Spongy or sinking brake pedal: causes and what you should do

The brake pedal should feel firm and stay at the same height. If it feels spongy, if you have to press further than you are used to, or if it slowly sinks away, something is wrong in the hydraulic brake system. Below you can read what the causes are, when you should stop, what the Dutch APK (MOT), the periodic vehicle inspection, checks and what we do in our workshop in Rotterdam.

By the team at Autobedrijf Willemsbrug, RDW-approved APK (MOT) test station since 1979 · Updated 8 November 2026

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The short answer

A soft, spongy or sinking brake pedal means that there is air, moisture or a leak in the brake system, or that the master cylinder is leaking internally. Brake fluid absorbs moisture from the air. According to brake manufacturer Textar, the fluid must be replaced at 3.5 percent water, and most manufacturers therefore use an interval of two years. If the pedal sinks while you hold it down, or becomes soft after a long descent, stop and do not drive any further. We find the cause, bleed the system, replace the brake fluid or replace the leaking part. We tell you the cost in advance.

Brake service at Autobedrijf Willemsbrug: brake pads, discs, fluid, calipers, hoses and the handbrake or electric parking brake, for all makes, including hybrid and electric cars, vans and motorhomes up to 3,500 kg. We first measure what is worn, replace only that and show you the old parts. We tell you the price in advance based on your registration number, and we only do extra work with your approval. Call +31 10 479 00 00 or drop by. You bring the car and we call you when it is ready. A loan bike is free while one is available. Saturdays too. Our team speaks English. More about our brake service

What does a soft, spongy or sinking brake pedal mean?

The pedal tells you how the hydraulic system is doing. When you press the pedal, the master cylinder pushes brake fluid through the lines and hoses to the calipers and wheel cylinders. Fluid cannot be compressed, which is why a healthy pedal feels firm. If there is air or vapour in the system, you compress that first before the brakes engage. That feels spongy. If fluid is leaking away, you have to press further to build up the same pressure. This is how to read the pedal:

What you feel What it usually means
Spongy, springs back, brakes only after a lot of travel Air in the system or brake fluid with too much moisture
Pedal sits lower than before, but feels firm there Fluid loss, worn brake pads or drum brakes that are not adjusted properly
Pedal slowly sinks while you hold it down Master cylinder leaking internally, or a leak in a line, hose, caliper or wheel cylinder
Pedal becomes soft after a long descent or repeated hard braking The brake fluid is boiling from the heat (vapour lock), often because the fluid is old
Pedal is hard and the car brakes poorly Brake servo or vacuum hose faulty, not a hydraulic problem
Pedal pulses up and down or vibrates Uneven thickness of the brake disc, see car shakes when braking

Based on the symptom descriptions of the ANWB (master cylinder, brake fluid), the ADAC and Bosch.

If the red brake warning light comes on at the same time, the brake fluid may be too low according to the ANWB, the Dutch motoring organisation. Stop the car and look in the reservoir. Read also brake warning light on: causes and can you drive on.

Can I still drive with a soft or sinking brake pedal?

Preferably not, and in three cases certainly not. A soft pedal is not a complaint to wait and see about, because the cause can get worse in a short time. This is our rule:

Can I still drive? If the pedal sinks while you hold it down, goes almost to the floor, or becomes soft after a long descent or a few hard stops, stop in a safe place, do not drive any further and call +31 10 479 00 00. Have the car brought to our garage. If the pedal has felt slightly spongier than before for some time, but stays put and the car brakes normally, drive carefully to the garage. Keep extra distance from the car in front and have it checked soon.

Pumping the pedal can build up pressure temporarily in an emergency, but it does not solve anything. Bosch writes about vapour lock, the boiling of the brake fluid, that it can lead to a total loss of the brakes.

What are the causes of a soft or sinking brake pedal?

There are five causes we come across most often in the workshop. They all have to do with the brake fluid or with the pressure in the system.

