Much has been said about the importance of uninterrupted operation of all elements responsible for applying the brake. This article will talk about repairing the components of the caliper: the piston (cylinder), guides and replacing their boot - with your own hands, you can also learn about this clearly from the attached video.
To fully understand how to easily repair and replace these parts, it is worth understanding the structure of the front and rear calipers and the reasons for their failure, and what repair kit may be required for this.
The design of this brake element
There are two types of disc calipers - front and rear, their design and repair method are slightly different, but their main elements are the same:
- The housing in which the piston (cylinder) is mounted.
- Bypass valve.
- Sealing ring.
- Piston (cylinder).
- Cylinder boot.
- Retaining ring.
- Frame.
- Pressure bar.
- Pads.
- Guide boot.
- Guides.
- 14. Fastening bolt.
- Brake hose.
The difference between the rear disc caliper is the presence of a parking brake.
Therefore, the piston (4) has a special thread through which it is screwed onto the parking brake rod (1). Thanks to this, it can operate under the influence of two drives - mechanical (parking) and hydraulic.
Causes of failure
The caliper as an element of disc brakes is subjected to significant temperature loads, as well as exposure to external adverse factors: dirt, dust, moisture, chemicals. All this happens due to the fact that his device does not allow him to be protected from these negative phenomena. If there is significant overheating, as well as if the boot ruptures, the lubrication of the guides may disappear.
Improper maintenance of the guides, in which some craftsmen manage to stuff inappropriate lubricant into their boots: graphite or similar, leads to their swelling and souring, after which they jam or knock when suddenly activated.
A rupture of the piston boot causes dirt and moisture to enter it. After which it stops working - it starts to jam or, conversely, knock.
Deformation of the sealing ring contributes to brake fluid leakage and oiling of the pads.
Some general information
Before starting work, you need to decide what exactly the problem is. The thing is that humming and creaking during braking can occur for several trivial reasons. As a rule, this is critical wear of the part or a complete or partial lack of lubrication under the boot. This work can be called easy in terms of complexity, the only problem may arise if the anthers are stuck, but this can be solved quite quickly. To begin with, it is advisable to install the vehicle on an inspection hole or use a lift. In most cases, a regular jack is sufficient. We remove the wheel and see our actual problem area, which we will have to work with in the near future. If everything is very dirty and nothing is clear, then we take a metal brush in our hands and carefully clean everything. Be careful not to damage the boots, as they are made of thin rubber.
Repair kit
Replacing a caliper is a drastic measure; often you can limit yourself to repairing and replacing its components. Basically, the standard repair kit includes rubber elements:
- cuffs,
- anthers,
- protective rubber bands of the fitting,
- piston sealing rings.
But depending on the necessary repairs, they may include:
- retaining rings,
- clamping brackets,
- guides,
- directly the pistons themselves.
Thanks to the repair kit, you can significantly save and improve the operation of this brake system unit.
Signs of trouble
The breakdown of the caliper components and their impending repair can be understood by some signs that occur during braking:
- The car pulls and pulls to the side when braking.
- It feels like when braking you have to put more force on the pedal or, conversely, less.
- The brakes rattle or knock when driving over bumps or when stopping.
- The brakes are jamming, which will be indicated by possible skidding.
- The appearance of brake fluid leaks on the wheel.
- Feedback in the pedal, expressed in a strong pulsation when pressing the brake.
If these symptoms appear, you should not delay repairing faulty caliper elements. You must first figure out why this happened and make repairs immediately. You can learn more about the signs and causes in the attached videos at the end of the article.
If the brakes rattle
This type of brake has pressure springs or floating calipers.
They are responsible for securing the pads to the caliper body. The reason for their failure is metal fatigue or poor quality. As a result, they lose their elasticity and stop pressing the pads against the body. Because of this, the pads rattle at the slightest passage of irregularities and may come into uneven contact with the disc, which will lead to the appearance of a shoulder or grooves on it. Also in this case, the staples themselves may rattle.
What should you do when your brake calipers or pads rattle? If it is not possible to replace them, then you should try to loosen them with your own hands using pliers to make them more rigid. To do this, you need to pull them out of their seats, unclench them and insert them into place, after which they will stop rattling for a while.
Rear caliper repair
Actually, let's look at the process using the example of the rear caliper of a Chevrolet Lacetti
The first step is to open the brake reservoir cap, place a bag on the neck and screw the cap into place.
