Contents

1. Introduction
2. Parking Brake Test
3. Bleeding Brakes
4. Flushing The Brake System
5. One Way Valves
6. The Solution
7. Make A Checklist
8. Master Cylinder Sediment
9. Differences Between Antiques and Everyday Work Cars
10. Brake Line Sediment
11. Summary
12. Conclusions
13. Links
14. Questions and Comments
15. Updates
16. Patents and Copyright

Introduction

Of all the systems in a vehicle, the brakes are by far the most important. A crack or leak in the system could cause loss of pressure and result in complete brake failure.

Parking Brake Test

You can see what this means by finding a road with no traffic, slowing to 10 mph, and trying to stop the car using the parking brake. (Make sure no one is behind when you apply the parking brake, since there will be no brake lights to warn the driver you are slowing.)

The results can be alarming. You may find the parking brakes have very little effect even when they are working properly.

Your life, and the safety of others, may depend on stopping the vehicle when you need to. Regular bleeding and flushing is needed to ensure top performance from your brake system.

Bleeding Brakes

In 1918, a young inventor named Malcolm Lougheed (who later founded Lockheed Aircraft Company) developed the first hydraulic brakes for cars. This led to the problem of air in the brake lines, and how to remove it.

In this article, we show how to solve this century-old problem.

The classic method to bleed air from the brakes is to find someone to push on the brake pedal while you open and close the bleed screw. This is called the Pump and Hold method, since you have to tell your assistant when to push and when to release the pedal as you open and close the bleed screw.

Here is a short video that illustrates this method (1min, 48sec). There are many simliar ones on the web.

There are a number of problems with this method. 1) Finding an assistant can be difficult. 2) Pushing on the brake pedal is fatiguing. Your assistant will quickly tire, and start to make mistakes. 3) It is easy to make a mistake and lift the pedal while the bleed valve is still open. This can let air back into the cylinder so you have to start over again. 4) Due to the frequent movement, the bleed hose may loosen or fall off while you are adjusting the bleed screw. This can let air into the cylinder, and you have to start over again. 5) When you have finished bleeding all four wheels, you may find the brakes are still soft. You don't know which wheel still has an air bubble, so you have to bleed them all again. 6) The entire process is slow and prone to error, and can take a long time when you have to bleed all four wheels.

A friend in Australia wrote a quick note that summarizes the frustration that can occur when you are trying to bleed the brakes in the conventional fashion:

But I can't wait to try out this idea next time I do the brakes, as it's always a pain to have to shout:

"Down... Up... No, I said up... Thanks... Now down again... No, you're doing a great job. Is the pedal down now?" etc., etc.

Flushing The Brake System

The DOT3 and DOT4 brake fluid used in most cars will absorb moisture. This can lead to corrosion problems, and mechanics often recommend to flush the system regularly. Also, the rubber used in seals and flexible brake hose degrades with time and wear, which turns the brake fluid black. This is a good time to flush the system, since the debris can settle in the master cylinder and other critical components and add to the corrosion problems.

Flushing the system with an assistant is impractical, since it may take hundreds of open and close cycles to completely remove the old fluid. Automotive shops have special equipment to do the job faster, but their charges can be quite high. This often means the brakes are not flushed until major repairs are needed. Some of these may be caused by corrosion from the old, contaminated brake fluid.

One Way Valves

Speed Bleeder Products, Inc adds a one-way check valve in the bleeder screw so you don't have to keep opening and closing it while your assistant pumps the brakes.

The steel screws are $7.00 each, or $28.00 for a set of four. These will rust and may not work the next time you go to use them. Stainless versions are available for $15 each, or $60.00 for a set of four.

These seem to be an excellent idea, but they are very expensive for such a simple task.

The Solution

The above problems can be eliminated with a simple device that costs only pennies, and can be made in minutes.

Here's how.

Pick one or two that you like and give the rest to your friends so they can make their own balloon valve.

We need to cut the end of the bleed hose so it is square. Get a fresh, sharp section of blade in your knife.

