What could be rattling in the back?
As you understand, the suspension device as a whole is quite complex, it is a certain set of mechanisms and devices that are a link between the body and the road itself, through the wheels. If we compare the design of the rear, then in many ways it is simpler than the front. Units can fail for a variety of reasons. And the “first sign” of the appearance of any problems is considered to be a roar coming from the back.
Not only the suspension can be to blame for this. So, you must first discard:
Unsecured tools in the trunk, under the false shelf. It is not uncommon that could disrupt the spare tire mount.
The exhaust pipe broke off.
Not fully fixed back of the rear seat causes trouble.
And exotic, like a torn off or not screwed bumper.
By the way, the last reason, oddly enough, but in large numbers is found on domestic cars, the Samara, Tens, Priors families. The reasons lie in loose bolts or worn rubber bands.
If, after the inspection, none of the above could be found, it is necessary to start diagnosing the complex as a whole, while it is important to pay attention to each mechanism.
Faults and solutions
Let's make a list of the most common suspension problems that can cause knocking and other unpleasant surprises for the driver. Let's briefly analyze the features of the repair. So:
1. Cushioning. As a rule, most drivers face them. Because of what the wear of the elements occurs, it is not difficult to guess, bad roads, not a neat ride. Try to be as attentive as possible to such nodes, not only the presence or absence of ill-fated sounds, but also maneuverability and, in general, controllability depend on them.
A great misconception among domestic motorists is that racks can only knock at installation sites. In addition to fastening, from above, from below, the rod entering the piston can knock, the gasket (sleeve) “ate” and it began to hit the body. The problem is difficult to notice, without a full diagnosis and removal of the entire assembly.
If the rack turned out to be the real culprit, that is, the bolt is untwisted from below or from above, then it is enough to tighten it, replacement is not required. When the problem is in the rod itself, it is more efficient to replace the entire assembly, without disassembling the shock absorber and repairing it.
On most cars, the rear pillars are attached to the body through a rubber damper, also known as a compression buffer, that is, an ordinary rubber “washer” 2 to 5-6 cm high, depending on the model, put on the stem. Often the rubber material is not of high quality, as a result, the gasket becomes stiff, and no longer copes with its absorbing functions. Replacing the rubber will solve the problem.
2. Springs. Depending on the modification of the machine, they can be installed either separately from shock absorbers or paired with them. Pay attention to the suspension structure of the VAZ 2110 and similar, they have a shock absorber that comes with. In another car, let's take Daewoo Lanos, the strut and spring are installed separately. In principle, in our case there is no global difference in this.
Pay attention to the state of the coils, count an equal number, because it often happens that a couple of coils break off, the spring bursts.
Pay attention to the condition of the gaskets, rubber or polyurethane inserts for springs often crack, break, wear out. For example, if the wear is serious, the sharp part of the coil can “get” to the metal “cup” and beat against it.
3. Silent blocks, levers, beam.
It's hard to imagine them apart. Worn ones are repaired in one way - by buying new ones. In durability, polyurethane parts cannot please, they very, specifically endure all the hardships of domestic road surfaces, especially outside the city.
It is easy to diagnose a malfunction, if there is play at the junction of the levers (guides), then the silent block needs to be replaced. The development of gum, bushings leads to direct contact of metal elements.
With levers, the same troubles arise, for example, after a strong blow, the lever could be deformed, which is why, when the car was moving, it began to touch other parts. The fastening loosened, a crack appeared. In such cases, a complete replacement is recommended.
In addition, do not forget about the installation sites of the same beam.
On models from the VAZ 2109 family, these “ears” were often torn off.
This also includes troubles with, the rubber seals “ate”, the mount, the stem broke, which can also cause a knock.
4. Hub bearing
Yes, they can also cause strange sounds. The impact on them is incredible, so keep an eye on their condition. Try to shake the wheel, if there is play, then it is likely that knocks will be felt even on small bumps.
In the photo - the hub and wheel bearing
5. Really rare problem with brake calipers, pads, discs. Knocking may occur due to unscrewed caliper bolts, which is why, when driving and during braking, it will beat against the “drum” or disc.
Poor quality pads can delaminate, which is why they knock no less loudly than any other part. In the case of calipers, it is enough to tighten them, the pads will have to be changed. The disk can similarly unscrew, delve into the little things.
