Immediately from the threshold it must be said that a visit to the service station with complaints about the rumble of brakes in 100% ends with the same diagnosis. As a rule, all that the masters offer is the replacement of pads and discs. Unfortunately, this problem is far from being so simple as to be solved without fail by such banal methods. Although, in about half of the cases, it can still help. Therefore - do not rush to the service station. Despite the fact that these are brakes - dangerous and all - sometimes it is much more effective and cheaper to eliminate the hum on your own. The main thing is to know in which direction to "dig".
Specific hum conditions
It is also worth noting that this article will consider the possible causes of only one particular type of brake hum. Namely, when it manifests itself only after an intense ride. This can be a long movement in urban mode, where acceleration and deceleration alternate one after another. It also includes a hum that occurs after a few moments when you press the pedal when driving at a solid speed.
Any other noises - rattling, whistling, grinding, rattling - if it is possible to "cure" after reading this material, then this should be taken as accidental luck. The article is also not about the vibration of the brake pedal and the beating of the steering wheel. By the way, all of the above is much easier to diagnose than when the hum when the brake is pressed occurs precisely under loads. We will try to solve this particular problem further.
All possible causes of the hum
As in the case of any other car breakdown, the most efficient way to search is to have a list of all the most likely causes in your arsenal. When you have such a “cheat sheet” on hand, it remains only to methodically work out each of its points, and the solution to the problem will not take long.
“Digging” with the hum of brakes is reasonable in the following directions:
- Dubbing pads.
- Overheating drives.
- "Boiling" brake fluid.
- Aspen leaf effect.
- Wear and other disc defects.
- Wedging guide calipers.
- Wheel bearings under load.
If the brake system is a dark forest for you, and the listed items on this list do not tell you anything, below, attention is paid to each of them. Including, in understandable words, it is told where it is located, how it affects the buzz, by what principle to confirm or exclude the diagnosis, and also literally in a nutshell about the “treatment of the disease”.
About such assumptions of "specialists" as dead "grenades", some kind of rubber is not the same, worn pads and other crap - you will not find anything here. Such pseudo-reasons have nothing to do with the problem under consideration. They are often mentioned, of course. But this is only to have more text. At the same time, the real possible reasons are not even mentioned.
This item includes both tanning pads, as well as hardened and life-long oak. First, let's take a look at how they differ. Oak pads for life are called brake pads, which already from the box do not correspond to the required hardness indicators. Experienced motorists easily identify them, as they say, by touch, as well as by sound, by lightly hitting a couple against each other. Also, such pads quickly and unevenly crumble, chip off and cannot effectively slow down a priori.
Tanning pads are those that are prone to change in hardness under load. I mean, they're good on their own. But, as soon as heating occurs as a result of friction against the disk, the material immediately tans. Usually cheap fakes that sell for a few dollars a pair suffer from such a sin. It is clear that for such money they can be made either from baked horse manure, or from worn-out pencils for drawing.
The last option - zadubevshie pads. These out of the box can work fine, do not hum, cool cool and so on. But if you bake them a little, braking vigorously a couple of times between traffic lights or at high speed, they become harder than a diamond forever. Keeps them out even when they are cold. Unfortunately, such pads come across both among branded models and original ones.
Whichever option is in your particular case, the hum of the brakes is provided. Even while the pads are cold, they can “be silent”. But as soon as you drive among dense traffic, between traffic lights, or try to stop quickly from a speed above 120 km / h, an impressive rumble begins to be heard. It feels like it sometimes comes to the point that the sound diverges through the body, leading to god knows what terrible thoughts.
How to understand that your pads are harder than a coffin nail? As mentioned above, an experienced motorist who holds them in his hands not for the first time in his life will most likely be able to determine this. If there is no experience, then the chances are zero. Perhaps elementary logic will help - if the pads were recently changed, and the hum appeared, obviously, someone saved on new spare parts.
