Did you know it is recommended to change your car’s brake fluid after four to five years, or two to three years depending on your vehicle’s condition? Failure to do so may result in complications that will cause no brake fluid to come out of rear brakes when bleeding.
Some of the complications include; bleeding using a wrong procedure, something wrong with the proportional valve, or a faulty bleed screw. It can also be due to faulty flex hose and calipers. Regardless of the cause, fixing this issue will take you a significant amount of time since it is tedious and a relatively long process to undertake.
In this article, we are going to focus on how to brake bleed and the various methods of bleeding the brakes. We will also dive into the reasons why brakes can’t bleed, and most importantly; why there is no brake fluid to the rear brake when bleeding.
Let us jump into the various reasons why your brakes cannot bleed and how to go about fixing it:
Wrong procedure – Methods of brake bleeding
There are five methods of bleeding the brakes. Some of them you can do solo or with two people. You will also need to spend a significant amount of money on some of these methods, while others are cheap and relatively easier to do.
Brake bleeding aims to get rid of the air bubbles that are compressible in a system that shouldn’t have any compressible gases.
- Pump and hold method – this will require two people. One person steps on the brake pedal while the other individual opens one bleed screw at a time to let the air escape.
- Pressure method – it requires the use of a pressure pump. All you have to do is connect the pump to the master cylinder to pressurize the system while the bleeder valves are opened; one after the other.
- Vacuum method – entails the use of a vacuum pump that connect to the bleeder valve. The vacuum pump is used by opening and closing it to allow the extraction of brake fluid till the air bubbles are completely cleared from the system.
- Reverse method – you can use a pump to push the fluid via the bleeder valve into the master cylinder. Air will rise in the brake fluid naturally to escape out of the brake system.
- Gravity method – this method is the simplest and only requires one person. Since the reservoir is placed higher than the bleed nipple, opening the bleed nipple causes the brake fluid to trickle down out of the nipple.
You can improve these processes using 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.
If you have the correct procedure, then brake bleeding won’t cause you any problems at all. However, if you missed a step in any of the methods mentioned above, the procedure can lead to disastrous outcomes on the road. To fix this, go back to the procedure steps and double-check if you followed the instructions to a T.
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.
To diagnose the proportional valve, you must disconnect it from the system and use a sprayer to pass fluid through. The sprayer should be filled with a clean generic fluid that will be squatted through the four openings of the valve.
If the fluid passes through all the openings, then the issue isn’t the proportional valve. If the fluid fails to pass through one opening, you can conclude that you need a replacement part. Go to your local mechanic shop or search online for the valve that is suitable for your vehicle.
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.
To fix faulty bleed screws, you first have to check for any blockage, leaks, or corrosion in the seat of the screw. If you notice any of these, then it may be time to find replacement parts.
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.
All you need to do to fix this problem is to analyze the hoses carefully. Look at their overall condition and check for any leaks in the internal and external walls of the hose. Proceed to apply pressure on the brake pedal to pump brake fluid through the flex hose. In case there is a bulge in the hose, you can conclude that it is blocked. A replacement flex hose will help fix this.
Something wrong happened to Caliper
The brake caliper faults can be causes of leaking seals, seized pistons, seized pins, and sliding brake caliper pins. The most prevalent of these causes is seized sliding pins. The pins fail when boots in aging cars break down, allowing for moisture absorption that will lead to corrosion and the seizure of the brake pins.
All of these causes will affect the braking issues but not the brake bleeding issue.
For the brake bleeding issues, you will often pinpoint the cause of a caliper that incorrectly fitted. The calipers are sensitive to direction, meaning that calipers 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.
Proceed to change the sides respectively, making sure you do not mix them.
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.
Perform the same procedure you used to check the flex hose for any blocks and leaks. If you press the brake pedal and notice a bulge in the pipes, a block is the main issue. The best procedure for this is the pump and hold method.
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.
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.
Like any mechanical issue, regular maintenance and taking various precautions can prevent bleeding rear brakes. Checking the brake fluid during regular maintenance schedules can save you a lot of money and time.
You should also pay attention to the methods you use to bleed your brakes. It is advisable to seek professional training or help with the braking system lest you damage a vital component. All in all, brake bleeding is straightforward and easy to do after a couple of experiences.
Can I just bleed my rear brakes, or should I Bleed All 4 Brakes?
It depends on whether you have an independent brake line. In modern vehicles with independent brake lines, you can bleed one brake caliper, provided the fluid level isn’t below the level mark in the reservoir. Otherwise, you will need to bleed all four brakes to get the desired results.
Can I change brake fluid without bleeding?
You can change brake fluid without bleeding using a pump. Connect the pump to the master cylinder and suck the fluid out of it. Be careful to ensure that the systems don’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 will 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?
Brakes can only work if we use an incompressible liquid such as the brake fluid in the braking system. The reason why you need an incompressible brake fluid is to provide a reliable link between the brake pedal and caliper. This secure connection will help in transferring the hydraulic pressure efficiently throughout the system.