacement of all parts.
Diesel engines suffer serious consequences after the fabric breaks.
Car owners will need to replace a number of main parts of the gas distribution mechanism:
- Camshaft.
- Cylinder head.
- Connecting rods.
- Valves.
Costs for eliminating the results of timing belt rupture
The average cost of a valve is about one thousand rubles (excluding replacement). To calculate the total cost, you need to take into account the number of valves that need to be replaced. If there are sixteen of them, the total cost will be high.
Additionally you need to buy small parts:
- Timing belt or complete timing gear kit with all bearings.
- Cylinder head gaskets and manifolds.
- Valve plugs.
- Fasteners.
- Pump (all belt manufacturers recommend changing the pump at the same time as the timing belt)
If the driver carries out car repairs himself, he will also need various tools
What to do after a belt breaks?
If the timing belt is broken, then:
- It is necessary to open the engine compartment and lift (or completely dismantle) the protective cover of the mechanism.
- It is important to carefully evaluate the appearance of the belt (the torn product will be visible). If it breaks at the very bottom, you will need to turn the crankshaft half a turn to find it.
- The vehicle must then be towed to a garage or service station. If the car is equipped with an automatic transmission, the assistance of a tow truck will be required, since towing is not allowed on such vehicles.
How to replace the timing belt yourself?
Good to know
16-valve engines are equipped with two camshafts with a separate gear for each. Before making a replacement, the user should look in the service manual to see where the timing marks are located and what type they look like.
Algorithm for replacement:
- The engine compartment of the car is opened, the negative terminal is disconnected from the battery (the ignition must first be turned off).
- The wheel is removed from the belt side. To do this, you need to jack up the car and unscrew the bolts with a wheel wrench.
- Then the engine cover and the protection of the power unit are dismantled (the bolts or screws are unscrewed). You will also need to remove the generator drive belt. Depending on the design features of the engine, it may be necessary to dismantle the expansion tank with power steering oil or adsorber. In some cars you need to remove the air conditioner bracket, air intake, intercooler with terminals.
- Using a hexagon, it is necessary to unscrew the bolts securing the protective cover of the strap and gears.
- If the car is equipped with a crankshaft position sensor, it is necessary to disconnect the block with cables from the device.
- Then the timing belt tensioner pulley bolt is unscrewed and the bearing itself is removed. If the system is equipped with a guide or support roller, this must also be removed.
- The worn timing belt is being dismantled.
- The position of the mark on one or two camshaft gears is checked (depending on the 8- or 16-valve engine). It is always important to check that these marks match the marks on the timing drive. If they do not match, you need to combine them with each other yourself. To do this, turn the camshaft with a key.
- If you need to check the alignment of the marks on the gears with the mark on the oil pump body, you must remove the toothed pulley with a special washer. If the screw does not come out, rest the handle of the L-shaped key against the rod, connect the battery and crank the starter once. After this, the battery must be disconnected.
- The next step is to install the support roller, if it is provided for by the engine design.
- The new belt is first placed over the crankshaft sprocket and then wound onto the support roller, camshaft sprocket and pump gear. When performing this task, you should monitor the location of the marks on the camshaft gears. If the risks have gone astray and no longer match, they must be set again.
- Next, install the tension roller and tighten it (you need to screw it without tightening it until it stops).
- Check the evenness of the belt lining. Then it is tightened using a special wrench (the roller must be turned counterclockwise). Next, holding the latter with a tool, you need to fix its position by tightening the mounting screw (all the way).
- The product tension is diagnosed - you need to turn the belt lengthwise using your fingers. It should rotate no more than 90 degrees.
- At the final stage, it is necessary to return all removed parts and spare parts to their places.
- The engine is started and its operation is assessed (by ear). If the product is installed correctly, there should be no abnormal sounds.
When installing the timing belt yourself, it is important to pay attention to:
- the presence of a hum and whistle of the roller, which indicate the belt is overtightened;
- detonation - weakening of its tension;
- black smoke from the exhaust pipe - incorrect markings on the shafts.
Possible costs and belt replacement procedure
The cost of one valve, excluding additional costs, averages a thousand rubles, and considering that all 16 may need to be replaced, you can imagine approximately how much the repair will cost.
In addition to the accompanying little things, you will need to purchase:
- A new belt, or a timing belt kit with a tensioner and idler pulley.
- Gaskets for intake and exhaust manifolds.
- Cylinder head gaskets and valve covers.
- Set of mounting bolts.
- Possibly the water pump (Pump), if wear is suspected.
The easiest way to perform the replacement operation is on a lift. To work you will need:
- a set of keys
- screwdriver
- locating pins for timing marks
- in some cases special tool.
To remove the old belt, follow the following action plan:
- Remove the timing case - secured with several bolts.
- Unscrew the crankcase protection bolts.
- Next, remove the compressor belt. To do this, dismantle it, remove the belt and install the compressor in place.
- Remove the alternator belt.
- To disconnect all contacts, remove the terminal from the battery.
- Unscrew the mounting bolts from the engine and remove the generator, terminal and pump pulley, remembering to first remove the bolts holding them.
- It may be necessary to remove the engine mount.
- Remove the protective cover from the timing belt
Now proceed with the actual replacement, for which you will need to remove the timing pulley covers and pull out the old timing belt. Put a new one in its place and tighten the tensioner. If the rollers become unusable, they should also be replaced. Next, assemble the structure in reverse order. Keep in mind that each car brand has its own characteristics of removing and installing the timing belt, however, in general they are very similar.
Preventive measures
Good to know
The main preventative measure for timing belt breakage is its timely replacement.
Additional preventive measures include:
- Use of high-quality original spare parts.
- Periodic monitoring of the tension level of the product, the condition of the pump and rollers. It is important that the tension is uniform in all areas, without sagging.
- External assessment of the belt condition. If the first signs of damage and cracks appear on the product, the user needs to replace the timing belt as soon as possible.
Reasons for the break
Most often, valves bend due to a broken timing belt, but few people know why it breaks. Naturally, the top cause of this malfunction is operational wear. It is important to understand that a rubber belt, even of high-quality production, is not capable of driving more than 70,000 kilometers, so it needs to be changed every 60-65,000. It is possible to determine that the drive should be replaced ahead of schedule using its detailed inspection. The surface of the belt, at a minimum, should not contain any cracks, torn teeth or oil stains, and, at best, no wear.
In addition to wear and tear, the timing belt can break for the following reasons:
- wedge of the gas distribution mechanism due to its internal breakdowns (rollers and tensioner often suffer);
- installing a drive with weak or excessively strong tension;
- frequent operation of the machine under heavy load conditions;
- violation of the tightness of the engine protection;
- oil getting on the belt due to leaking gaskets or worn seals.
Complete elimination of the factors noted above, timely replacement of the belt and the use of only high-quality parts is exactly what will help reduce the risk of its breakage to a minimum. Otherwise, you should prepare for the consequences that occur when the timing belt breaks.