The method shown on the right is doomed to failure. The hose will prevent you from pushing the knife completely through, so you end up sawing and hacking your way through. The cut will have several edges and not seal properly.

This allows the end of hose to drop away, giving room for the knife blade to pass through.

We will test the cut to make sure it works satisfactorily.

When you are satisfied the valve is working properly, wrap some electrical tape around the open end of the balloon to hold it in place.

When you press on the brake pedal, the pressure will lift the balloon off the end of the hose and allow the brake fluid to flow into the collection bottle. But it can only flow in one direction, since the balloon valve will close when you release the pressure.

When you release the pedal, the balloon will rest against the end of the hose and prevent air and fluid from flowing back into the cylinder.

The balloon valve closes automatically, so you no longer need someone to push on the brake pedal while you close the bleed screw.

This solves the century-old problem of bleeding air from the brakes.

Apply a thin coat of antiseize compound to the threads, then wrap 4 to 6 turns of Teflon tape around the threads. This will prevent air from entering via the threads. A sharp-eyed reader in Australia noticed that I have wound the tape against the thread pitch. This is the wrong direction, but it takes a much better photo than winding it in the correct direction. You may wish to wind it the other way for your work.

Insert the bleed screw in the cylinder and tighten so it just begins to seal. Loosen 1 turn or more to allow brake fluid to pass through freely.

If the hose leaks air at the bleed screw, use ordinary vaseline to seal the gap around the bleed screw.

Clean the area around the master cylinder to keep dirt out.

Use a spray pump to remove old fluid from the master cylinder reservoir so you don't have to pump it through the lines. Fill the reservoir with new fluid.

Use a clean funnel to keep brake fluid away from painted surfaces since it will remove the paint. Wash the area with plenty of water if needed.

Have your assistant monitor the level and tell you when more fluid is needed.

If you don't have an assistant, count the number of pedal pushes it takes to drain half the fluid. Add 50% and check the fluid level when you reach this count.

For example: If it takes 12 pedal pushes to empty half the fluid, stop when you reach a count of 12+12/2=18, then refill the master cylinder.

Keep the lid on at all times when you are not filling the reservoir. This helps prevent dirt and debris from falling in.

The white material on the face of the drum is Permatex 133h Antiseize Lubricant. This keeps the drum from rusting and corroding the aluminum alloy wheel.

Use two bottles and work back and forth so you can tell when the fresh fluid starts to appear. After a dozen refills or so, the fluid is starting to turn a clear straw color. You can also check the fluid in the drain hose but it may not be as easy to see the change.

This job would be difficult using the conventional Pump and Hold method, but it is fast and easy with the balloon valve controlling the fluid flow.

Make A Checklist

When you are done, it is a very good idea to have a checklist handy to make sure you have not forgotten anything. Here are some things to look for:

Torque Bleed Screws

1. Tighten the bleed screw before removing the drain hose. If you remove the hose before tightening, you may allow air back in the cylinder.

2. The bleed bolts in brake systems are hollow and easily damaged. Do not overtighten. Use the manufacturer's recommended torque value.

Rubber Plugs

1. Make sure you replace the rubber caps on the bleed screws to prevent them from rusting. This makes them useless for bleeding. It would probably be a good idea to fill the bleeder cap with Sil-Glyde, Permatex Brake Grease, or some other corrosion preventative grease that is compatible with rubber. You need the nipple to stay clean so it will seal properly inside the drain hose.

2. Replace the rubber seals that are needed to close the adjustment holes for the drum star wheel.

Brake Fluid

1. You will find the balloon valve will keep the drain hose full of brake fluid. It will dribble all over the place if you let the end drop. Put the open end in the drain bottle and allow the fluid to drain completely. Be sure to keep brake fluid from touching painted surfaces since it will remove the paint. Wash the area with plenty of water if this happens.

2. Check the fluid level in the Master Cylinder and top off if needed.

Replacing Wheels

1. Replace the wheels and tighten the lug nuts to make sure the wheels are snug against the drum or disk rotor. When you finish one nut, tighten the next one that is furthest away so you have to cross the center of the wheel to get to it. This path forms a star pattern.