This is necessary in order to limit the access of air into the tank. This will prevent the brake fluid from quickly flowing out of the hose when we unscrew it.
Jack up the car and remove the wheel.
Use a metal brush to clean everything that can be cleaned.
After this, apply penetrating lubricant to the brake hose bolt.
We wait a little and try to unscrew the bolt with a 12 mm wrench.
If it's good, that's good. And if it doesn’t work out, then that’s bad and I don’t envy you.
We wrap the unscrewed hose into a “finger” from a rubber glove and wrap it with wire. During repairs, these measures will be enough to avoid brake fluid leakage.
There are craftsmen who clamp the brake hose for these purposes, but I don’t want to do that. Who knows what will happen to this hose later. It's better not to take risks.
We remove the unscrewed bolt to the side and at the same time try not to lose the copper sealing rings. There are two of them.
That's it, the caliper is disconnected from the system and we now need to remove the caliper cylinder itself. To do this, use the same 12 mm wrench to unscrew the lower bolt of its fastening.
After this, lift the cylinder up. If it is very jammed, then you can help yourself with a large screwdriver or a pry bar.
We take it out together with the upper guide. We look into the hole where the brake hose was previously screwed in and see the back of the piston.
Using something, we need to squeeze out this very piston through this hole.
If it’s really tight, then you can help a little with a hammer, or better yet, with a vice.
After the piston has come out, we assess the situation. If the piston is full of holes and pockets of corrosion, then it is better to replace it. If the corrosion is not significant, then you can polish it with felt and Goya paste. In my case, there were pockets of corrosion, but it was not possible to purchase a new piston. Therefore, after a little polishing, I left it to serve further.
We clean and wash all the grooves in the cylinder.
The far groove is the seat of the sealing collar, and the near one is the boot
After this, lubricate the cuff groove and the cuff itself with piston lubricant. The groove must be lubricated to avoid corrosion under the cuff. Install the cuff into the cylinder. This is done quickly and easily.
Now the most important thing. It is necessary to put on the piston boot and insert the piston itself. To do this, lubricate the piston with the same grease and put the boot on the piston from the back side.
I was filming a video and forgot to take a photo. That's why I inserted a still from the video. It looks bad, but the essence, I think, is clear. The part of the boot that is inserted into the cylinder groove hangs slightly from the piston.
Now, when installing the piston, the boot will fall into its groove in the cylinder. In this case, the piston can be rotated slightly so that the boot placed on it falls into its groove completely. If the boot is bitten a little, then you can help it get into the groove with a screwdriver. But be careful not to tear the boot.
There is nothing complicated. You can easily figure out the place.
Now you can push a little more grease under the boot. This can be done more conveniently using a syringe.
Squeeze the lubricant into the syringe.
We push the piston into the cylinder and excess lubricant will be squeezed out from under the boot.
The piston should move easily and move with bare hands. If it doesn’t move, it means something went wrong or you didn’t eat enough porridge as a child. If the problem is a mess, then you can use this device to recess the piston.
Now you need to wash the seats of the guide pins.
If there is severe contamination, then it will be more convenient to dismantle the whole thing and wash it on the table.
After that, apply a little grease for the guides there. You can insert the guide and use rotational movements to evenly distribute the lubricant.
We install the anthers so that they fit into their grooves. And insert the bottom guide
Clean the pad guides and lubricate them with a thin layer of high-temperature grease
We lubricate the ends of the pads with the same grease.
We do the same with the back side of the block.
It is better not to lubricate the second pad, which faces the piston, so that the lubricant does not get on the piston boot.
We install the pads in place, first making sure that the lubricant does not get on the working area of the pads.
Lubricate the second guide that remains on the cylinder
And install the cylinder in place.
Screw on the brake hose. We remove the bag from the brake reservoir, but do not screw the lid on yet.
We unscrew the bleeder fitting and wait for brake fluid to flow out of it.
It is located at the top of the cylinder and the liquid, filling the volume of the cylinder, will displace the air from it.
After the liquid begins to come out, you can tighten the fitting. To ensure that there is no air in the system, you can have an assistant press the brake pedal several times and bleed the system. If your assistant cleaned the ram properly, ask him not to touch the steering wheel with his hands while pumping the brakes.
