Matched Content

Monday, July 16, 2012

Front Brake Bleeding By One Mechanic Only

Procedure with photos and video described here is the work of my innovation and it is easy to apply and designed to be done by only 1 (one) mechanic. Tools needed are combination spanner, hose, and container for used brake fluid. At first glance this brake bleeding procedure is similar to the one that already exist. But by lifting the hose higher than nipple and using grease to prevent air enter the system, this procedure can be done by one person only. No need assistance (helper) to open and close nipple many times. With this procedure, brake air bleeding for one wheel can be done in just 15 minutes if no problems. Jack and remove the wheel can take longer time. On some high ground clearance vehicles such as jeep, this procedure can be performed without removing the wheel. Likewise, if you have car lift, brake air bleeding can be done without removing wheels. Because of easy, one with no experience can do it. You can do it in your garage at home.

See a video about three colorful origami boats are sailing together without: fuel, engine, battery, electric motor, and without wind blow. Boats are powered by chemical reaction to provide hydraulic energy.

Photo below shows a hose filled with new red brake fluid after brake bleeding. Used brake fluid is collected in a plastic bottle of mineral water.

In this article, brake bleeding is done for the front brake. To bleed air from the rear brake can be read in the article: Brake Bleeding Practical Procedure By Only One Mechanic.

There is also a simple procedure that uses a pump to push brake fluid in reservoir to go out from nipple. Also there is a procedure that uses a vacuum pump to suck brake fluid from nipple. Although easy, but both procedures require expensive equipment.

Video at the bottom of this post shows the clear brake fluid with air bubbles and red colored brake fluid that come out from brake nipple and go into the transparent hose. A new red brake fluid will replace the old clear brake fluid.

If you just done any repair on piston or cylinder on the wheel or the brake master cylinder (brake pedal cylinder), for example: replacement of rubber seals, it is necessary to bleed air from brake hydraulic system. Air trapped in the hydraulic system will cause no brake pressure. Brake pedal feel light and can be pressed to bottom, and feels like stepping on a balloon or rubber foam. This occurs because the physical properties of air that can be compressed (compressible) and shrink the volume. While the brake fluid can not be compressed (incompressible) or volume always constant even when under pressure.

The usual procedure is requiring two people. One person in charge of pumping the brake pedal until pressure build up, then hold the pedal in a depressed position. Another person is at the wheel to loosen nipple so the air can go out of the hydraulic brake system, and then immediately close nipple again. Brake pedal is then released and pumped again, and so on until the pressure is building up and normal, and pedal does not feel like stepping on a balloon anymore. This usual procedure is written on many websites.

In the video at the end of this article, the bleeding is performed to replace the old brake fluid with new brake fluid. Usually brake fluid is drained every 2 years, please refer to your vehicle service manual. Replacement of brake fluid needs to be done because of moisture or water entering the hydraulic system, and some other material such as: dirt, rubber seal debris, rust, air.

This procedure can also be used to bleed air after a major overhaul on the brake hydraulic system, such as replacement rubber seals in wheel cylinder or in the master cylinder. And can be applied to almost any vehicle using the hydraulic system for brake, including motorcycles.

Brake bleeding should be started from the wheel farthest from the master cylinder. In order for the air and the old brake fluid can get out in the large volume quickly. For cars with the driver position on the right such as Indonesia, Britain, Australia, Japan, Singapore, Malaysia, Hongkong, India, New Zealand, etc. the farthest wheel is the left rear wheel. On some cars, the position of the brake master cylinder is not right near the foot of the driver, on the right side for Indonesia. There are some European cars have master cylinder positioned on the passenger side. Maybe because those cars were originally designed with the driver's position on the left, but later modified to have the driver's position on the right to expand market share.

The first thing that needs to be done before bleeding the brake: open the brake fluid reservoir cap, check brake fluid level, top up to maximum is necessary. The photo below shows brake fluid reservoir pointed by red arrow. Smaller reservoir is for the clutch.

Clean outside reservoir with water, the reservoir is watertight and can be sprayed with water. Open the reservoir cap, the cap on some vehicles have two parts. In the photo below shows the tank cap is opened and still another cap on the inside.