6. The bolts of an unturned wheel are knocking, no matter how ridiculous it may sound, but it happens that the sound appears due to the loose wheel fasteners. Exit, tighten and check.
Conclusion
A knock in any part of the car always signals the driver about the need for inspection, a thorough diagnosis of the car, so you should not discard the inspection for later. Over time, the situation may worsen and a simple replacement of the hub bearing, compression buffer, silent blocks is not enough.
Structurally, the rear suspension of the car is much simpler than the front. However, this does not mean at all that there is nothing to knock on there. Knocking in the rear suspension usually becomes audible at the moment when repair is required. In the front chassis, you can feel the impact on the steering wheel, pedals, body, and the sounds are closer. In the rear, the sounds are reverberated into the trunk, where it is difficult to hear them. And when the driver needs to transport something long and the seats fold down, then the knock becomes well felt and the understanding comes that there is a problem. And if by the type of knock in the front suspension it is not difficult to understand what happened to the car, then in the case of the rear suspension, the diagnosis is more difficult. But you can understand the reason.
The easiest and most reliable way to diagnose a knock in the rear suspension is manually, but this is if it is not possible or you do not want to go to the service station. There are also diagnostic stands that will determine any suspension problems without errors. It's not worth driving with knocks, although the rear suspension may seem not very important - in the future this can lead to undesirable consequences.
Reasons for knocking
Even in a simple rear suspension, there are shock absorbers, springs, brackets and silent blocks. There is something to knock. If it knocks quite often, then you need to take a little time to diagnose.
What to check first?
You should start self-diagnosis not from the rear chassis, but from the exhaust system. Check the exhaust path from beginning to end. Very often, rear suspension thuds are caused by the muffler and not elsewhere. To do this, they drive the car into a pit or lift it on a lift, carefully check the fasteners and all the details of the exhaust system. Next, pump the exhaust pipe. If it does not make any sounds and does not hit the bottom, then everything is in order - you can move on.
Next, check the trunk. Experts recommend paying special attention to the places where the spare wheel is attached. A tool can get into a niche and provoke sounds similar to the knock of a suspension. But if these checks did not give anything, then you need to move on and already diagnose the elements of the rear chassis.
Checking the mounts
One of the popular causes of knocks in the rear suspension is a beam. If the rear suspension in the car is exactly like this, then you can accurately determine what is knocking. The car is driven into a pit or overpass. Next, you will need the help of an assistant - he must rock the car. The driver must be in the pit and touch the various nodes of the rear beam. Most often, silent blocks of the rear beam knock. Knocking is also provoked by levers, but here the diagnosis is more complicated.
Checking the levers
The car is driven into the pit and a gear is installed at the checkpoint - in this case it is better not to use the handbrake. For diagnostics, you need a mount. With its help, the serviceability of silent blocks and bushings in the levers is checked. If there are backlashes, then the bushings must be changed.
Suspension arms need to be checked for integrity. Often when driving, these parts are deformed. This can lead to knocking in the rear suspension. Cracks will indicate the need for urgent replacement of the levers. The lever fasteners can relax during the ride - if so, then they are tightened.
Deformed levers can knock when driving on the body. Knocking is also emitted by other parts in the rear suspension. This is determined by the buildup of the car.
This simple method of diagnosing buildup allows you to quickly and without serious costs get the most complete information about the state of the suspension. But you should not expect a miracle - not always a car will reveal all the secrets so easily. It happens that the knock of the rear suspension is heard while driving, but nothing is heard in the pit or at the service station.
Checking racks and supports
If the racks make a strange sound, this is determined quite simply. When the car is rocked, you need to attach the wooden handle of the hammer to the rack and feel if the knock is given to the object. It is possible that deformed or sagging springs sound. Loose rack mounts can also really knock.
There are also problems in the upper mount of the rack. The upper mount is broken - this can be seen from the trunk. You need to put your finger on the mount, and then rock the car up and down. If the lower fastener has lost its elasticity, this is checked in approximately the same way, but already on the bottom of the pit - a finger is applied to the fastener from below.
The rack itself may also fail. This is determined when all other options for the appearance of a knock in the rear suspension are excluded. Then you need to change the shock absorber on the car.
