No Brake Fluid Coming Out When Bleeding Brakes
Chris is Head of Content for FindTheBestCarPrice and is based out of Philadelphia, PA. As a seasoned automotive industry analyst and car enthusiast, he ensures the highest level of quality across all our content and curates our picks for the best deals each month.
Chris studied information systems and marketing at Drexel University and writes about a wide range of topics ranging from car buying tips to troubleshooting common mechanical issues.
When he’s not thinking about cars, he likes to stay in with his dog and make an “attempt” to finish a crossword puzzle (he’s not quite at the Saturday/Sunday level…yet). As a former cheesemonger, Chris still has a “sharp” passion for all things cheese, and his fridge is always loaded with it!
A prevalent issue of brake systems is a low brake pedal level. Numerous automobile drivers have reported that the braking performance deteriorates over time and is not commensurate with the initial purchase.
In such cases, the foremost measure is to perform a brake oil bleeding. This process involves expelling all the brake fluid to eliminate air bubbles and augment the vehicle's braking capacity.
If you attempt to execute a brake fluid bleeding, but it yields no trace of fluid, it becomes a matter of concern. Purging air from the brake system is frequently arduous, mainly if it seems ineffective.
There are several aspects of the problem: "No brake fluid coming out when bleeding.” Let’s look at the causes, how to fix it, how to diagnose it, and more.
Table of Contents
Top 6 Reasons No Brake Fluid Comes Out When Bleeding Brakes
The primary cause behind the absence of brake fluid during a brake bleeding process could stem from obstructions within the brake fluid lines, complications with the bleed screw, clogged calipers, or, in some instances, erroneous protocol implementation.
1. When There's a Blockage in the Fluid Lines
A congested brake fluid line is often responsible for the absence of fluid during the bleeding process.
The brake fluid line, which serves as a conduit or tubing linking the brake fluid system to the brake calipers, is responsible for releasing the fluid to the calipers when the brake pedal is engaged.
Once the line encounters an obstruction, the brake fluid can no longer travel to the calipers.
One of the primary reasons for such obstructions is the presence of contaminants, mainly dirt, in the fluid lines.
Should you notice a blockage in the brake line, it is recommended to disconnect the line on both ends and rinse it with denatured alcohol.
Additionally, an air compressor may expel any debris obstructing the line. After ensuring the line is thoroughly unobstructed, reconnect it to its original position.
2. If the Proportional Valve Is Obstructing the Fluid
The proportional valve harnesses the hydraulic pressure in the braking system to regulate fluid flow. The valve opens up when operating under light braking, enabling the fluid to circulate to the front and rear brakes.
However, when you brake abruptly or with substantial force, the proportioning valve contracts, and the fluid flow to the rear brakes diminishes. Nonetheless, the valve will not close entirely but only partially.
If the fluid is not bleeding from your rear wheel, it could be due to a defective or deteriorating proportioning valve.
A faulty proportioning valve will constrict, impeding fluid flow to the rear wheel. In such cases, it is advisable to replace the proportioning valve.
Although it is not a complicated procedure, having a professional mechanic undertake it might be prudent.
3. Defective Master Cylinder
The master cylinder constitutes a crucial element in the braking process as it facilitates the conversion of the force exerted by the brake pedal into hydraulic pressure.
This is achieved by enabling the brake fluid to circulate to the brake circuit, which is regulated mechanically. Despite its significance, the master cylinder, like other vehicle components, is susceptible to malfunctioning.
If the master cylinder is defective, it can result in brake fluid leakage and a subsequent decrease in fluid levels within the cylinder.
The leakage can also impede the creation of the requisite pressure, causing the fluid to fail to reach the brake caliper during bleeding.
To rectify any issues with the master cylinder, it is imperative to replace the component. Merely fixing the master cylinder may prove futile and might even contaminate the brake fluid.
4. Following the Wrong Procedure
Following an incorrect bleeding procedure can be a substantial factor in the absence of brake fluid during the bleeding process. However, executing the proper bleeding technique is relatively uncomplicated.
It is advisable to have an additional individual, such as a companion, to aid in the Procedure before commencing.
One person could operate the brake pedal while the other carried out the brake bleeding.
5. Damaged Bleed Screws
A bleed screw is a transient portal in the hydraulic brake system that can be sealed with the screw once the bleeding process is complete. It is situated at the highest point behind the brake caliper and is susceptible to several factors.
Factors such as corrosion and dust can make unscrewing the bleed screw difficult. Additionally, even when the screw has been removed, accumulated rust may obstruct the nozzle.