2. Make sure the car is safe before jacking it up to remove the jackstands. Ensure nobody is near the vehicle, and the doors are closed so they do not accidentally hang on something as the car settles.

3. Torque the wheel nuts to the proper torque.

4. Check the area carefully to make sure you have not left any tools under the car or out of sight.

Test Brakes

1. Make sure the parking brake works and will stop the car. Review the Parking Brake Test in case it is needed.

2. Ensure the brake pedal will hold foot pressure before starting the engine.

3. Go a short distance in the driveway or parking lot and test the brakes several times with hard stops before taking the car on the road.

4. Once you are confident the brakes are working, open the windows and drive by a long building like Walmart. Listen for reflections of any sounds like tinkling or clicking from underneath the car that might indicate something needs to be checked.

5. When you return from testing the brakes, check the wheel lug nuts again to ensure they are properly torqued and you haven't accidentally missed one.

6. You will be surprised at how often this happens. People drop by to say hello, and before your know it, you have skipped tightening one or more lug nuts. It is definitely worth rechecking. Give yourself 5 stars if you cannot find at least one that is loose.

Regular Maintenance

1. Check the brake fittings and hoses periodically for rust, fluid leaks or damage from stones kicked up by the tires.

2. Monitor the master cylinder reservoir for fluid level and color. The fluid level will drop slowly due to normal brake wear, but check the entire system if you notice any sudden changes in level or color.

3. While you have the hood open, check the rest of the fluids, such as engine coolant, oil level, transmission fluid, washer fluid, power steering, battery, and any other maintenance items that may need your attention.

4. Most sites recommend not storing unused brake fluid, since it can absorb moisture from the atmosphere. This may be a bit conservative. I seal the container in three separate polyethylene bags that have been checked for leaks. This keeps the fluid dry until needed.

Master Cylinder Sediment

Honda Magazine recommends against pushing the brake pedal all the way to the floor:

"Be sure the person pumping the pedal does so no more than halfway to the floor. If it's pushed too far, you run the risk of driving the master cylinder's secondary piston across sediments or deposits that may have collected on the piston cylinder walls. This can permanently and quickly damage piston seals and cause leaks. Place a small block of wood underneath the brake pedal to ensure this doesn't happen."

The url is http://www.hondatuningmagazine...

This precaution is echoed by Sierra Specialty Auto in Quincy, California. They specialize in restoring brake cylinders in heritage autos, and have a fascinating site that documents their methods on antique cars. They have some important information on corrosion:

"From the moment a hydraulic brake component is put into service, moisture begins to attack and pit the cylinder walls, eventually leading to leaks and failure of the component. Master cylinders, wheel cylinders and clutch slave cylinders can become so pitted that they are no longer rebuildable using conventional honing techniques."

http://www.brakecylinder.com/sleeve1.htm

This shows the importance of flushing the system regularly to eliminate moisture that is absorbed in the brake fluid.

Here is more information on low mileage cars:

"Cylinders in cars that get fewer than a few thousand miles per year can be expected to last perhaps 5-6 years before pitting is bad enough to chew up the rubber."

"It's important to note that these systems do not fail from wear but rather from pitting caused by rust or corrosion. Brake parts move so slowly and so seldom, relatively speaking, and are so well lubricated that wear just isn't a factor."

"If we can prevent the pitting, we prevent the failure."

"One important point - limit the travel of the brake pedal if using the pedal to bleed (as opposed to pressure bleeding or vacuum bleeding.) If you allow the piston in a used master cylinder to travel beyond the area of normal travel, the layer of gunk on the cylinder wall can tear up the cups, causing failure of the master shortly after. We put a block or blocks under the brake pedal to hold it about as far off the floor as it is when the brake is applied."