  1. Air in the system. Air gets in when the system has been opened, for example after replacing a caliper or hose, or when the reservoir has run empty. Air can be compressed, fluid cannot. The pedal feels spongy. Solution: bleeding.
  2. Old brake fluid with moisture. Brake fluid of the DOT 3 and DOT 4 types is hygroscopic: it attracts moisture from the air, the ANWB writes. That lowers the boiling point. During hard or prolonged braking, the water in the fluid can boil and vapour bubbles form. The pedal can then become soft or sink. Solution: replacing the fluid.
  3. A leak. A rusted brake line, a cracked brake hose, a leaking caliper or wheel cylinder. The fluid level in the reservoir drops, the pedal goes deeper and sometimes you see a wet patch near a wheel or under the car. Solution: replacing the leaking part and bleeding. More in brake hoses and lines: rust, leaks and the APK.
  4. The master cylinder. The seals in the master cylinder wear. The fluid then leaks back internally past the piston, without you seeing anything on the outside. The ANWB names as symptoms a soft or spongy pedal, a pedal that has to be pressed further, less braking power and a pedal that slowly sinks. Solution: replacing the master cylinder.
  5. The brake servo. This boosts the force of your foot with vacuum from the engine or a pump. If it does not work, the pedal feels hard instead and the car brakes poorly. That is a different symptom from a soft pedal, but the two are often confused.

On a car with drum brakes at the rear, a deep pedal can also be caused by drum brakes that are not adjusted properly. And heavily worn brake pads give more travel, because the piston has to move further out.

Why does old brake fluid play such a big part?

Because moisture lowers the boiling point and brakes generate heat. According to Textar, new DOT 4 brake fluid has a boiling point of at least 260 °C. As soon as there is moisture in it, that boiling point drops. Textar gives a wet boiling point of at least 160 °C for DOT 4 and advises replacing the fluid at a water content of 3.5 percent. That moisture gets in slowly through the hoses and the reservoir, even if you drive little.

Source Recommended interval Notes
ANWB Usually every two years According to the maintenance schedule of the car. DOT 3 and DOT 4 are hygroscopic, the boiling point drops and vapour bubbles can form
Textar Every two years Replace at 3.5 percent water. DOT 4 dry at least 260 °C, wet at least 160 °C
Bosch Every two years Car manufacturers recommend bleeding the brake system every two years. Vapour lock can lead to a total loss of the brakes
ADAC At the latest every two years Regardless of mileage. A pedal that can be pressed down very easily without much resistance is a warning sign

Sources: ANWB brake fluid, Textar brake fluid, Bosch white paper on brake fluid (2022), ADAC Bremsflüssigkeit (20 May 2025). Consulted on 6 November 2026.

This is not checked at the APK. According to article 5.2.32 of the Regeling voertuigen, the Dutch vehicle regulations, the inspector only checks that the level in the reservoir is not below the minimum mark and that the cap is on. Old brake fluid is therefore not a rejection point, but it does give you a soft pedal at the moment you need the brakes most. How the fluid is replaced and what the ANWB gives as a cost indication is in brake fluid change: how often and why.

What do we do about a soft or sinking brake pedal?

We first find the cause and then repair only what is needed. A soft pedal has several possible causes, so we do not start by replacing the fluid in the hope that it helps. This is how it goes:

  1. Pedal test: we press the pedal firmly and hold it, as the inspector does at the APK. If the pedal sinks, there is a leak, internal or external.
  2. Level and leaks: we look in the reservoir and check the lines, hoses, calipers and wheel cylinders for moisture and rust, with the wheels turned fully to the left and to the right.
  3. Brake servo: we test whether the pedal sinks further when the engine is started with the pedal pressed. If it stays put, the servo is not working.
  4. Master cylinder: if the pedal sinks without anything leaking on the outside, the master cylinder is the suspect.
  5. Repair: we bleed the system, replace the brake fluid or replace the leaking part. We check the brake fluid and replace it according to the manufacturer’s schedule, usually every two years.
  6. Testing: after the work we test on the brake tester and take a short test drive.