Next, check the springs - they can make a variety of sounds. The coils beat against each other, there are various problems that lead to the breakage of the spring. To carry out a full diagnosis, you need to disassemble the parts, but this is usually done when nothing helps. Pay attention to the integrity of the rubber gaskets, which are sometimes installed from the factory on the top and bottom of the spring. They smooth out impacts on the body during suspension operation. If there are no such elements, it is likely that sounds arise precisely because of this.
It often happens that a knock in the rear suspension appears only when driving, and during the diagnosis everything is in perfect order. Then the spring needs to be disassembled.
brake calipers
This situation is possible on some models of cars with rear disc brakes. The reason is loosening or play of the calipers. This is a common problem for budget cars. It is inexpensive fasteners that often lead to failure of parts. Often such knocks are very difficult to diagnose. You will have to perform a whole series of operations.
First of all, pull the caliper with your hands with the wheel screwed on. There is a chance that these parts are beating against the brake disc. But everything has to be tight. Then they remove the wheel and carry out a manual diagnosis of all caliper mounts - they pull the mechanism with their hands and check the backlash.
Next, the caliper is disassembled to reveal the relaxed details. Particular attention should be paid to the quality of the tightening of each module and element, each bolt. This may suggest the nature and cause of knocks. It is necessary to pay attention to the brake pads - perhaps they are worn out or deformed and knock in their place when driving.
In the case of drum brakes, everything is much simpler. None of the elements in this mechanism can provoke knocks. This is possible only when the drum has crumbled. But you don't need to discount the brakes, especially if you hear a knock in the rear suspension when braking. The pads have already been said and now we need to consider the situation in more depth.
Brake cylinder
Knocks can be provoked by the brake cylinder if it is not working. For diagnostics, the car is raised with a jack or on a lift, then they look at how the rear wheels grab when the brake is pressed. The cylinder can wedge and then hit the drum with a block. Next, the block returns to its usual position, but slowly. And at that moment, sounds are heard.
brake force distributor
Knocks can be provoked due to a malfunctioning "sorcerer". When braking hard, the rear will skid, as one wheel is skidding. "Sorcerer" can jam, and he abruptly loads one of the wheels, and then does not want to let go.
What else can knock?
There are also the most incredible causes of knocks that drivers have been looking for for years and cannot find. If there is even a slight knock in the rear suspension, then over time it will intensify, and it can be localized. But worse, when this knock does not change. Additional checks are needed.
Often the reason is a loose wheel after a tire fitting. Also in the trunk there may be metal parts that knock two against each other - in the cabin it seems that this is a knock in the suspension. The spare wheel can knock against the housing for it. The body itself can also knock. And the muffler - it often vibrates.
All these reasons are checked first at the service station. So you can understand where the knock of the rear suspension comes from when driving on small bumps, without even going to the suspension diagnostics. You just need to normally look for the cause and have more information on how to solve problems.
The cause of the appearance of a knock in the suspension of a car is most often the shock absorber struts. At the same time, such a knock is characterized by the fact that it appears only on the side where the rack is faulty - which is why it is usually heard how it knocks distinctly either in the front suspension, or in the rear, or in front or behind.
Most often, a knock in the suspension appears only on bumps. In this case, the culprits of such a knock may be:
- worn or damaged racks, as mentioned above;
- worn or damaged sheets of springs of the bracket fastening them;
- worn or damaged control levers (in this case, a knock in the suspension can appear on bumps only when turning the steering wheel and only in front);
- broken or damaged ball joints;
- broken shock absorbers also often cause knocking;
- loose or damaged body mounts - a manifestation of knocking is also only in the front suspension.
When it comes to diagnosing knocking noise when driving over bumps, the most obvious thing that is required is a road test to determine the source and nature of the sound. Before you take your car to a road test, you need to walk around the car to make sure nothing falls off while driving. Look carefully under the bottom of the car.
A soft thud in the suspension due to the struts
Apply pressure to the front and rear of the vehicle. This will determine if the racks are working properly. With properly working struts, the body of the car will rise after you stop putting pressure on the car and return the body to its original state.