That's all you need to do to repair the caliper yourself.
1306 words written... In general, restoring a caliper is much faster than writing about it.
What happens if you don’t service the caliper and don’t notice a worn boot in time.
Don't forget to check the brake fluid level and tighten the reservoir cap. Before leaving, press the brake pedal several times until the piston reaches its working position.
The piston (cylinder) is faulty
Poor quality of brake fluid, the appearance of rust on the surface when the boot of at least one piston (cylinder) ruptures or as a result of prolonged downtime of the machine entails its partial jamming.
This will initially be heard when its operation is delayed, when the pads begin to knock on the disc. In order to make the repair yourself in this case, you need to disassemble the caliper and pull out the rusty piston; this must be done after the guides have been unscrewed and the boot and retaining ring have been removed.
If the cylinder still moves even slightly, you can squeeze it out using a compressor by inserting a hose into the hole for supplying brake fluid. This can also be done without first disconnecting the housing from the brake system; you just need to press the pedal, after which the created pressure will squeeze the cylinder out of its seat. If it is tightly jammed, then a preventive measure can be soaking it in gasoline and other similar liquid.
It is worth considering that the rear caliper piston cannot be removed, but is simply unscrewed along the threads with pliers or a similar tool. After this, you need to wash the cylinder seat and clean it of dirt and rust. It is also worth doing with the piston (cylinder) itself. Next you need to insert the cylinder into place. It would be useful to replace its boot with a new one during assembly. You can see this in more detail in the attached video.
DIY caliper repair
With the end of the cold weather, patience also ended. I couldn’t stand the smell of burnt dust, the whistle and stench of overheated pads from jammed caliper cylinders and the “nodding” when stopping, so we bought everything we needed and went to my father-in-law’s garage (I did the front and back with a break of a week). Unfortunately, there are no photographs, because I was very passionate about the process. What you need: 1. Rem. sets of calipers 2. Brake fluid Castrol DOT-4 1 3. Construction gloves 2 pairs 50 rubles, rubber gloves 4. GOI paste 5. A lot of unnecessary lint-free rags. 6. Plumbing thread. 7. Half a 5 liter bottle 8. Rust converter 9. Medical dropper 10. Medical syringe 20 cc
The first step was to disassemble the problematic right rear caliper. 1. Jack up and remove the wheel. 2. Remove the handbrake mechanism. To do this, we bend and pull out the spring (although I am not small in caliber, I am also not a master of sports in arm wrestling, I was able to do this with my fingers to my surprise), then unscrew the bolt securing the swing and disconnect the cable (I immediately discovered the reason for the handbrake freezing in winter - a torn boot on a cable, this still needs to be sorted out, not sold separately, only assembled with a cable, will have to be farmed). 3. Next, loosen the bolt securing the hose to the caliper body (after removing the caliper, this will be more difficult to do). 4. Next, we unscrew the bolt that secures the caliper and fold it back, helping ourselves with a screwdriver and swear words, because the pads are jammed by the cylinder. We remove it from the guide and see the reason - a torn boot on the cylinder. 6. Place a 5-liter bottle sawn in half under the scene of action to avoid clogging everything with brake fluid. 5. Next, you can try to unscrew the brake cylinder with pliers, inserting it into the groove for the special device counterclockwise (or with a mythical special device that could not be found in the city), but I did it easier - I drove my father-in-law into the car, he started it and, progressively, without quickly pressing the brake pedal has been pressed out by a cylinder from the caliper body, but it is still under the boot. 6. Next, unscrew the bolt securing the hose and try not to lose the two copper sealing washers. We wrap the bolt with plumbing thread and insert it into the coupling with a hose to prevent brake fluid leakage. PS It is better to remove the pads with the springs and put them in a secluded place so as not to lose the latter, it will be very difficult to then look for steel wire to make the springs. 