We tell you one price for your registration number in advance and we only repair after you have agreed. As an indication: the ANWB gives € 50 to € 75 for replacing the brake fluid and about € 400 to € 700 for a complete replacement of the master cylinder (ANWB, pages without a date, consulted November 2026). What it costs for your car, we tell you in advance. Everything about how we work is on brake replacement in Rotterdam.

How do you prevent a soft brake pedal?

By having the brake fluid replaced on time and spotting a leak early. This is what you can do yourself:

  • Keep to the interval in the maintenance schedule of your car, usually every two years. Even if you drive little, because moisture gets in with time, not with the kilometres.
  • Look in the reservoir now and then. A level that drops without the brake pads having been replaced points to a leak. Do not top up without thinking and do not mix types: the ANWB writes that DOT 5 may not be mixed with DOT 3, DOT 4 or DOT 5.1.
  • Brake on the engine in the mountains. Change down and brake briefly and firmly instead of long and lightly, so the brakes can cool and the fluid does not boil.
  • Act on the first sign. A pedal that sits slightly lower than a month ago is the moment to have it looked at.

We check the brakes at every service and APK. Not sure? Call us and we will schedule a short brake check. If nothing needs doing, we tell you that too.

Frequently asked questions

Why does my brake pedal sink when I am stationary?

If the pedal slowly sinks to the floor while you hold it down at a standstill, fluid is leaking away. If you see nothing on the outside, the master cylinder is leaking internally past the piston. The ANWB names a slowly sinking pedal as a symptom of a faulty master cylinder. Do not drive any further and have the car brought in.

Can I top up the brake fluid myself if the pedal is soft?

No, preferably not. A low level has a cause: worn brake pads or a leak. Topping up hides the leak and does not remove the air in the system. If you do top up, use the same type that is in the reservoir. According to the ANWB, DOT 5 may not be mixed with DOT 3, DOT 4 or DOT 5.1. Have the system checked afterwards.

Is a soft brake pedal normal after replacing the brake pads?

No. After replacing brake pads, the pedal should be firm again after pumping a few times, because the pistons are then up against the new pads. If the pedal stays spongy, air has got into the system or a part has not been fitted properly. Have the garage that did the work bleed and check the system.

Why does the brake pedal become soft on a long descent?

Because the brake fluid is boiling. During prolonged braking, the discs and calipers get hot and that heat passes to the fluid. Old fluid with moisture boils at about 160 °C (Textar, wet boiling point DOT 4), new fluid only at 260 °C. The vapour bubbles can be compressed and the pedal sinks. Stop, let the brakes cool down and have the brake fluid replaced. Brake on the engine when going downhill.

Does a car with a soft brake pedal fail the APK?

Yes, if the pedal sinks during the pressure test or is limited by a stop. If in doubt, the inspector presses the pedal with no more than 700 N and holds it for about 10 seconds (article 5.2.31). A leaking part is also a rejection point. Only a slightly spongy pedal without a leak is not covered by the requirements. Read more in failed the APK on the brakes.

How long can I drive with a soft brake pedal?

There is no safe answer to that. If the pedal sinks or goes almost to the floor, you do not drive. If the pedal has been slightly spongy for a while but stays put, drive only to the garage and keep extra distance. A leak does not get smaller and moisture in the brake fluid does not disappear by itself.

What is the difference between a soft pedal and a hard pedal?

A soft or spongy pedal points to air, moisture or a leak in the hydraulic system. A hard pedal where you have to push hard and the car still brakes poorly points to the brake servo or the vacuum hose. If the engine is not running, a hard pedal is normal: the servo then gets no vacuum.

Brake pedal soft or sinking? Call us

Call +31 10 479 00 00 with your registration number. We find the cause, repair only what is needed and we tell you the cost in advance.

You will find us at Boterdiep 11 in Rotterdam-IJsselmonde, close to Stadion Feijenoord (De Kuip). We work by appointment. For a quick question or check you can walk in without an appointment.

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