Bleeding air out of the brakes is often tiring, especially if it doesn’t seem to be working. However, you can check a few things, like a clogged bleed valve, before maybe trying a different method.
If no brake fluid coming out when bleeding, the cause could be a bad master cylinder, a clogged bleed valve or brake lines, cracked hoses, the proportioning valve, or the calipers.
Solutions vary depending on the source, but we’ll provide a step-by-step guide for each cause to make it easier.
Understanding Brake Fluid System
The brake fluid system plays a crucial role in vehicle safety and performance. Proper understanding of its components and functionality enhances maintenance and repair efforts.
Importance of Brake Fluid
Brake fluid transfers force from the brake pedal to the brake components, enabling effective stopping power. It’s hygroscopic, meaning it absorbs moisture over time, which can lead to reduced boiling points and compromised braking performance.
Regularly checking and changing brake fluid ensures optimal functionality and prolongs the life of the brake system.
Brake System Components
The brake system consists of several key components that function together to create hydraulic pressure. Key components include:
- Master Cylinder: Converts the pedal input into hydraulic pressure, pushing brake fluid through the system.
- Brake Lines: Rigid or flexible tubes that transport brake fluid from the master cylinder to the brakes.
- Brake Calipers: Squeeze the brake pads against the rotor to create friction and slow the vehicle.
- Brake Pads: Friction material that presses against the rotor, slowing the wheel’s rotation.
- Brake Rotors: Metal discs that provide a surface for the brake pads to create friction.
- Brake Booster: Enhances the force applied to the master cylinder, requiring less effort from the driver.
Understanding these components and their functions helps identify issues, such as the absence of brake fluid during bleeding.
What Does Brake Bleeding Do?
Brake bleeding removes air bubbles from the brake lines, ensuring that only brake fluid fills the system.
Air in the brake lines can result in a “spongy” or unresponsive brake pedal, which may cause a delayed braking response. The brake bleeding process is also essential if you’ve recently replaced brake components or drained the brake fluid.
Symptoms Of No Brake Fluid Coming Out When Bleeding
- Brake pedal sinks to the floor or feels mushy.
- Brake fluid leaks around the master cylinder area.
- Uneven braking performance or a restricted fluid flow to one or more brakes.
- Visible corrosion or wear on the brake lines.
- Difficulty opening or turning the bleeder valve.
- No fluid flow even when pressure is applied.
- Spongy or ineffective brake pedal.
- No fluid coming out even with pressure applied.
- Hard brake pedal with minimal response.
- Reduced brake pedal pressure.
- Hissing sound (indicating a possible vacuum leak).
- Uneven or lack of fluid flow.
- Pedal remains spongy or inconsistent.
What Causes No Brake Fluid Coming Out When Bleeding?
If no brake fluid is coming out from the bleeding port in the brake caliper, it is an indicator that there is a problem. Ensure that you solve this problem before it results in danger. Here are the reasons why the brake doesn’t bleed:
#1. Faulty or Worn Master Cylinder.
The master cylinder is responsible for moving brake fluid through the brake lines when you press the brake pedal. If the master cylinder is failing, brake fluid may not be effectively pushed through the system, leaving you with no fluid flow at the bleeder valve.
#2. Clogged or Damaged Brake Lines.
Brake lines can become clogged with debris, corrosion, or old brake fluid deposits over time, especially if the fluid hasn’t been changed regularly. A blockage in the brake line can prevent fluid from reaching the bleeder valve.
#3. Blocked Bleeder Valve.
The bleeder valve itself may be clogged with rust, dirt, or brake fluid residue. If this small valve is blocked, it can prevent brake fluid from flowing out.
#4. Air Trapped in the Master Cylinder.
If air is trapped in the master cylinder, it can interfere with the brake fluid flow. This issue often occurs after brake work, such as replacing a master cylinder or when the brake system has been opened.
#5. Faulty Brake Booster (Power Brakes).
In vehicles with power brakes, the brake booster amplifies pedal pressure. A failing booster may disrupt the pressure needed to push brake fluid through the system, leading to no fluid flow during bleeding.
#6. Improper Bleeding Sequence.
Each vehicle has a specific brake bleeding sequence that must be followed to ensure proper fluid flow. Not adhering to this sequence can lead to ineffective bleeding and issues like no fluid coming out at one or more wheels.
