Last Updated on January 29, 2024 by Pittalks
Brake bleeding is a crucial maintenance process that ensures your vehicle’s braking system is functioning correctly. However, there are instances when no brake fluid comes out of the rear brakes during bleeding, indicating a problem. This issue can be caused by various factors, including using the wrong bleeding procedure, faulty proportional valve, or a faulty bleed screw.
In this article, we will provide you with a comprehensive guide on how to brake bleed and the different methods of bleeding brakes. We will also explore the reasons why brakes cannot bleed and, most importantly, why there is no brake fluid to the rear brake when bleeding. By the end of this article, you will have a better understanding of brake bleeding and the steps required to fix any issues that may arise.
Wrong procedure – Methods of brake bleeding
Bleeding the brakes is a crucial maintenance task that ensures your vehicle’s braking system is working correctly. However, if not done correctly, the procedure can lead to disastrous outcomes on the road. There are five methods of bleeding the brakes, which include the pump and hold method, pressure method, vacuum method, reverse method, and gravity method.
Solution:
If you have the correct procedure, then brake bleeding won’t cause you any problems at all. Here are some things to keep in mind to ensure that you’re following the correct procedure:
- Choose the right method: Choose the method that works best for your vehicle. If you’re not sure which method to use, consult your vehicle’s owner manual or a professional mechanic.
- Use the right equipment: Using the right equipment is essential to ensure that the bleeding process is successful. Some of the equipment needed for brake bleeding include a brake fluid tester, a brake bleeding kit, and a vacuum pump.
- Follow the correct procedure: Follow the correct procedure for the method you’ve chosen. For example, if you’re using the pump and hold method, one person should step on the brake pedal while the other individual opens one bleed screw at a time to let the air escape.
- Check for air bubbles: Check for air bubbles in the brake fluid by looking for bubbles in the brake fluid reservoir or at the bleeder valve. If you see air bubbles, repeat the bleeding process until the brake fluid is free of air bubbles.
- Check the brake fluid level: Check the brake fluid level regularly during the bleeding process to ensure that the brake fluid doesn’t run out.
By following these steps, you can ensure that you’re following the correct procedure for brake bleeding. Additionally, you can use a DIY kit to help you avoid getting any air bubbles in the system again. An excellent example of this is using a bottle whose bottle cap has an opening and a small hose that goes all the way down to the bottom. This setup is simple and easy, allowing you to empty the fluid into the bottle without any air bubbles forming in the system again.
The Proportional Valve
Proportional valves are devices that you can use to reduce the brake fluid pressure that goes to the rear brakes. If the proportional valve fails, there will be a problem with bleeding the rear brakes. The valve will not affect the front brakes if it fails, only the rear ones. Which is to say, if your front brakes are bleeding correctly, but the rear brakes aren’t, then your problem lies with the proportional valve.
Solution:
If you are experiencing issues with bleeding the rear brakes and the front brakes are working correctly, then the problem may be with the proportional valve. Proportional valves are responsible for reducing the brake fluid pressure that goes to the rear brakes.
To diagnose the proportional valve, you must disconnect it from the system and use a sprayer to pass fluid through. Fill the sprayer with a clean generic fluid that will be squirted through the four openings of the valve. If the fluid passes through all the openings, then the issue isn’t the proportional valve. However, if the fluid fails to pass through one opening, it indicates that you need a replacement part.
It’s important to note that if the proportional valve fails, it will only affect the rear brakes and not the front ones. Therefore, if the front brakes are bleeding correctly, but the rear brakes aren’t, then the problem lies with the proportional valve. You can purchase a suitable replacement valve from your local mechanic shop or search online.
Something wrong happened to Bleed Screws
The bleed screws are located on the exterior of the brake caliper’s fluid chamber. Their positions are on the wheel brake cylinders. This is the screw you open to bleed the brake fluid out of the braking system.
The location of the bleed screws makes it challenging to prolong their longevity. The screws are hollow and can be easily corrosive from exposure to their surrounding environments. They are exposed to harsh environments such as moisture from the road, heat from the caliper, and winter road salts.