Motorists, and especially beginners, are afraid of anyone when working or driving a car. Often, when driving, an incomprehensible knock of the front suspension on small bumps at different speeds may appear. Inexperienced motorists immediately go to the service station to solve problems, but in most cases, specialists do not find anything after the part. But the knock remains, and something needs to be done about it. Do not rush to buy new parts for the chassis. It may well be that the cause of this knock is a mere trifle, a trifle. Let's try to understand this issue, because the price of the front suspension is quite serious (repairs cost up to $ 500-1000), so it is so important to find the cause yourself.
Common Causes
Sounds may appear due to a defect in the suspension.
Silent blocks are often the culprit. As a result, the car does not drive well. It can also knock due to the loss of elasticity of the spring that works in the front suspension.
How to check silent blocks?
A flat mount will be required for diagnosis. It will allow you to determine how much these parts are worn out. With the help of the mount, the lever will move in the longitudinal and transverse direction. If there is play or damage, then it is the silent blocks of the front suspension that are to blame for the knock.
Sometimes levers can be collapsible. Then you can do it. To do this, the lever is dismantled, and then, using a special mandrel, the part is squeezed out. It is advisable to lubricate the new silent block before installation. The landing surface must also be cleaned. After installation, knocking should stop.
Steering
Even for experienced service engineers of numerous car services, finding the cause of extraneous knocks is a serious problem. Many immediately recommend replacing the shock absorber strut. Here it is, new, standing on the car, and an incomprehensible knock in the front suspension on small bumps has not gone away. The car owner goes to another service, but there he is offered to replace it, but even after that the knock does not disappear.
When diagnosing the front suspension, experienced car owners begin the check with the steering system.
Often it can knock and the sound can be easily confused with how the shock absorber strut knocks. If it is heard on a shallow gravel road, then this is definitely a steering rack malfunction. In this case, the sounds will be heard only from one side. In addition to knocking, you can feel vibrations on the steering wheel.
The main causes of vibration in the steering
Among the popular reasons that cause a small knock in the front suspension on small bumps, there is a large gap between the steering rack and gear. This is the result of wear and tear. To make an accurate diagnosis, it is recommended to pull the steering rods up and down. At the same time, carefully observe the movement of thrust. If she doesn't move, then she's fine. If the thrust will hang out, then, most likely, the wear of the bushings is here.
If the rack turns, then the exact diagnosis is a large engagement gap. But this problem is easily eliminated by tightening this very rail. Also, pulling the steering rod, you can see broken or too worn bushings for fastening the steering rods to the steering rack.
Another possible cause of knocking is the steering joint. To test this hypothesis with two hands, it will be quite difficult to cope. You need the help of a friend. The assistant must turn the steering wheel very quickly and sharply, and the car owner must grasp the hinge in such a way as to hold the hinge itself, its body and finger. If there is wear, then play can be felt. Then the suspension repair will not be needed in the near future, and only the hinge bushing will have to be bought and replaced.
Upper rack support
It can also cause knocking in the front suspension over small bumps. On automotive forums, the topic dedicated to this knock is very popular. Everyone has different reasons. In the course of trying to combat this annoying sound, car owners sort out the entire suspension, but often the knock remains.
One possible cause is the top support of the rack. It consists of a rubber part as a damper and a bearing. If this rubber element has lost its elasticity, then this is the reason for this extraneous knock that all drivers struggle with. In order to find out exactly if this is the case, measure the gap between the limiter and the support. In most vehicles this is easy to do, but in some models this assembly may be closed. If measurements show that the gap is more than 10 mm, then the support must be urgently replaced. However, this gap is not always uniform. When measuring, it is recommended to focus on the average figure. It is worth checking this support carefully: on many cars this sound appears only on one side.
Cause of the knock
Why is it knocking? Here, at first glance, metal parts cannot collide. However, the hydraulic system of shock absorbers does not dampen sharp, but short movements of the rod. This function is performed by rubber supports, which must have the necessary level of elasticity. If the supports are too extended, then they will inevitably lose their energy intensity. They process blows worse and give them to the car body with an indignant thud.
Worn support bearing
These sounds appear in the same way as with an inelastic damper, but they are sharper and much louder. In order to make an accurate diagnosis in this case, it is necessary to remove the rack. In this case, it is recommended to take into account one rather interesting feature that is inherent in such breakdowns: bearing wear is always uneven. So, the maximum wear is where it is constantly located when the car is driving straight. If after turning the steering wheel the knock disappears for a while, then it's definitely a thrust bearing.