7. Now we have the caliper with the almost disconnected cylinder at our disposal, we can work on it. We take a screwdriver with a small, non-sharp tip and look for a locking open ring above the boot, pry up the end and carefully remove it. Then we remove the stuck boot and cylinder. Next, the cause of the jamming was visible - the internal cradle where the edges of the boot are inserted, as well as the edges of the hole for the piston, as well as part of the piston, are covered with corrosion. There is nothing to do, we begin a long, stubborn and inconvenient cleaning of corrosion using rags, rubber gloves, a rust converter and in non-working places (not the cylinder and not the hole under its walls) - with a screwdriver to remove the converted corrosion. Next, we thoroughly rinse everything with the old drained brake fluid and wipe it off. It's time for the top hat. We rub the rags with GOI paste, firmly clamp the cylinder in a vice and begin polishing the surface free of corrosion. After some time, the cylinder shone like a cat's bells and became much smoother. We change the sealing collar in the caliper body (the old one seemed to be good, well, since we took it apart...), lubricating it on all sides with red grease from the repair kit (the Chinese Germans are great - they put enough grease and 2 types, red and yellow, red as times for internal parts). We lubricate the cylinder itself and the boot with it on all sides. We put the boot on the cylinder (just throw it on), insert the cylinder into the caliper, take the pliers and begin to twist the cylinder into the body clockwise with moderate dosing of pressure and rotation. We are approaching the end of the year - carefully use a screwdriver to tuck the edge of the boot into the groove, take the open ring and no less carefully place it in the groove where the edges of the boot have just been pushed. Apply yellow grease to the caliper fixing bolts and reassemble in reverse order. 8. Afterwards, repeat the operation on the left caliper. 9. After completing the repair of the calipers, it is necessary to bleed the brake system to remove all the air. With the help of my father-in-law, we pump all the wheels one by one (even the front ones, which I only got to in a week). To do this, remove the cap from the bleeder fitting, place the key on the 8th ring side, and put a hose on top with a rubber band from the dropper (fits perfectly). On command, the Father-in-law pumps up the pressure with the brake pedal until it becomes stiff, and holds his foot in this position. At this moment I open the fitting with a key, bleed air and liquid and control the air outlet through the transparent dropper hose. As soon as the brake pedal goes to the floor, he commands, I close the fitting, after which he releases the pedal. Next, we repeat the operation, and every 2 such times we run to add brake fluid to the reservoir so that more than a quarter does not go away, as recommended. We repeat until liquid comes out without air, make another control pass, and tighten the fitting. We carry out the operation on all 4 wheels in turn from the closest to the farthest wheel from the place where the hose is disconnected. After the operation was completed, it was already evening. But you need to check it. I sit down, drive out onto the alley of the garage cooperative, accelerate to 20, press the pedal, it’s soft (It brakes well, but there is a treacherous idle to the point where it starts to grip confidently. The cylinder doesn’t jam, there’s no stink, it doesn’t bite. A profit is made, but and I got an inconvenience in the form of a soft pedal (I thought about the air in the system, but after the second pumping after repairing the front calipers, which I will write about later, the situation remained the same).
This concluded the first day of the struggle. Since I did everything carefully and slowly, and for the first time, it took about 6 hours. To be continued.
Continuation. I drove for a week with the “new brakes”, gradually got used to it, but still anticipating the return of the old harsh, upsetting ones, I planned Sunday to work on the front pair of calipers. Started. 1. Jacked it up and removed the wheel
front caliper, top view
2. Loosen bolt 1 in the assembled state with a 10mm head 3. Remove the cap, then use a 8mm L-shaped hexagon (the set was purchased a long time ago, because it’s unlikely to be unscrewed with an ordinary bit from a screwdriver), feel for the groove of the sleeve and unscrew it (it was unscrewed without problems because earlier after replacing the pads, everything was lubricated with lithol - of course it’s not high-temperature shit, but it did its job). 4. Next you will have to unscrew bolt 2 completely. Do not lose the 2 copper washers of the gasket. 5. We plug the hose coupling with a bolt wrapped in plumbing thread, tilt the caliper and remove it from the lower guide. It will not work without disconnecting the hose, because it is short. 6. Return the hose to its place, tighten the bolt, and hold the caliper in your hand. 7. The father-in-law starts the car, carefully progressively presses the brake so that the cylinder comes out of the caliper body. 8. The cylinder comes out, unscrew bolt 2, equip it with plumbing thread, and lock the hose coupling. 9. Now you can work. Unlike the rear caliper, the front caliper does not have a ring that pushes the boot apart; it can be removed without effort. The cylinder itself does not have grooves for screwing in/unscrewing; it moves on its own without threads. As a result, we see the following: On the caliper
Inside the caliper
Corrosion in the groove for the boot 1 (the boot was torn), corrosion on the walls of the hole along which the cylinder 2 moves, and a worn cuff 3.
