However, the common causes of spongy brakes include system leaks, contaminated brake fluid, and brake bleeding techniques. On the other hand, a spongy brake pedal that occurs due to brake bleed is frustrating. The good thing is, there is a perfect solution, and you’re in the right place.
The main cause why you experience a soft pedal is due to air trapped inside your hydraulic brake fluid system. Perhaps, recently you have replaced the rotors or disc brakes pads, then you’re likely to lose confidence with your brakes.
This is because the pedal feels soft and infective until rotors and pads are bent in. Don’t get worried. It is normal, and braking lightly can solve that poor pedal feel.
There are different methods to solve the problem. But the preferred option is to open the bleed nipple and push the caliper piston home.
Nevertheless, you now know there are three causes of spongy brakes. You also know what you can do to fix them. So, the most important thing is eliminating brake bleeding procedure errors.
Brake Bleeding Techniques
Most likely, you have never done brake bleeding before. But if you have to do it, you need to check your technique. It isn’t hard to bleed the brakes successfully, but you’re required to nail vital steps.
Remember that this isn’t something you will do every day, therefore worth checking the technique. Again, the procedure isn’t complex, but like most jobs, bleeding the brakes requires essential steps.
Let’s now explore some spongy brake repairs you can do.
How to Repair Spongy Brakes
Bleeding refers to a process where you purge the hydraulic system with trapped pockets of air. In the system, the trapped air can be compressed, leading to a horrible spongy pedal experience. To solve the problem, you need to follow various steps – but they depend on the brake bleed procedure you use.
In the article, we shall look at 3 DIY techniques used – although vacuum brakes are the common technique.
Here are the three techniques worth checking:
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1. Vacuum Method
This method uses the vacuum as an option to pull brake fluid via line, releasing trapped air. It is a simple, convenient process.
- Brake bleeding kit
- Wrenches of different sizes – 8 to 11mm
- Fresh fluid
You are now aware of things you need in this method. Let’s now check the procedure:
- Remove the cap, set it aside and add a fluid reservoir.
- Attach your clear vacuum bleeding hose to your wheel cylinder or brake caliper from the brake line.
- Apply grease at the bleeding nipple threads. It will prevent the air from entering into your system via those threads.
- Now open your bleed nipple to apply vacuum.
- Continue checking and topping up fluid reservoirs.
- The hose will now run free from air, so you need to close the bleed nipple. You should do it under a vacuum.
- Repeat the process to each brake line and finish the brake line near the fluid reservoir.
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2. Pump & Release Method
The other method is the pump and release procedure. But, you can’t do it alone; you need a helping hand. One person will build brake system pressure while the other releases the fluid.
- Fluid bottle
- Clear hose
- Wrench of different sizes – 8 to 11mm
- Fresh fluid
- Remove the cap and top up fluid in the reservoir
- Add fresh fluid to the bottle and submerge it at the bottom of the hose.
- Attach your bleeding hose to the wheel cylinder or caliper bleed nipple.
- Apply grease on these nipple threads to prevent air from entering the system.
- One person will pump the brakes various times and then hold those brakes pedal down.
- The other will open the bleed nipple to release fluid pressure and trapped air.
- Close the bleed nipple, repeat the process various times to ensure fluid runs free of air in the hose.
- During the process, continue to top up the fluid reservoir.
- Repeat the process to all brake lines.
Remember that this method isn’t recommended for old vehicles – particularly those not having regular fluid maintenance. So, you will risk damaging its master cylinder seals because the brake pedal goes to floor when engine running.
Older braking systems develop corrosion on their piston plunger. Thus, leading to damages to the master cylinder seals.
3. Gravity Method
The gravity method is the least preferred option. However, the process is successful, although some systems require a few pumps to move things along.
- Brake bleeding bottle
- Clear hose
- Wrenches between 8 to 11mm
- Fresh fluid
- Remove the cap and top up the fluid reservoir
- Add fresh fluid in the bottle and submerge the hose below the fluid
- Attach the bleeding hose to the wheel cylinder nipple or caliper.
- Apply the grease to the nipple threads to prevent air entrance.
- Open the bleed nipple for fluid to gravity bleed.
- Refill the fluid reservoir regularly.
- Close the bleed nipple after the hose runs without air
- Variation of this process is that you need to pump the brake pedal to ensure fluid moves through the brake lines.
The method will work effectively but is least used because it will take a longer time. Moreover, you have to pump the brakes, which may damage the seals of your master cylinder.
The fluid quality and quantity are essential. But keep in mind that one of the features of hydraulic brake fluid is hygroscopic. And that means it attracts moisture which is a significant problem.
When the fluid becomes old, the moisture content will boil to form steam. So, the steam formed isn’t compressible, which makes the pedal sink to the floor.
What are Symptoms Of Contaminated Fluid?
The problem is experienced after the brakes get warm for a while. But when it is cold, there is no issue at all.
Fixing the Problem:
The solution to this problem is replacing the brake fluid. But, remember, you can’t drain brake fluid as you do
with motor oil. Therefore, to replace old fluid, you should repeat the processes of the brake bleed technique.
With a quarter-liter of brake fluid, it is enough to flush the system.
The recommended method is vacuum brake bleed. That’s because it will make your job easier and mess-free.
Moreover, ensure you replace the brake fluid after every three years. You should also use the recommended fluid type on the reservoir cap.
Avoid mixing glycol-based DOT 3, 4, or 5.1 with silicone-based DOT 5. This is because you can damage your brake system. The difference between these fluids is their boiling point.
A higher DOT means a higher boiling point, which is suitable for use.
Due to pressure in the hydraulic systems, there is a higher chance of getting a leak. And when the fluid leaks, there is a higher chance the air leaks in and loss of brake pressure.
It is evident there is a fluid leak when you find wet, oily patches on the brake components. Remember that even the most minor leak allows the air to enter the lines.
The common areas prone to leak include:
- Caliper Seals – when brake calipers seals are damaged, they cause a fluid leak.
- Bleed Nipples – corrosion occurs on bleed nipples and prevents beveled seat sealing.
- Flexi Hose Unions – when Flexi are corroded.
- Rear-Wheel Cylinder Seals – these are the common failures and fitted to those vehicles having rear drums.
- Brake Unions – when unions are corroded, they result in leaking.
- Brake Lines – corrosion leads to leakage.
Faulty Flexi Brake Hose
If you have a faulty brake hose, it causes a spongy feel. This particularly happens with older cars. The rubber hose may wear and tear. And because the hose has an inner and outer wall, when there is a rupture, it will prevent fluid loss.
Fixing Faulty Flexi Brake Hose
Replace all the brake hoses because even others will be failing later. Then, bleed the system.