When you are replacing or repairing your brakes it is important to bleed the air out of the system. Air is easily compressible compared to liquid brake fluid and if bubbles are trapped in your lines you will end up with a soft brake that won’t perform well. Also the air will get entrapped in the fluid and cause poor breaking once your brakes heat up.
It is also important to change the fluid in your system when it gets black. Brake fluid has an indicator built into the fluid and when it is past its life it will turn black so when bleeding your lines you want to flush all of the dark colored fluid out of the system.
In most car shops bleeding brakes is a 2 man service.
One tech sits in the car and pumps the brake peddle while another is under the car with a bleeder valve wrench opening and closing the valve.
To perform the job you should make sure that you have a container to catch the fluid as it shoots out the bleeder valve. The pressure is pretty much like a squirt gun so be ready to angle the container and wear eye protection.
The Tech under the car should test the valve by cracking it open about a half turn just to make sure it is free. Sometimes these valves can get dirty and if you find fluid won’t flow through the valve you will have to replace it before you can bleed the system.
When you are finished bleeding the brake you are working on remember to replace the rubber dust cap protector on the bleeder valve to make sure no dirt gets into the valve causing you problems the next time you need to work on your brakes.
Bleeding The Brakes
First fill the Master Cylinder with fresh fluid.
Have the tech in the car depress the brake peddle and hold it down.
Open the Valve at the brake you are bleeding and catch the fluid that comes out.
Close the valve once the fluid stops and tell the tech inside the car to lift their foot.
It is important that the Tech in the car never lifts their foot while the bleeder valve is open or air will be sucked back into the brake system.
Working closely together you should exchange the following dialog as the process it completed.
Tech 1 – Valve open … Press Down
Tech 2 – Down
Tech 1 – Valve Closed … release peddle
Tech 2 – Peddle Up
This is an important task so unlike anything else you do on your car take it serious and talk to each other with proper tone as you work. Remember screwing it up could mean no brakes when you are out on the road.
Single Person Brake Bleeding
Although it is 100% easier to perform brake bleeding with a partner there are times when you might need to perform the work yourself. In this case there are a number of tools that will help you get this job done right.
The first tool is a single person bleeder cup.
This is a very easy tool to use simply attach the end of the hose that comes with the cup to your bleeder valve and open the valve. Once the valve is open you can enter the vehicle and depress the brake peddle a few times until you see a solid stream of fresh brake fluid in the line.
The reservoir cup will hold the dirty fluid that you pumped out and because it is designed so that no air will flow back through the line you can perform the work on your own.
Once you have completed bleeding the brake you are working on you simply close the valve and detach the hose then discard the dirty brake fluid and move on to the next brake.
Vacuum Assisted Bleeders
There are two types of vacuum assisted brake bleeders.
The first is a hand held model that can also be used for testing your vacuum system on your engine.
The way it works is you hook the fluid reservoir to the vacuum pump and attach the hose to the brake bleeder valve. Then open the valve and suck the fluid out of the system by pumping the hand control.
They are pretty easy to use and usually cost under $50
The second type of Vacuum System Brake Bleeder is a professional electric model.
The only difference is the electric pump will suck the fluid out for you and you won’t have to use the hand pump. These models are relatively expensive and beyond most home garage owners needs.
Forced Fluid Bleeder
The final type that is a forced fluid bleeder that is connected to the system and pumps not sucks the fluid through the system.
I don’t know how great this method of bleeding is because it can force dirt through your lines and could also introduce air into the fluid as it is being pumped.
However that is just my opinion and devices of this type probably go through heavy testing since they are used for a pretty delicate and important part of car care.
If you are buying a pump system make sure you get it from a well known tool maker.
Custom Solutions
There are a number of other non-conventional methods to bleeding your brakes that use special one of a kind parts and products. One such product is a bleeder valve that has a one way stop valve design.
Although they look pretty much the same from the outside hey use a spring loaded ball bearing that will only let fluid flow in one way but the are prone to clogging and short lifespans.
This type of custom bleeder valve must be installed and ordered for each vehicle needed and for this reason they are not so useful for a general mechanic that will be servicing many different car types.
They are also relatively expensive costing up to $15 per wheel on some models of cars.
They may be an option for a weekend racer that is constantly servicing their equipment but in all reality if you need to perform the work yourself you could purchase a $15 bleeder cup and have the same results not to mention the fluid would be off your floor and in the reservoir cup.
Bleeder Wrenches
Although you can probably perform the work with a standard box or closed end hand wrench there are offset wrenches made specifically for bleeding brakes. They make it easy getting into tight locations and are helpful because they won’t slip off a bleeder valve nut while you are working on it.
They are not a necessity but if you are doing the work a lot then it might be worth the $5 they cost.
Special Note
This HowTo did not cover all of the aspects of brake bleeding. The process is something relatively easy to perform and much easier then actually servicing your brake pads shoe, caliper pistons and wheel cylinders.
However Bleeding Brakes is the final step of most brake servicing and it needs to be performed correctly. To learn this skill you should really be taught in person. Some Tech Schools provide night and weekend classes on general maintenance and a 6 week course might only cost $75 and get you all the hands on education you need to take care of your car.
If you feel you can do the work yourself then get a repair manual specific to your model vehicle and follow their instructions. If you find you are lost in the middle of the process call for a tow to your local service station and have a certified technician finish the work.
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