Diagnosing the Issue
Before attempting any repairs, it’s crucial to accurately diagnose the cause of the problem. Here are some steps you can take to identify the source of the issue:
#1. Inspect the Brake Lines and Hoses.
Visually inspect all brake lines and hoses for signs of damage, leaks, or corrosion. Look for cracks, bulges, or soft spots that could indicate a problem. Pay particular attention to areas where the lines or hoses are exposed to heat or vibration.
#2. Check the Master Cylinder.
Inspect the master cylinder for leaks or signs of damage. Ensure that the brake fluid level is adequate. If the fluid level is low, it could indicate a leak in the system.
#3. Test the Bleeder Valves.
With the engine off, carefully open each bleeder valve on the front calipers. If fluid flows freely, the valves are not restricted. If there is no flow or a very weak flow, the valves may be clogged or damaged.
#4. Check for ABS Module Issues.
If you suspect a problem with the ABS module, you may need to have it diagnosed by a qualified mechanic. This typically involves using a specialized diagnostic tool to check the module’s operation and identify any faults.
How to Fix No Brake Fluid Coming Out When Bleeding?
Since we are already aware of all the causes of this problem, we need to know exactly how they affect the brake fluid.
In this section, you will know how each reason leads to the lack of brake fluid when bleeding the brakes. Along with that, you’ll also find the solutions for each of them.
#1. Check The Brake Hose For Damage.
The brake hose is the component that carries the brake fluid to the dynamic brake calipers from the reservoir. This brake hose is exposed to the environment outside, which affects them gravely.
This rough environment can cause tears, clogging, and corrosion to the brake hose. As a result, the brake fluid is contaminated and starts leaking.
In such circumstances, the brake fluid lacks pressure and can’t reach the master cylinder or brake calipers. So, no brake fluid will come out when you’re bleeding the brakes.
To fix this, firstly, check the brake hose thoroughly for cracks and tears on the inside and outside walls. If there is only corrosion on the walls, clean it up with baking soda. Apply pressure on the brake pedal and examine if the brake hose is clogged.
If you see no fluid passing through the brake hose and notice a bulging, the brake hose is fully clogged. In that case, replace the brake hose with a new one.
#2. Inspect The Brake Calipers.
A damaged or clogged brake caliper can directly affect the brake bleeding process. The brake fluid must pass through the brake caliper to reach the bleed screw.
If there is a blockage inside the caliper, it fails to run smoothly. So, there is a lack of brake fluid coming out when bleeding.
Firstly, detach the rubber brake hose from the brake caliper to check the inside. Apply pressure to the brake pedals to check if the brake fluid runs inside.
If you find debris or dirt inside the brake caliper, that is the reason for the clogging. Blow compressed air into the brake caliper to clear up the junk inside.
If it doesn’t work in removing the buildup, get the brake caliper for servicing or replace it with a new one.
#3. Find The Blockage In the Bleed Valve.
The bleed valve releases the air and pressure from inside the system. Over time and without maintenance, debris and corrosion can accumulate in the brake valve.
Especially if the bleed valve doesn’t have a rubber cap, it is prone to get clogged sooner. Hence, no air or brake fluid will come out while bleeding.
You will need to unscrew the brake valve first carefully. Let the remaining brake fluid bleed out by pressurizing the brake pedal.
Blow compressed air inside the bleed valve to blow away and remove the debris. Next, spray a good brake cleaner inside the brake valve and use a thin brush or pipe to scrub it.
#4. Figure Out The Bleed Screw Issues.
When the bleed screw is open, the brake fluid is disposed of. This is the final opening of the hydraulic system during the bleeding process.
If the bleed screw refuses to open, there will be no way for the brake fluid to get out while bleeding.
A hardened bleed screw due to rust can prevent the screw from opening and letting the brake fluid out.
Try opening and closing it smoothly to confirm that the bleed screw is facing issues. It is located at the top point of the fluid chamber behind the brake caliper. If it resists or is hard to move, the bleed screw is shut due to water, dust, and mud buildup.
The first fixing measure for this issue should be spraying some lubricant onto the bleed screw and then trying to open it. Use WD40 lubricant on the screw to ease it out of the way.
You can use an air hammer to remove the rust from the bleed screw. A steady vibration will be provided to the bleed screw, which will shake out all of the rust from the component.
