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Spongy Brakes After Bleeding (100% Fix)

A spongy brake pedal after a brake bleed is frustrating, but you’re in the right place, and we’ll get to the bottom of it in this post.

The most common cause of spongy brakes after bleeding is contaminated brake fluid. Usual contaminants include air or moisture in the system. The most common causes include:

  1. Brake bleeding technique
  2. Contaminated brake fluid
  3. System leak

You are correct to bleed the brakes; the most likely cause of the soft pedal is trapped air inside the hydraulic brake fluid system. If you’ve previously done some work, like replaced brake pads or rotors, it’s common to lose confidence in the brakes.

Spongy Brakes 3 Reasons

The pedal will feel soft and ineffective until the pads and rotors bed in (surfaces mate). This is normal, and test-driving and braking lightly will solve the poor pedal feel. Opening the bleed nipple to push home the caliper piston is a preferred method for some when fitting pads; in so doing, it is possible to allow air into the system.

If you used this technique or you’ve replaced brake lines or hoses then you likely have air in the system. Bleeding the brakes using the vacuum method below will fix the problem.

In this post, you’ll learn about the three most common causes of spongy brakes and what you can do to fix them. I understand you have bled the brakes, and they are still soft, so it makes good sense to eliminate a brake bleeding procedure error first.

1 Brake Bleeding Techniques

BRAKE BLEEDING SEQUENCE

Bleeding the brakes isn’t a job you do every day, or maybe you’ve never done it before, so it’s worth checking your technique. Bleeding the brakes successfully isn’t a complex procedure but, like lots of jobs, requires nailing some crucial steps.

Bleeding is, as you know, a process whereby we purge the hydraulic system of trapped pockets of air. Trapped air is compressible, which causes the horrible spongy pedal feel. The process requires different steps depending on the brake bleed method employed.

I prefer the vacuum brake bleed kit, but we’ll cover the three most common DIY techniques used.

If you’ve replaced the brake calipers recently and the brakes won’t bleed, you may find this post useful “Brakes won’t bleed.”

And you may find this video helpful “Brakes won’t bleed.”

Vacuum Method

The vacuum method, as its name suggests, uses a vacuum to pull brake fluid through the lines releasing trapped air. The process is simple, convenient, and a one-man job.

Check out the Brake repair tools page; I’ve listed a simple hand-help vacuum bleeder that works great.

Tools you’ll need:

  • Fresh fluid
  • Wrenches 8, 10, or 11mm usually
  • Brake bleeding kit

The process looks like this:

  • Remove, set cap aside, and top up the fluid reservoir.
  • Starting at the brake line farthest from the brake reservoir, attach the clear vacuum bleeding hose to the brake caliper or wheel cylinder bleed nipple.
  • Apply grease to the bleed nipple threads – helps prevent air enters the system through the threads.
  • Open the bleed nipple and apply a vacuum to the system.
  • Check and top up fluid reservoir regularly.
  • When the hose runs free from air, close the bleed nipple while under vacuum.
  • Move to each brake line and repeat, finishing with the brake line closest to the fluid reservoir.

Gravity Method

This is my least preferred method, it’s usually successful, but some systems may require a few pumps of the brake pedal to move things along. This method is a little different from the vacuum method.

Tools you’ll need:

  • Fresh fluid
  • Wrenches 8, 10, or 11mm usually
  • Brake bleeding bottle and clear hose

The process looks like this:

  • Remove, set cap aside, and top up the fluid reservoir.
  • Quarter fill the bottle with fresh fluid, and submerge the bottom of the hose below the fluid (important)
  • Starting at the brake line farthest from the brake reservoir, attach the clear bleeding hose to the brake caliper or wheel cylinder bleed nipple.
  • Apply grease to the bleed nipple threads – helps prevent air enters the system through the threads.
  • Open the bleed nipple and allow the fluid to gravity bleed.
  • Check and top up fluid reservoir regularly.
  • When the hose runs free from air, close the bleed nipple.
  • A variation on this method includes pumping the brake pedal to move the fluid through the brake lines.
  • Move to each brake line and repeat, finishing with the brake line closest to the fluid reservoir.

This is my least preferred method as the true gravity bleed technique takes longer, and pumping the brakes risks damaging the seals of the master cylinder (higher risk on older cars).

Pump & Release Method

This is how my father taught me to bleed brakes; as a kid, I was the brakeman, and my job was to pump and hold the brake pedal when instructed. This is a two-person procedure, one person builds brake system pressure (brake person), and the second person releases the fluid (release person).

