Jamming brakes is a very unpleasant and potentially dangerous breakdown. It consists in the fact that the pads are pressed against the disc with force, regardless of whether you press the pedal or not. In most cases, the brakes do not stick critically, and only on one wheel. This allows you to move on without noticing the problem. With a serious jamming, characteristic signs appear, which are simply impossible not to notice. What are these signs, why the brakes stick, how it can end, and what to do if a problem occurs on the road - you will learn from this material.
The device and principle of operation of the braking system of the car
Even superficial knowledge about the device and the principle of operation of the system is enough to make the right decision when the brakes jam on the road. Including, it will help to safely get to the house, to avoid serious losses and costly repairs. Thoroughly studying the topic is not necessary. This is for professional mechanics.
The most common disc brakes consist of the following four elements:
- Brake discs (19).
- Brake pads (6).
- Calipers (13).
- Drive mechanism (15).
Brake discs - mounted on the wheel hubs and rotate with them. When the brake pads press against the discs, the car slows down. To ensure that braking occurs only when the pedal is depressed, the pads move freely along the guides. The caliper is a kind of housing for mounting parts of the brake mechanism. Fastened to the drive mechanism with bolts. To press the pads against the disc and start braking, the system uses a piston. It moves inside the drive mechanism under the influence of brake fluid pressure.
The piston and caliper guides are high-precision parts that must work in "sterile" conditions. To protect these elements from dirt and moisture, rubber anthers are used.
7 signs of car brakes jamming
In practice, the most common signs of jammed car brakes are:
- Deterioration of rolling.
- Wheels are shaking.
- The car pulls to the side.
- Vibration and vibration of the steering wheel.
- The smell of burnt pads.
- Extraneous sounds.
- The car jerks while driving.
When driving in neutral without pressing the brake pedal, there is a feeling that the car is slowing down. Experienced motorists can determine the deterioration of rolling by two more signs. Namely, by the increased fuel consumption and by the operation of the engine, which, so to speak, strains out of the blue, as if the car is going uphill. Also, the car does not try to roll when it is on a slope without a handbrake and in neutral.
Wheels are heated
After intensive braking, all wheels are warmed up. This is the essence of the work of the brakes - the kinetic energy is "utilized", turning into heat. But. When a wedge occurs in one of the brake mechanisms, the corresponding rim will be significantly hotter than the others.
For more information on why the wheels of a car are heated, see the link.
Car pulls to the side
This is because one wheel slows down, which means it tends to travel a shorter distance than all the others. This symptom is especially evident on rear-wheel drive cars when one of the front brakes sticks.
This symptom is manifested not only because of the brakes. It is described in detail in the material - why the car pulls to the side.
Vibrations and steering wheel
When the front brake sticks, they are transmitted and felt on the steering wheel. With a rear brake wedge, the entire body can vibrate. The car, at the same time, wags, which is sometimes very well felt from the driver's seat.
The sign is also far from unambiguous, and may occur due to other reasons. For details, see the article on steering wheel vibration and wobble.
Smell of burnt pads
When jammed, the parts of the brake mechanism heat up to solid temperatures. First, you can smell the smell of burnt brake pads. If the problem is not addressed in a timely manner, then the leaking and evaporating brake fluid, as well as wheel bearing grease, will begin to stink later.
With a wedge of the brakes, a creak, whistle and even a crunch can be heard. When the constantly pressed brake pads wear down to the metal base, there is also a squeak. Often, a squeak is heard only when reversing, while there are no extraneous sounds when driving forward.
Car jerks while driving
If the brakes are not jammed tightly, which basically happens, then after a while the car starts to twitch, as if it were driving on slate. This happens, among other things, because the braking force is distributed unevenly across the disc.
How to make sure the brakes are stuck?
Hang the suspicious wheel on a jack (or all in turn), and spin it. Don't forget to release the handbrake and put the car in neutral. In good condition, the wheel should spin easily by hand and continue to rotate by inertia. If it rotates with difficulty or cannot be untwisted, the brakes are jammed.
Consequences of jammed car brakes
Knowing the possible consequences of a stuck brake will help you make the right decision and avoid additional costs. There are two options here - either do not continue driving and call a tow truck, or try to eliminate (weaken) the wedge in the field.
If the decision is made incorrectly, there may be the following consequences:
- Complete wear of the brake pads.
- Critical brake disc wear.
- Deformation of the brake disc.
- "Drainage" of the wheel bearing.
- Wheel slip.
- Increase in stopping distance.