Open the inside cap and attach to the outer cap. The inside cap prevents brake fluid to spill out but still allow air to enter or ventilation. Below photo shows the inside cap is attached to the outside cap. Note the clear Prestone brake fluid inside reservoir. Clear brake fluid will be replaced with a new red coloured brake fluid. Shown also in the photo the brake fluid is around the maximum level. 

Jack and remove the farthest front wheel from the master cylinder, the left front wheel for Indonesia. Make sure the jack is securely positioned. Put the removed wheel under the car and add a block of wood to help jack. As the photos below.

Check for any trace of brake fluid, which indicates a leak and usually happen in piston caliper, nipple, and brake line connection. 

Clean the left front brake and wheel well with water for easy and clean job. Shown in the photo below the front brake of disc type. On some vehicles the front brake is drum type, especially on the old car, bus and pickup truck.

The air bleeding valve is designated by red arrow in the picture above. Located on the inner side of the caliper, its rubber dust cap was removed to show the nipple.

Loosen the air bleeding valve with combination spanner. The front brake of this vehicle is using combination spanner of size 10 mm, use the one that suit your vehicle nipple. Avoid using an open end spanner to loosen and tighten the nipple, because open end spanner only holds two corners of nipple bolt head and can cause damage to nipple bolt head. In the photo below we can see how to loosen the nipple with ring part of combination spanner, the ring spanner holds to all corners of the bolt head nipple and prevent to damage bolt head.

No need to remove nipple, only loosen nipple to about 30 to 60 degrees of rotation. Usually there will be a drop of brake fluid if nipple is loosened to about 30 to 60 degrees of rotation. Tighten slightly to stop brake fluid drip as it needs to wait for the preparation and installation of hose and used fluid container.

Connect a transparent hose diameter 3/16 inch or 5 mm to nipple, as shown below. If the hose too small, it can be widened a little bit by heat in order to fit it to nipple. If the hose too big, then use a smaller rubber hose. As far as I know the smallest diameter of transparent hose is 3/16 inches. There are rubber hoses with smaller diameter, and rubber hose is far more flexible then plastic hose. But the rubber hose is not transparent so we cannot see and check if any air bubbles inside the hose. So if the nipple is too small, connect a rubber hose to nipple, and then connect that rubber hose to a transparent plastic hose. This way we can clearly see and check fluid inside the transparent plastic hose.

At a distance of about 50 cm from the end of the hose on nipple, tie a yarn. This yarn attached to the vehicle body with duct tape (adhesive tape) to make a loop The higher hose loop peak, the easier for air to come out of hydraulic system as air in brake fluid try to go up to higher place. The yarn does not block the view when we look at top of the hose where air bubbles are gathered. The other end of the hose is inserted into a container. Make sure the hose is not leaking. Leaking hose will allow air to enter the hydraulic system. A leaky hose can also spray brake fluid and damage car paint. Immediately flush with clean water if the paint sprayed with brake fluid.

In the picture above shows a hose is connected to nipple, hose goes up as it is hung by yarn and duct tape on the car body. The other end of the hose is inserted into a container of mineral water plastic bottle, make sure this hose end reach the bottom of container. As container is filled by used brake fluid, fluid will prevent air to get into transparent hose via container. This will ensure only air from hydraulic system gathered at top hose, this way it will be easier to check if there is still air in hydraulic system. Although air may enter hose via container, it can't reach nipple as air can't go down passing through brake fluid by itself. We can see air bubbles from hydraulic system will be gathered at top of the hose, nothing air from container, then air is pushed by pedal pressure down into container.

That rised hose will help to remove air bubbles from brake hydraulic system. Air, steam and other gases have physical properties that lighter specific gravity then liquids. Air, steam, and other gases in the hose will tend to go up to higher place when enter the hose together with brake fluid. So the air, steam and gases will 'go up by themselves' to get out of the brake hydraulic system.

Actual length of the hose is not necessarily the same length as the photo above. Since I will use that hose for other purposes, then I do not cut the hose.

To prevent outside air to enter the brake hydraulic brake system through some small holes (pores) around nipple, then apply grease around nipple and at the end of the hose that is attached to the nipple. See the photo below, green grease is pointed by green arrow. Seen also clear brake fluid had started out with some air bubbles, because nipple has been already loosened again about 30 to 60 degrees shortly before being photographed.

