This page is dedicated to helping you find out why your brakes won’t bleed. On this page, you’ll find a short video outlining the top causes of vehicle brakes that refuse to bleed. I share some mechanics’ top brake bleed tips together with links to tools that help make the diagnosis and repair a ton easier.
Brake fluid, as you know, should be changed every four years, and that’s because old fluid contains contaminants, including water, that results in a poor pedal feel after bleeding. Not only that, old fluid can cause internal system corrosion, and that can mean a complete brake system overhaul.
Mechanics Brake Bleed Tip
There are a few common reasons for a brake system that won’t bleed, and the video above covers them. Top of the list is the brake bleed procedure itself.
Bleeding brakes isn’t difficult, but if it’s not done correctly, the results can be frustrating. I’ve included a tool below that makes bleeding a lot easier. It’s a one-person bleed kit and removes the need to pump the brake pedal altogether.
Here are a few brake bleed tips:
- Inspect brakes system, check for corrosion, leaks, check for fluid contamination, etc
- Begin the bleed process with the wheel farthest from the reservoir and work towards the closest
- Clean all bleed valves and apply grease around threads before opening (prevents air from entering the system)
- Bleed each wheel three to four times each
- Top up the fluid reservoir after bleeding each wheel
- If the system runs dry, the ABS brake modulator might need to be activated, which will require a scan tool
If the system still doesn’t bleed, then try the gravity bleed – open bleed screw one wheel at a time (farthest wheel from reservoir first) and allow it to drain into a container. It may take some time for the fluid to start flowing. Keep the reservoir topped up throughout the process.
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
Poor Brakes After Brake Overhaul
If the brakes felt fine before an overhaul but now won’t bleed or do bleed but feel like crap, then check the following.
Fitted new pads – Maybe you fitted new pads or pads and rotors, and you feel the brake pedal is soft and has a ton of travel. That’s normal behavior, but you are correct in questioning it. Until the new pads and rotor surface mate or bed in the brakes will feel horrible. After about 8 – 10 normal brake applications, the brakes will feel fine.
Fitted new rear brake shoes – Brake shoes are a bitch of a job, and after fitting, they need to be adjusted so that they make contact with the drum as soon as the brake pedal is applied. If the shoes are too far from the drum, it creates excessive brake pedal travel.
Fitted new calipers – Fitting shiny new calipers is exciting, but the results are frustrating you. I hear you. Okay, as calipers will fit either side of the vehicle, be sure your calipers are fitted to the correct side.
Your calipers will be marked L and R, but if you can’t find the marking, just fit the caliper on the side that allows the bleed screw to live towards the top. That way, the air in the system gathers at the bleed screw and makes for successful bleeding.
Hey, don’t worry about it. If we didn’t make mistakes, we wouldn’t make anything.
New ABS brake modulator – If you fitted a new modulator, you’d likely need to activate the modulator solenoids to fill with fluid and remove air pockets. To do that, you’ll need a scan tool with that functionality. I’ve included one below, but fair warning, it’s a little spendy.
Brake Repair Tools You May Need
Here are a few brake repair tools to help you nail the brake bleed procedure like a pro!
Brake fluid moisture tester, this simple tester is a really fast way to check the moisture content of your fluid. Brake fluid should be changed every three years. Moisture inside the hydraulic system is, as you know, bad for a couple of reasons.
First, it reduces brake performance when the fluid gets hot, and second, moisture inside the system attacks metal components, causing corrosion. This will lead to caliper, brake line, master cylinder, and possible brake controller damage. Picture links to Amazon.com.
Useful one-man vacuum brake and clutch bleeding kit that won’t hurt the pocket. It’s perfect for occasional brake maintenance chores is easy to use, and gets the job done. Picture links to Amazon.com.
Compact brake line flaring tool, the best thing about this tool is its size. This little guy is ideal for flaring brake lines while on the vehicle, but the handle is detachable for bench work too. Flares 3/16 SAE double flare steel and copper. Picture links to Amazon.com.
The Autel MaxiCOM is a shop-level tool. It is capable of reading, clearing fault codes, coding a new battery, placing the EPB module in service mode, and calibration after the repair. It is also capable of activating ABS modulator solenoids when performing a full brake bleed procedure. Picture links to Amazon.com.
Preston is a leading supplier of quality automotive fluids. This is DOT 3 so remember to check your reservoir cap before ordering. This product is sold by Amazon and is conveniently delivered to your door. Picture links out to Amazon.
3M makes top-quality products. Brake cleaner is likely one of the most used products in a pro shop. It is used not just to clean brake components and prevent brake squeal but also to clean spilled liquids like brake fluid, and oil grease. The cleaner is an aerosol and is powerful enough flush grit from components. Picture links to Amazon.com.
A head-mounted lamp is like having a third hand, a real advantage when you are doing battle. This rechargeable LEd head-mounted lamp is conveniently sold and delivered by Amazon.com.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.