One way or another, there is only one way out of this situation in both cases. The pads need to be replaced. If you are not sure that it is they who are to blame for the hum, first work out the remaining 6 points of our “cheat sheet”. Perhaps the problem is not hidden here.
First, overheating discs are extremely inefficient at stopping the car. And all because the brakes are a converter of kinetic energy into thermal energy. When there is nowhere else to put the excess heat, the transformation becomes dull, and sometimes it stops altogether. In fairness, it should be said that critical overheating of disks is not always a breakdown. All brakes have a certain reserve, which can be easily exhausted with aggressive driving. That is why sports cars have such high requirements for these parts - they are made of ceramics and other "nanomaterials", larger in size, and so on. All for the sake of cooling.
Secondly, overheating drives can and will hum. This is the norm. Deviations from it are only those cases when overheating occurs inadequately quickly. For example, a couple of traffic lights, and that's it - a rumble and floating brakes. If so, then there is a reason to check the discs for wear or uneven output. A few words about this are said below.
"Boiling" brake fluid
If you ask hundreds of car owners who change their brake fluid at least once every two years, what do you think the answers will follow? And you yourself - how often do you change it? Let's be honest with ourselves. That rare motorist who generally changed the brake fluid at least once in his life. The main thing is the oil. And the rest, even though the grass does not grow, as they say.
Meanwhile, brake fluid is by no means eternal. It, like engine oil, works out its resource and loses its properties. And it doesn't matter what she looks like. Many people think that crystal clear, not discolored and not cloudy brake fluid is an indicator of its suitability. But it's not. Like all other working fluids in a car, it is subject to periodic replacement, followed by bleeding the system in order to remove air. How often should this be done? Ideally, at least once every two years. What's more, it's not that expensive. And yes, there is a bit of it.
And now back to our problem - the hum of the brakes. It may very well be that such a defect occurs due to a liquid that has lost its properties. It is often said that under load it “boils”, as a result of which it ceases to perform its functions. The hum is also quite reasonably present. Therefore, if you have had a car in your hands for more than two years, and you have not changed this consumable, there is no point in moving on to the rest of the items on our list. Replace. Even if it doesn't help, fresh brake fluid won't hurt your car anyway.
Aspen leaf effect
Motorists call this lyrical definition the effect when the brake disc, being sandwiched between the pads, begins to tremble like an aspen leaf in the wind. Often this defect is accompanied by a hum. It does not always appear, but just after a good load, which the brakes are subjected to in urban driving. Unfortunately, the "aspen leaf" cannot be seen. Moreover, it does not always manifest itself in the form of a standard vibration on the pedal.
However, you can indirectly understand that this effect is present on your car. For example, if the discs are worn out beyond the norm. You can check this with a caliper. You need to measure the thickness of the disks. Here you need to know that they are ventilated and non-ventilated. The first differ from the second in the presence of ventilation holes, which can be seen if you look at the disk from the end. The normal thickness for the first is 18 mm, and for the second - 10 mm. If you have noticeably less - the effect of "aspen leaf" is provided. And with it, the hum of the brakes when you press the pedal.
What to do with such a diagnosis is probably obvious. Worn discs can only be exchanged for new or used, but in good condition. By the way, sometimes the second option is preferable. Especially if you want it cheaper. Buying the newest and cheapest is a bad decision for any car part.
Wear and other disc defects
There are several varieties of wear on brake discs, due to which a hum can be heard under the conditions described. The first of these is the so-called furrows. They are clearly visible to the naked eye, sometimes even right through the rims. They are there for all sorts of reasons. The most obvious is getting between the pads and the rotating discs of some kind of abrasive. Coarse-grained dust, sand, dirt, small pebbles. All this is able to "register" circles on the water on the disks.
The second type of development is a protruding edge. Such a defect leads to a hum when pressing the brakes, as a rule, when the pads change. Very often, these parts are not bought in size, which, however, does not interfere with their successful installation. As a result, the pads do not properly contact the discs, can overheat, wear unevenly and bite each other. Which of these causes the buzz is not really important.