Thus an air hammer can remove the problem without damaging the bleed screw even the slightest.
If you’re dealing with a completely broken or damaged bleed screw, it is better to replace the whole brake caliper. You can’t get such a broken screw out of the caliper safely.
#5. Examine The Proportional Valve.
A big sign of the proportional valve issue is the failure to bleed, specifically the rear brakes. If you notice the front brakes bleeding just fine and only face no brake fluid coming out of the rear brakes, the problem is the proportional valve.
The function of the proportioning valve is to distribute the brake fluid pressure evenly. This valve lets the brake fluid flow to the rear axles by opening up when you lightly press the brake.
However, during brake bleeding, a huge amount of pressure is suddenly released from the bleed valve. The proportional valve pinpoints that loss of pressure and closes up completely or partially.
Hence, the brake fluid will not be able to flow to the rear axle while bleeding and resulting in no brake fluid coming out.
In order to get rid of this issue, you will need to reset the proportional valve. Follow these steps to reset this valve:
- As the first step, tighten up the rear brake bleed valves.
- Press down on the brake pedal without removing your feet.
- Take off the front brake bleed valves and keep them in that situation for ten seconds.
- Do this same process several times until the proportional valve clicks to indicate it is reset.
If resetting the valve doesn’t work, detach the valve from the braking system. Use a clean fluid to spray through the passages of the proportional valve.
If you see that the fluid does not pass through a single one of the four passages, you will need to replace the proportional valve.
#6. Check For Brake Line Blockage or Leaks.
The line connecting the brake fluid system to the brake calipers is the brake line. Any blockage in this line can stop the brake fluid from traveling to the destined component.
The wrong kind of brake fluid can cause this. The corrosion and blockage can also lead to cracks or holes in the brake line.
The cracks can leak the brake fluid out of the brake line. As a result, the brake fluid lacks the necessary pressure and amount inside the brake line. When bleeding the brakes, the brake fluid doesn’t come out.
Inspect the brake lines thoroughly to locate the tears and cracks along their length. Then, detach the brake lines to clear up the blockage using a plunger or denatured alcohol.
You can also opt for an air compressor to flush out all the debris and dirt causing the blockage. If cracks or holes are beyond repair, replacing the brake line might be the best option.
#7. Analyze The Master Cylinder For Issues.
The master cylinder is a mandatory component of the braking system. It converts the brake pedal pressure into hydraulic pressure.
A leak in the master cylinder leads to the brake fluid level to reduce. It also decreases the pressure needed for the brake fluid to reach the brake caliper.
A good sign of a faulty master cylinder is that every time you press down the brake pedal, the brake fluid in the reservoir starts bubbling.
Such a faulty master cylinder is a probable reason for no brake fluid coming out when bleeding.
Repairing the master cylinder can be an extremely difficult job. Often, it might lead to contamination of the brake fluid instead of a good fix.
So, replacing the master cylinder is the best idea to fix this issue. Take the help of a professional to complete this replacement.
FAQs.
Q: Can I Change the Brake Fluid Without Bleeding?
When getting rid of old brake fluid, you have to bleed it by opening the bleed screws and adding the new brake fluid at the same time. Leave the bleed screw open until you find the new brake fluid coming out of the bleed screw. You can differentiate it by its fresh color.
Q: Does the Engine Need to Be Running to Bleed Brakes?
No, when bleeding the brakes, the engine has to be shut off to prepare a good quantity of pressure before opening the bleed screw. This will not happen when the engine is running.
Q: Can I Mix Old and New Brake Fluid?
Brake fluid is prone to absorbing water. Therefore it is crucial to change the whole capacity of the brake fluid every two years and put a new brake fluid of the proper type.
Q: Why Are Brakes Still Spongy After Bleeding?
When bleeding, you depress all the pressure in the circuit. After closing the bleed screw, you have to press some more string presses on the brake pedal to get back the brake’s pressure and make sure that there is no pressure leakage in the brake circuit.
Final Words
We are now aware of the importance of brake bleeding and how it affects restoring the brake power of the car. It is vital to check the brake components regularly to ensure that there is no leakage or any torn part that may make brakes fail when driving.
It is recommended to get your brakes checked by an expert to ensure that every part is okay and working properly.