There is also another diagnostic method. It is quite old, but effective. Again, you will need an assistant. The second person should rock the car up and down. The driver must at this time feel the shock absorber rod with his hand. The knock will be transmitted to this rod.
If we compare these knocks in the front suspension when turning the wheels at different angles, then we can draw some conclusions about the state of the support bearing.
Another possible reason is a weak tightening of the nut on the upper support, sometimes it happens.
Spherical bearing
On car forums, in topics devoted to this knock, a variety of reasons for knocking in the front suspension are discussed. Ball joints are one popular reason. You can say even more - this is a classic among all possible sources of extraneous knocks.
But there is one peculiarity here. On front-wheel drive cars, knocking from ball joints is a rarity. It is more typical for classic VAZ models.
For example, a worn hinge can cause harsh vibrations when crossing small bumps in the road. Diagnosing this malfunction is quite easy - pull the front wheel in a transverse direction. Naturally, for this it is desirable to raise the car. Beginners may confuse play in the ball joint with wheel bearing movement. In this case, the assistant must hold the brake before jerking the wheel, this will eliminate the play of the hub.
Sometimes extraneous knocking can be caused by a real trifle - check the rubber anthers. Hinges cannot last long if the protective cover is torn.
Rack
Very often, a knock in the front suspension on small bumps is attributed to this particular node. In reality, the stand is the source of knocks in very, very rare cases. But it’s worth checking, because this is a very important node.
A badly worn, very weak stance, even though it hasn't leaked yet, can cause bumps. When the car moves, and the wheels fall into the pit, the rebound force of this rack is not enough, and it is not able to prevent the spring from straightening. The rack shoots wheel down. When the wheel either touches the pit or hangs in the air, it stretches to its maximum. The blow will be in the first and in the second case.
Methods for diagnosing a rack
There are a lot of methods. Classic - swing the body down, and it should smoothly rise to its normal position and stop. If so, then the rack is OK.
It happens, although quite rarely, that the rack makes extraneous sounds due to its internal problems, for example, the nut that holds the piston is unscrewed. However, this does not cause knocks. When driving, the car sways, controllability drops. In this case, the replacement of the rack and suspension repair.
Various breakdowns of the shock absorber are the consequences of its illiterate use. The oil in these systems must have a specific specific viscosity, which also depends on the air temperature. Warming up the engine, the driver immediately takes off, but the oil in the rack has not warmed up. If it's cold outside, then the viscosity is too high in the rack. In this case, thin and very fragile parts fail.
Thick oil may also be unrelated to the weather. Sometimes excessively thick liquid is poured into the shock absorbers. They do this to increase the resistance force and so that the oil does not "run away". But as a result, stability and controllability deteriorate, because hard does not mean good.
Unpopular reasons for knocking
It would be quite useful to check the bracket. This part consists of bushings based on metal and rubber, which are deployed in different directions and connected by a thin isthmus. Most of the time it breaks down. On rough roads on small bumps and corners, you can hear a knock.
For a correct diagnosis, with one hand, you need to pull the end of the stabilizer. It will work better if the wheels are turned to the right.
It happens that the supports wear out actively moves at an increase in speed, on bumps. At certain moments, he reaches the body with a generator and an oil pan. The result is knocking. This source of knocks is rarely guessed at. Many change the suspension, but replacing the front suspension does nothing in this case.
In cars, anything can knock. For example, washer barrels. If it is poorly fixed in place, then the rut will knock. Still there are many all sorts of mysterious culprits of such sounds.
Brakes as a source of noise
Sometimes sounds coming from the suspension actually come from the brakes. It happens that the motorist checked everything, replaced everything that can be replaced. The scheme of the front suspension has already been learned by heart, and the knock has remained the same as it was.
To make a diagnosis, you need to move. If it disappeared, and when the pedal was released, it resumed again, then the brake pads are to blame. The same problems can occur after installing new pads.
If the car knocks, do not rush to make repairs to the chassis. Perhaps the extraneous sound is caused by a completely different reason. In this case, only a complete diagnosis can help. It may be enough to replace the front suspension silent blocks, and the sound will disappear forever.