- Loss of vehicle control.
Now a little more.
Complete wear of the brake pads
If you notice the symptoms listed above in a timely manner, and immediately take action, then you can even not buy new pads. They will be erased to zero, of course, not quickly. But when that happens, other problems can easily arise.
Critical brake disc wear
After the base material of the pads is completely worn out, metal will begin to rub on the smooth and even surface of the vise. The very first thing that will happen is deep scratches or uneven wear. It will have to be eliminated either by turning the brake discs, or by replacing them with new ones, which is no longer as cheap as a set of pads.
Brake disc warp
Occurs due to sudden changes in temperature. If a disc with jammed pads always cools down naturally, then nothing bad can happen. If you fly into a puddle with a hot disk, then deformations are almost inevitable. Even cracking and complete destruction of the part is possible. The same thing can happen if you try to cool the hot wheels by pouring water on them. Under no circumstances should this be done. Of course, with the exception of cases when the grease or rubber has already caught fire, which, although rare in ordinary life, but also happens.
"Drainage" of the wheel bearing
The heat from an overheated brake disc is inevitably transferred to the entire hub. This leads to overheating of the wheel bearings, due to which the lubricant from them first liquefies and flows out, and later completely evaporates. In the near future, this is guaranteed to end with the failure of the bearings and the corresponding symptoms.
Such an outcome is especially likely in winter when driving on packed snow or ice. When the wheel, in which the brake pads are wedged, hits a slippery one, it stops rotating. In some cases, this leads to a sudden skid of the rear axle or to the demolition of the front. Far from all drivers are capable of coping with an unexpected skid, and even pros can have problems at a decent speed.
Loss of vehicle control
If only one wheel is jammed, and the rest are slowing down, the car may suddenly throw to the side during braking, and it will stop only after it hits something (a pole, a fence, another car). On slippery surfaces, this can happen even with slight pressure on the brake pedal.
5 Causes of Car Brakes Jamming
In practice, there are a few more reasons. But those considered here are 90% of all cases.
Most likely causes:
- Handbrake malfunctions.
- Aggressive driving.
- The pads jammed in the guides.
- The movable part of the caliper is jammed.
- Stuck main piston.
These reasons are discussed in more detail below.
The operation of a handbrake is slightly different from the main brakes of a car. As a rule, it is completely mechanical. It is actuated by a lever in the cabin, the force from which is transmitted to the rear brake pads by means of a cable. The handbrake usually wedges only after the car has stood on it for a long time, and then they try to turn it off. The pads, at the same time, do not move away from the discs or drums, continuing to "hold the car by the ass."
The handbrake is usually buggy for one of the following reasons:
- The cable wedged - dirt got inside, rust formed, or the cable threads partially burst, and cling to the braid.
- The return spring does not work - there are several reasons, but the main one is natural wear. The spring is weakened, and cannot take the pads to their original position.
- The pads “got stuck” - usually the result of movement on a forgotten handbrake, when the thermal deformation of the return mechanism occurs, and it no longer works.
- The pads are frozen - it happens all the time in winter or autumn with the onset of the first frost, when the car has been on the handbrake for a long time, and water has got into the mechanism before that.
If the problem is in the handbrake, then its elimination comes down to cleaning/lubricating or replacing the listed parts. Frozen pads can be easily warmed up with a regular household hair dryer. Again, watering the wheels with water (in this case, boiling water) is not worth it.
Aggressive driving is inevitably accompanied by frequent and intense braking, as a result of which the brake system heats up and does not have time to cool down. Due to overheating, thermal deformation of the parts occurs, which leads to a wedge. It's also worth noting that you don't have to drive aggressively to overheat your brakes. The usual, but long-term traffic on a city road overloaded with traffic is enough. For example, in traffic jams, the speeds are low, the brakes are practically not blown by the oncoming air flow, but are used very often.
Pads jammed in guides
Brake pads don't stick very often. If this happens, then the reason for this is the poor quality of parts, distortion, size mismatch, destruction. You can see all these problems with the naked eye if you look at the caliper from the end (with the rim removed).
Jammed movable part of the caliper
In brake mechanisms with one main piston and two guides, the latter may jam. This happens for various reasons. Mainly due to the fact that dirt/dust gets into the assembly, or due to systematic overheating, the lubricant evaporates. Rust, by the way, has not been canceled either. In any case, these problems lead to the fact that, with a completely serviceable drive mechanism, the caliper itself is immobilized, and the pads cannot return to their original position.