The next defect is corrosion. It is observed in the form of small pits directly on the working surface of the disks. With a certain degree of severity, it can also cause the hum of the brakes. Again, the root cause is overheating under load. Parts overheat, hum occurs, and braking performance may also deteriorate.
The next possible problem with discs is when they are burned or set on fire. You can identify these by blue or iridescent spots right on the work surface. Such “burns” are said to indicate that the brakes have been overloaded once or repeatedly. As a result, inadequate wear or deformation should be looked for. In any case, this may well be the reason why the brakes are buzzing.
In all these situations, the "treatment of the disease" is the same. It's a brake pad replacement. It should also be understood that after working together with defective discs, the pads are also very likely to become unusable. It is not worth using them with new disks. It is better to immediately replace with new ones. Fortunately, even in high-quality performance, these consumables do not cost space money.
A few words, probably, should be said about the groove of disks, which is used by many motorists. Unfortunately, this repair method is justified only in 1 case out of 10. And even then, if the groove was entrusted to an intelligent turner, and did not try to “align” the disk with a grinder right on the machine. The latter is strongly discouraged. The braking system is a mechanism that does not forgive inaccuracies. A grinder and accuracy are antonyms.
Wedging guide calipers
This problem occurs in several different stages of complexity. For some, the calipers are jammed so that the brakes continue to work quite intensively even when they are not required to. For others, the pads, albeit effortlessly, are still in constant contact with the discs. It is clear that all this leads to chronic heating of the parts of the brake system, and while pressing the pedal under normal load, a hum will be heard.
In most cases, wedging of guide calipers is easily “treated” with your own hands. For this you need:
- Make sure the anthers are intact.
- Carefully inspect the guides for blockage or corrosion.
- If the last two are present, clean them up.
- Lubricate guides.
In fact, due to the not very comfortable conditions in which these parts of the brake system are constantly located, wedging is a common cause of buzz. Anthers are destroyed, cracked, slip. The grease is washed out with water. Dust and dirt accumulate on the “mirror” of the guides. Next comes corrosion and the corresponding consequences. Therefore, if the repair is successful in this direction, do not forget to periodically check the guides for the integrity of the anthers and the presence of lubrication. After all, problems can be tougher than some kind of hum of brakes.
Attention! Very often, when manipulating the brakes, motorists use the well-known WD -40 or analogues. Yes, it helps to develop soured parts quite well. But she also “likes” to get on the brake discs, which subsequently completely deprives the car of brakes for some time.
Wheel bearings under load
It’s probably worth starting with how couch experts refute this reason. Such experts say that wheel bearings cannot make a hum exclusively when you press the brake pedal. That is, if a scribe came to them, then they make noise during a simple ride. In fact, this is, to put it mildly, a delusion.
Wheel bearings can only hum under loads. This happens to them when they are just starting to become unusable. That is, in the normal driving mode, they are “silent”, and even the swaying of the wheels on the jack from side to side shows that everything is fine with them. But the loads for wheel bearings are two modes:
With turns, it should be clear without explanation - under the action of centrifugal force, the mass of the car shifts, unloading one side of the suspension, and loading the opposite. But the same problem happens with braking. When the car slows down, its weight shifts sharply along the motion vector. As a result, the front wheel bearings experience increased loads. The result is a hum, the cause of which we are trying to find here.
Actually, if the search for a problem points to this point, then, in principle, you can rush to replace the “weak link” and not rush. Recall that here we are considering only such a hum of the brakes, which appears only after a good load. Accordingly, if the wheel bearings are to blame for it, then they are more likely to still be like, as they say.
To identify the cause of brake hum, you first need to determine the conditions under which it occurs. That is, if the noise is heard not only after loads, or has a different sound character, then the technique considered here is not the most effective. Or rather, not complete. These reasons should be worked out only in cases where the hum is heard after aggressive driving, and its root cause may be overheating of the brake system parts.