To ease the unscrewing process, one can apply a lubricant like WD40 to the screw and let it sit for some time before attempting to unscrew it. This approach minimizes the possibility of breaking the screw during removal.
If the screw is completely stuck, an air hammer can be employed to remove it. The air hammer's consistent vibrations help to loosen and break up any corrosion in the screw without causing harm to the screw itself.
A broken bleed screw presents a severe challenge, and replacing the caliper may be the only solution. Any further attempts to remove the broken screw may result in additional damage to the caliper.
6. Blocked Brake Caliper
A potential reason for lack of fluid while bleeding one of the wheels could be a blocked brake caliper, wherein a faulty sliding pin is a significant factor.
The sliding pin is housed within the caliper and plays a crucial role in actuating the brake pads against the rotor during braking.
When the caliper's function is hindered due to a clogged sliding pin, immediate replacement is essential.
The malfunction hampers the brake bleeding process and can compromise the brake's standard operation, posing a significant safety risk while driving.
Diagnosing and Fixing the No Brake Fluid Coming Out When Bleeding
The following are effective ways to diagnose and possibly fix the no-brake fluid coming out when bleeding:
1. Inspect the Brake Hose for Possible Damage
The brake hose is a conduit for brake fluid from the reservoir to the dynamic brake calipers.
Unfortunately, this crucial component is exposed to the external environment and thus vulnerable to its harsh effects. As a result, the brake hose may suffer from tears, clogging, and corrosion.
These issues can contaminate the brake fluid and cause it to leak, resulting in insufficient pressure and an inability to reach the master cylinder or brake calipers. Thus, bleeding the brakes may not result in any brake fluid discharge.
To address this problem, it is essential to carefully examine the brake hose for any cracks or tears on both the inside and outside walls.
However, if corrosion is present, cleaning with baking soda is recommended. Additionally, applying pressure to the brake pedal can help detect clogging in the brake hose.
If no fluid passes through the hose and bulging is observed, the brake hose is fully clogged and needs replacement with a new one.
2. Locate the Blockage in the Bleed Valve
The bleed valve is crucial in releasing trapped air and pressure from the braking system.
However, if left unchecked, the bleed valve can become susceptible to debris and corrosion accumulation, notably if lacking a protective rubber cap. This leads to the brake valve getting obstructed, rendering the bleeding process fruitless.
To tackle this issue, the brake valve must be cautiously unscrewed first, and the remaining brake fluid must be allowed to drain by applying pressure to the brake pedal.
Compressed air must then be directed into the bleed valve to eliminate debris, followed by a thorough cleaning with a reliable brake cleaner and a slim brush or tube for scrubbing.
3. Inspect the Proportional Valve
A significant indication of an issue with the proportional valve is the inability to bleed the rear brakes while the front brakes function perfectly.
The proportional valve is responsible for the uniform distribution of brake fluid pressure. It enables the flow of brake fluid to the rear axles by opening up with light brake pressure.
However, when there is a sudden pressure release from the bleed valve during brake bleeding, the proportional valve detects the pressure loss and closes up either partially or entirely.
Consequently, brake fluid will not flow to the rear axle during bleeding, resulting in no brake fluid coming out.
To resolve this issue, the proportional valve must be reset. Begin by tightening the rear brake bleed valves and pressing down on the pedal without releasing your foot.
Remove the front brake bleed valves and maintain this position for ten seconds. Repeat this process multiple times until the proportional valve clicks, indicating that it is reset.
If resetting the valve fails to resolve the issue, detach the valve from the braking system and clean the passages using a clean fluid. The proportional valve must be replaced if the fluid does not pass through any of the four passages.
4. Carry Out a Thorough Inspection of the Master Cylinder
The master cylinder is a pivotal component in the braking mechanism, translating the force exerted on the brake pedal into hydraulic pressure, which is then dispatched to the brake calipers.
Hence, a breach in the integrity of the master cylinder culminates in a diminution of the brake fluid volume, thereby causing a reduction in the hydraulic pressure required to convey the fluid to the brake caliper.
A notable symptom of a malfunctioning master cylinder is the bubbling brake fluid in the reservoir upon every depression of the brake pedal.
Also, a faulty master cylinder could be a likely culprit for the lack of brake fluid when bleeding the brakes.
Fixing the master cylinder is challenging, as it could contaminate the brake fluid, causing more harm than good.
Therefore, replacing the master cylinder entirely is the optimal solution to remedy this problem. Seek assistance from a professional to ensure a successful replacement.