The cylinder itself is in good condition, slight corrosion in the groove for the boot 1 and on the body itself 2
front brake cylinder
I treat corrosion with a rust converter. I clean the groove for the boot (non-working surface) with a screwdriver suitable for the width of the tip, and wash it with old brake fluid. I polish the cylinder body with a rag coated with GOI paste until the corrosion spots are reduced to a minimum. I am changing the guide boots from the repair belt. kit, lubricating them with yellow grease (the Chinese Germans squeezed a second bag of yellow grease into the front repair kit, unlike the rear one there is only one). I clean and treat the corrosion in places 1 and 2 in the caliper body, wash it with the old brake fluid, change the sealing collar 3, having previously lubricated it with red grease from the belt. set. Lubricate the cylinder boot and the cylinder itself with red grease. Next we assemble: In order not to repeat my mistake (I wanted to insert the cylinder as in the back, first - then put on the boot - it didn’t work - in the end I ran to squeeze it out again through the hose) put the boot on the end of the cylinder (number 2 in the photo), tuck the boot into the groove carefully so as not to jump off the cylinder and slowly move the cylinder inside. Next, without much effort, resting your fingers on the edge of the cylinder, we gently press it into the caliper body without distortion. Profit. PS. Don't forget that the brake hose is still short, so we lubricate the guide and bushing with yellow grease from the belt. kit and install the caliper in place, tighten the bushing, then connect hose 2 from the first photo into place (do not forget about the copper washers). Then we do the same on the left side. Upon completion, we bleed the brake system through fitting 3 in the first photo (all the same with spare parts from the dropper, as in the first part of the post). PPS Unfortunately, it won’t be possible to bleed the rear wheels from the pit, well, this is the design, everything is closed with levers, so you still have to remove the wheels one by one. The procedure, like the back part, took a leisurely 6 hours. After bleeding the system, I go for a check. The whistle disappeared, but the brake was still soft. Air? who knows, they are not professionals, of course, but they have pumped up more than one car, this has never happened. The soured cylinder is no longer soured and has a greater stroke than before, which is responsible for the greater useless stroke of the brake pedal? Logical, but idk. In general, now this is mystery No. 1.
Guide faulty
The main problem if the brake does not work can be jamming and souring of the caliper guides.
Repairing this malfunction with your own hands will not be difficult. By the way, in this case there is no difference when disassembling both the front and rear calipers. To do this, you need to unscrew and pull out both guides. Clean them from dirt or poor-quality lubricant, remove and replace the torn boots with new ones, after filling them with special grease for calipers.
Then put them in place, insert and screw the guides back. Then you should try how freely the pressure bar moves along them. This can be seen visually in the attached video at the end of the article.
We should not forget about the housing of this brake element. If significant rust, dents, sagging or other mechanical damage is found on it, it should be replaced completely.
If the repair had to be done on a removed caliper, then after installing it in place, the brake system should be bled.
Related publications:
- When should you replace brake pads?
- Why do brake pads squeak and whistle when braking?
- Types of brake pad wear sensors and how they work
- How to change brake fluid?
- Do-it-yourself grooving of brake discs, can it be done without removal or is it still necessary to remove it?
Detailed instructions for repairing calipers
The most common cause of brake caliper failure is its souring and subsequent jamming.
If the caliper is regularly maintained and lubricated, it can last for decades without any repairs. But the main thing is to choose the right lubricants!
If interested, read about choosing lubricants. In this article we will work with them, but I will not spend letters in this article describing these lubricants.
Caliper repairs can be divided into three categories:
- Mandatory caliper lubrication when replacing pads
- Reanimation of the caliper if the wheel is already heating up
- Complete disassembly of the caliper and replacement of worn elements
The first two categories can be viewed via the links. And in this article we will look at the third category, when it is too late to drink Borjomi and surgical intervention is necessary.
Most often, the reasons for complete caliper failure are two things:
- The caliper has never been lubricated or serviced. As a result, the piston and guides were severely corroded.
- The caliper was not lubricated with what was needed. As a result, the lubricant turned into plasticine or powder, and the anthers and cuff mercilessly swollen.
In these two cases, you can no longer get by with half measures and you will have to do the job thoroughly.