"If you happen to be replacing or rebuilding the master at the same time, so that you know the bore is clean all the way down, this caveat does not apply."

http://www.brakecylinder.com/BrakeFAQ.htm

Differences Between Antiques and Everyday Work Cars

It is important to note the differences between heritage vehicles and normal service cars. First, the gunk that builds up in the master cylinder of an antique car may take decades to accumulate. Service vehicles rarely last that long, and they usually end up in a junkyard after 10 to 15 years. So there is not enough time to build up significant amounts of gunk.

Antique cars are rarely driven, so the absorbed moisture causes corrosion and pitting after 5 to 6 years. In contrast, the brakes on service vehicles usually need replacing every year or two, depending on usage. So the moisture that was absorbed in the old brake fluid is eliminated when the brakes are flushed and new fluid is added.

This means the gunk that can damage master cylinder seals is less likely on everyday service vehicles. For example, the web videos by mechanics on bleeding brakes do not mention the need for limiting the brake pedal travel. It's mainly on the sites that deal with older heritage vehicles.

In fact, using the full pedal travel when bleeding the brakes may actually help by forcing sediment out of the master cylinder and into the collection jar. Removing the sediment means less chance for corrosion since there are fewer nucleation centers for corrosion to start.

So limiting the pedal travel on newer service vehicles may actually harm the system since it leaves the sediments in the master cylinder.

Brake Line Sediment

The vacuum and pressure bleeding systems commonly used are low pressure systems. This means they do not develop the high fluid velocity needed to sweep sediments out of the brake lines.

In contrast, the full pedal travel used in the balloon valve method can take less than a half second. This puts pressure in the lines, which increases the fluid velocity. And you can put a lot more pressure in the line with your leg muscles than with a small hand-operated vacuum pump.

This is why my car has a brake fluid capacity of about 250 ml, but it took over 2 litres of fluid to flush the system, as shown here. The reason is the high fluid velocity from the balloon valve method kept sweeping more sediment from the lines.

This means that passive bleeding methods, such as pressure or vacuum systems, may actually harm the brake system since they leave sediment in the master cylinder and brake lines. These methods are frequently used in automotive repair shops to bleed your brakes, but they can lead to master cylinder failure or brake line corrosion.

Summary

It is important to keep the master cylinder bore and brake lines clean and free of sediments, since these can act as nucleation centers that start the corrosion process. This means a swift, full pedal travel is needed to sweep any sediments out of the brake system and into the collection jar.

The conventional Pump and Hold method previously used is awkward, slow, and prone to error, but the balloon valve method shown here helps eliminate all these problems.

Conclusions

The passive flushing methods, such as vacuum or pressure bleeding, do not develop enough fluid velocity to sweep sediment from the master cylinder and brake lines. The sediment can form nucleation centers for corrosion to start.

The conventional Pump and Hold method previously used is awkward, cumbersome, slow, and prone to error. It may fail to bleed all the air from the lines, and may have to be repeated.

The balloon valve method shown here is fast, inexpensive, and easy to use. It is repeatable, gives high fluid velocity to sweep debris from the system, and helps eliminate the problems of previous methods.

Of all the methods available to bleed and flush brakes, the balloon valve gives the best performance and is the most effective at removing the sediments that can accelerate corrosion.

Links

There are many excellent articles on selecting brake fluids, troubleshooting brake problems, and replacing rotors and pads. Space and time limits do not permit listing them, but google is an excellent resource. A good place to start is the Wikipedia Overview on Brake Bleeding. Also, be sure to read the article on Brake Flushing by Rik Paul. A fascinating site for heritage vehicles is Sierra Specialty Auto in Quincy, California. You can find all sorts of information on how brake systems were made in the old days, and what it takes to keep them working in the present.

Questions and Comments

People from all over the world are coming to visit this page. Thanks! If you have any suggestions on improvements for other visitors, please let me know here

Updates

Before working on your brakes, check for the latest update. The url for this page is http://pstca.com/articles/bleed/balloon.htm

Patents and Copyright

The information and all rights to the balloon method of brake bleeding and flushing is placed in the public domain by Michael R. Monett, on Aug 12, 2010.