Brake bleeding procedure

To execute this procedure, you’ll need:

  • 2 People
  • Fresh fluid
  • Wrench’s 8, 10, or 11mm usually
  • Fluid bottle and clear hose

The process looks like this:

  • Remove, set the cap aside, and top up the fluid reservoir.
  • Quarter fill the bottle with fresh fluid, and submerge the bottom of the hose below the fluid (important)
  • Starting at the brake line farthest from the brake reservoir, attach the clear bleeding hose to the brake caliper or wheel cylinder bleed nipple.
  • Apply grease to the bleed nipple threads – helps prevent air enters the system through the threads.
  • Brake man is instructed to pump the brakes several times and to then hold the brake pedal down. (important)
  • The release man then opens the bleed nipple and releases the fluid pressure together with the trapped air.
  • Release man then closes the bleed nipple and repeats the process until the fluid runs without air in the hose.
  • Check and top up the fluid reservoir regularly during the process.
  • Move to each brake line and repeat, finishing with the brake line closest to the fluid reservoir.

This technique isn’t advised for older vehicles, especially those without regular fluid maintenance. This type of process requires the brake pedal to go to the floor several times. This runs a real risk of damaging the master cylinder seals.

Older brake systems may develop corrosion on the piston plunger, and running a corroded plunger past its normal travel distance can damage master cylinder seals.

2 Contaminated Fluid

Brake fluid

Brake fluid quantity is important but so too is the quality. Hydraulic brake fluid is hygroscopic (attracts moisture), and that’s a problem. When a car breaks, it turns that kinetic energy into heat energy at the brake rotors.

The brake caliper positioned over the rotor naturally causes the brake fluid inside the brake caliper to heat. This isn’t a problem when the fluid is fresh. However, when the fluid is old, the moisture content boils and becomes steam. Steam isn’t compressible, so the pedal sinks to the floor.

Symptoms:

This is generally only a problem when the brakes have been warmed up for a while and usually isn’t an issue when cold.

The fix:

Replace the brake fluid. Brake fluid isn’t drained like you drain motor oil. Instead, the old fluid is replaced by repeating the brake bleed technique. Approx. one quart (liter) of brake fluid is enough to flush the system completely.

I recommend buying a vacuum brake bleed kit; it makes the job simple and mess-free. Your brake fluid should be changed every three years, and the fluid marked on the reservoir cap is the recommended type.

Mixing DOT 5 (Silicone-based) with DOT 3, 4, or 5.1 (Glycol-based) is a NO No; it will damage your brake system. It is possible to mix the different spec Glycol fluids, but it’s better to keep them separate. The main difference between the different spec Glycol fluids is the boiling point.

The higher the DOT, the higher the boiling point and a higher boiling point is better.

3 System Leak

Your hydraulic system works under pressure; a leak is very possible. If fluid can leak out, then conversely, air can leak in. A fluid leak is usually self-evident. A wet, oily patch around the brake components or lines needs to be investigated. Even the smallest leak will allow air to enter the lines.

Common leak-prone areas include:

  • Bleed nipples – Corrosion on the bleed nipple beveled seat prevents sealing.
  • Caliper seals – Brake caliper seals damage causing fluid leak
  • Rear wheel cylinder seals – Rear wheel cylinder seals are a common failure (only fitted to vehicles with rear drums)
  • Flexi hose unions – Corrosion on flexi to hard-line unions
  • Brake lines – Corrosion
  • Brake unions – Build up of corrosion at unions common

The fix: Find and repair the source of the leak and bleed the system.

Faulty Flexi Brake Hose

Brake flexi hose

A faulty brake hose can also cause a spongy feel, it’s a lot less likely, but I have replaced plenty, especially on older cars. The flexible rubber brake hose fitted between the chassis and the suspension is flexible to allow for relative movement. The constant movement does take its toll and often without any visual cues.

The rubber hose may show signs of wear and tear and age or may not. The hose is constructed with an inner and outer wall; a rupture of either prevents fluid loss.

However, the weakened wall allows the hose to swell and expand instead of sending fluid pressure to the brake caliper, much like squeezing a balloon in the middle. The swelling of the hose causes a horrible spongy soft pedal.

The Fix:

Replace all brake hoses as the others will also be close to failing, then go ahead and bleed the system.

Check out the Brake repair tools I use here on the “Brak repair tools page.”

BRAKE FLUID CHART

Brakes are serious business; if you aren’t confident they are right, go to your local mechanic and have them checked. Alternatively, check out the JustAnswer link below, where you can talk to a mechanic directly right now.

Connect one-on-one with an Auto Mechanic

Related Question

What do spongy brakes feel like? Spongy brakes feel soft and ineffective. Brake pedal travel towards the floor is excessive, and the pedal will only affect the end of its travel.