The exposure can cause the bleed screws to leak, block, and rust. Moreover, the screws can get damaged after a previous repair that wasn’t done properly and carefully.
Solution:
When there are issues with the bleed screws, it is important to take action to fix them. Here are some solutions to common issues with bleed screws:
- Check for blockages or leaks in the seat of the screw. If there are any, it may be time to find replacement parts.
- If the bleed screw is damaged, it will need to be replaced. This can be done by removing the old screw and installing a new one.
- If the bleed screw is corroded, it may need to be cleaned or replaced. To clean the screw, use a wire brush to remove any corrosion. If the screw is beyond repair, it will need to be replaced.
It is important to note that bleed screws are located in harsh environments and can easily become corroded or damaged. Regular maintenance and inspection of the brake system can help prevent issues with bleed screws.
Something wrong happened to Flex Hose
The flex hose is a flexible hose that we use to carry fluid to the dynamic brake caliper. Like the bleed screws, these flex hoses are exposed to tough environments that can accelerate their age. Over time, the flex hose will either block, start leaking fluid, get corroded, or have its internal walls rot. All of these will result in the contamination of the brake fluid.
Solution:
If there is a problem with the flex hose, it is essential to analyze it carefully to identify the issue. The following are some of the common problems that can occur with the flex hose:
Leaks
The flex hose can start leaking fluid due to its age or exposure to harsh environments. The brake fluid contamination can lead to brake failure, which can be dangerous. It is crucial to check the internal and external walls of the hose for any leaks.
Blockage
Over time, the flex hose can become blocked due to the accumulation of debris or corrosion. If there is a bulge in the hose, it is an indication of blockage. Applying pressure on the brake pedal to pump brake fluid through the flex hose can help identify the blockage.
Corrosion
The flex hose can become corroded over time due to exposure to harsh environments. Corrosion can weaken the hose, leading to brake fluid contamination. It is essential to check the overall condition of the hose for any signs of corrosion.
Rotted Internal Walls
The internal walls of the flex hose can rot due to the age of the hose. Rotted internal walls can lead to brake fluid contamination and brake failure. It is crucial to check the internal walls of the hose carefully.
To fix any of these problems, it is necessary to replace the flex hose. A new flex hose will ensure that the brake fluid is clean and that the brakes are functioning correctly.
Something wrong happened to Caliper
When it comes to brake bleeding issues, one of the possible causes is an incorrectly fitted caliper. Calipers are sensitive to direction, which means that they are made to be put in specific locations. A right-hand caliper should never be placed on the left side. They have labels with the letter ‘L’ and ‘R’ to denote where you should place them.
The fastest way to know if you placed the calipers incorrectly is to look at the position of the bleed screw. It should be towards the top. The idea behind the top-positioning of the screw is based on the fact that trapped air bubbles tend to flow to the highest part of the caliper.
Solution:
If you suspect that the caliper is fitted incorrectly, proceed to check the position of the bleed screw. If it is not towards the top, it is likely that the caliper is incorrectly fitted. Here are the steps to fix the issue:
- Change the sides respectively, making sure you do not mix them.
- Bleed the brakes again to ensure that all air bubbles have been removed.
- Test the brakes to ensure that they are working correctly.
It is important to note that caliper issues such as leaking seals, seized pistons, seized pins, and sliding brake caliper pins can also affect the braking system, but they do not cause brake bleeding issues. If you suspect that your braking issues are caused by these caliper faults, it is recommended to take your vehicle to a qualified mechanic for inspection and repair.
Overall, it is important to ensure that the caliper is correctly fitted to prevent brake bleeding issues and to ensure that the braking system is working correctly.
Blocked/Leaking Pipe or Air Bubbles in the Pipe.
Blockages are regular; they happen all the time. The cause are dust, debris, inclusions, and improper braking fluid.