Clear brake fluid will be drained and replaced with red brake fluid. If there are air bubbles in the hydraulic system, the brake fluid in the hose will appear foamy or bubbly. Air bubbles will also be seen moving up as they try to get to a higher place in the hose. Ensure enough fluid in brake reservoir, top up with new brake fluid. The photo below shows Prestone red brake fluid is added. The red brake fluid is over maximum level. But because it will be drained, then the brake fluid level will be lowered by itself.

Get into the cabin and sit on the driver's seat. Make sure the parking brake is released, so that all brake wheel cylinders will react when you step on the brake pedal, and release the trapped air and dirt in the wheel cylinder. Press or pump the brake pedal 5 times, the pedal stroke is long as brake fluid and air go out of loosened nipple. No need to turn on the engine, as foot pressure is enough to pump the pedal. No need to open and close nipple many times.

If the brake fluid has not come out, loosen nipple again to about 30 degrees. Too loose nipple will cause too much brake fluid draining and emptying the reservoir, also causes the air easily enter from the gap around nipple thread.

After 5 times pumping the pedal, check brake fluid in reservoir tank, top up if it has reached a minimum level. Check nipple, hose and used brake fluid container on the wheel brake. Make sure there is no leak in the hose, especially on the connection between the hose to nipple. Fix hose connection and add grease if there are drops of brake fluid.

If everything is no problem, then move on and pump the brake pedal as much as 10-15 times. Do not do it in a hurry. Too many pumping will cause brake fluid reservoir empty and the master cylinder will suck air. Any air inside master cylinder will cause longer time to bleed the system.

For a sedan, usually 50-100 times pumping brake pedal is enough for each wheel to drain the old brake fluid and replace with new fluid. For air bleeding may need a little more pumping, especialy after major repair to master cylinder. Because air inside master cylinder must travel into all pipes and enter into wheel cylinders before it can get out of the brake hydraulic system.

The photo below shows the brake fluid after brake pedal pumped few times. Visible in the transparent hose, clear brake fluid with air bubbles go out first. Brake fluid and air can not re-enter the nipple and come into the wheel cylinder as there is a valve mechanism in the master cylinder that makes the master cylinder works like piston pump. 

Then the brake fluid is changed to red. Different color brake fluid is used to to distinguish the old brake fluid from new brake fluid.

When brake fluid has been replaced with new one, shut nipple off with an open end spanner. Do not too tight as it can damage nipple bolt head.

Remove the hose and retighten nipple with ring part of combination spanner, do not too tight because it gets seized and difficult to be loosen in the future. Brake fluid will seal any small holes (pores) to prevent seepage, after sometime nipple will be more tightened like glued. Photo below shows nipple is tightened with a ring spanner, which is the ring part of spanner is used to tighten the nipple.

Put the dust rubber cap on nipple, clean and wipe all parts and area moistened and dripped by brake fluid. Cleaned and dried area will help to spot any fluid leaks. Reinstall wheel, and lower the jack. Do not forget to tighten wheel nuts criss-cross to ensure wheel is really centrist.

The following video shows brake fluid in the hose. At first clear Prestone brake fluid and many bubbles are going out, followed by Prestone red-colored brake fluid. At the end of the video shows nipple is closed by open end spanner. If you can not open this video, please open it on YouTube: Front Brake Bleeding By Only One Mechanic.

Proceed to the second farthest front wheel from brake master cylinder position, it is the right front wheel for cars in Indonesia. Run test your vehicle and brake suddenly to ensure brakes performance. Pedal will feel higher if the air and the old brake fluid are drained away, and do not feel like stepping on soft foam or baloon.

Used brake fluid should not be recycled, because dirt and water can change the nature of brake fluid, although the visual look is still clean. Because brake fluid also functions to clean the hydraulic system, the brake fluid is made to have same chemical properties as soap. It can dissolve the dirt and water, so it can not be filtered. Old brake fluid can be used as component cleaner, particularly components made of plastic and rubber that are not oil resistant.

Do not dispose carelessly as brake fluid can contaminate the environment, if swallowed in large quantities can be harmful to health.


Your positive comment will be highly appreciated to improve this site