The pads themselves also move inside the caliper along their guides. Due to the fact that the wheels are operated in rather harsh conditions (dust, dirt, water), corrosion forms on the guides, which does not allow the pads to move freely. Since the force with which a serviceable piston presses on the pads is decent, it jams them more often in a position pressed against the disc.
Stuck main piston
The brake piston is the cause of stuck pads in 80% of cases. So, this is the most common problem. The piston is a high-precision part made of durable metal. Its surface should be polished to a shine. The piston moves in its holder and is actuated by the pressure of the brake fluid. To prevent the assembly from becoming dirty, it is protected by an elastic boot, under which there is a lubricant.
Most often, the root cause of a piston wedge is precisely a damaged or worn anther. When it cracks, tears, or simply tans in the cold due to poor quality or “old age”, dust, dirt and moisture get on the polished surface of the piston. As a result, corrosion develops, which violates the ideal geometry of parts. As a rule, the piston most often jams in the extended position and does not return back. Accordingly, the brake pads remain constantly pressed against the disc, which causes the symptoms discussed above.
Jammed brakes: what to do?
If the hand brake was not the cause of the wedge, then the problem first begins to appear right while driving. The above symptoms can manifest themselves in completely different ways. In some cases, the wedge is not even noticed at first, and they continue to ride with it for a long time. And it also happens that the car at a decent speed suddenly begins to behave inappropriately - vibrations appear, a burning smell is heard in the cabin, the car twitches and wags.
Of course, the first thing to do in such cases is to stop the car. Next, you should find out if the problem is in the brakes, and on which of the wheels it arose. To do this, get out of the car and compare the degree of heating of the rims. Remember that touching hot discs is hazardous to health. Estimate heating remotely.
If one of the wheels is really hotter than the others, smoke or steam is observed, you must wait until the parts have cooled to safe temperatures. It should be said that all this does not cool down quickly, especially if it is summer and heat outside. In any case, climbing to the hot wheel is not worth it, since even removing it will be difficult. Not to mention burns.
When the wheel is cool, jack it up, remove the bolts (or nuts) and remove it. Carefully inspect the brake mechanism, paying attention to the caliper, brake pads and brake disc. To see the clamped pads, you need to look at the caliper from the end. At the same time, you can see the degree and uniformity of their wear. Usually, if the brakes have been wedged for a long time, this is clearly visible just by the pads.
If possible, the jamming of the brakes can be eliminated temporarily. This will allow you to safely get to the house or service station. How to do it?
Forcibly spread the brake pads
You can try to do this with a screwdriver or something that looks like a hammer. Strongly knocking on the caliper and picking the pads is not worth it, as these are rather fragile parts. You can help yourself with an aerosol lubricant such as "WD" (after applying it, please note that this wheel will not brake at all for some time).
If the pads managed to be separated, try to scroll the brake disc - it should rotate easily, but with a slight interference. If so, start the engine and depress the brake pedal, then check to see if the pads are stuck again. By lubricating the mechanism and repeating the procedure described, you can temporarily revive the brakes and drive home safely. If the pads cannot be wedged in this way, proceed to the second method.
Remove the caliper
This is a more radical method, which is advisable to resort to only when it is not possible to use the services of a tow truck, and the pads do not lend themselves in any way. The method consists in the fact that the caliper is completely removed, and, together with a flexible pipe for brake fluid, is tied to the shock absorber strut so that later it does not interfere with the wheel from rotating.
When resorting to this method, keep in mind that the brake piston that presses on the pads must be fixed somehow. Otherwise, the first time you press the brake pedal, it can be squeezed out, which will lead to leakage of brake fluid from the system and a complete failure of the brakes. To fix the piston in the field, you can insert the removed pads into the caliper and tie the whole sandwich with wire. When braking, the piston will simply rest against the pads, and nothing bad will happen.
If weather conditions are favorable, then you can also try to develop a jammed mechanism in the field. However, in most cases, without tools, pushing the piston back in will be very difficult, if not impossible. Therefore, if it does not work out, it is better to leave everything as it is, without resorting to brute force and the use of a percussion instrument.
In order not to encounter the described problem in the future, the brake system must be regularly looked after. As a rule, for this it is enough to remove all calipers at least once a year, check the condition of the pistons, anthers and the presence of lubrication. Along the way, the degree of wear of the pads and the output on the disks are estimated. It is also important to change the brake fluid in a timely manner. According to the regulations, this is usually recommended to be done every two years. The fluid must be changed because water accumulates in it over time, due to which corrosion of the brake pistons occurs.