Solution:
To check for any blocks and leaks, perform the same procedure used to check the flex hose. If the brake pedal is pressed and a bulge is noticed in the pipes, a block is the main issue. The pump and hold method is the best procedure for this. Blockages are regular and can be caused by dust, debris, inclusions, and improper brake fluid. Leaking brake fluid can be caused by blocked pipes or air bubbles in the lines. Here are the causes and fixes for this common issue:
- Blocked brake line will prevent the free flow of fluid
- Air bubbles in the brake lines can cause a decrease in hydraulic pressure and braking efficiency
- Problems with the bleed screws can also cause a lack of fluid during bleeding
If the brake line is blocked, the brake fluid cannot reach the calipers. It is crucial to perform brake bleeding to avoid squeaky noises and ensure effective and safe braking performance.
Crud and Corrosion build up in the lower Halves of the Bores.
Corrosion on the braking disks or drums can increase the noise and vibrations from the braking system. Moreover, it will inevitably reduce the braking efficiency of your system. If left unchecked, it can lead to disastrous damages on the discs and pads due to corrosion adhesion.
Moreover, corrosions on bores and pipes lead to holes and leaks. This is what causes the rear brakes to not bleed or receive enough pressure from the braking system.
Solution:
When there is crud and corrosion build-up in the lower halves of the bores, it can cause the rear brakes to not bleed or receive enough pressure from the braking system. This can lead to disastrous damages on the discs and pads due to corrosion adhesion. It is, therefore, important to take preventive measures to avoid such scenarios.
The solution for this cause is to replace the entire part as soon as possible. Check for any spots and leaks before proceeding to buy new components. This will help to ensure that the new components are not affected by any existing corrosion or crud. Additionally, it will help to ensure that the braking system is functioning optimally and is safe for use.
In conclusion, it is important to regularly check for any signs of crud and corrosion build-up in the lower halves of the bores. This will help to ensure that the braking system is functioning optimally and is safe for use.
Conclusion
Regular maintenance and proper brake bleeding techniques can prevent issues such as a spongy brake pedal. It is essential to check the brake fluid during maintenance schedules and seek professional help if necessary. Brake bleeding is a simple process that becomes easier with experience. It is important to follow the correct procedure to avoid damaging vital components. By taking these precautions, one can save time and money and ensure a safe driving experience.
FAQs
Can I just bleed my rear brakes, or should I Bleed All 4 Brakes?
The answer to this question depends on the type of brake system that your vehicle has. Most modern vehicles come with independent brake lines that allow you to bleed one brake caliper without affecting the others. However, you must ensure that the brake fluid level isn’t below the level mark in the reservoir. If it is, you will need to bleed all four brakes to achieve the desired results.
Can I change brake fluid without bleeding?
Yes, you can change brake fluid without bleeding by using a pump. Connect the pump to the master cylinder and suck the fluid out of it. However, be careful to ensure that the system doesn’t expose to air when removing the brake fluid.
It seems the brakes still spongy after bleeding?
If you have correctly bled your system, but the brakes still feel spongy, then the problem may lie in a faulty component. The faulty component issues may include a malfunction in the ABS, leaks in the wheel cylinders, a worn-out master cylinder, leaking disk brake calipers, and damaged brake lines.
Can I bleed brakes with the engine running?
You can bleed brakes with the engine off when the goal is to bleed the base brakes that do not need a pump. However, if you also want to bleed the ABS, you would need to have the pump run, which requires a running engine.
Will brakes eventually bleed themselves?
Brakes will not bleed themselves under any circumstance. You will have to manually use any of the methods mentioned above to bleed the brakes.
Can you brake without brake fluid?
No, brakes cannot function without brake fluid. Brake fluid is an incompressible liquid that provides a reliable link between the brake pedal and caliper. This secure connection helps in transferring the hydraulic pressure efficiently throughout the system. Without brake fluid, the braking system will not work, and the vehicle will not stop.
Wrapping Up
In summary, it is essential to understand the brake system in your vehicle to know whether you can bleed one brake caliper or should bleed all four brakes. You can change brake fluid without bleeding by using a pump, but be careful not to expose the system to air. If the brakes still feel spongy after bleeding, there may be a faulty component that needs fixing. Brakes cannot bleed themselves, and brake fluid is necessary for the braking system to function.
