How to: Properly bleed brakes

[metalmonkey47]

How to Bleed Brakes – The Right Way
by John Comeskey of SPS and James Walker, Jr.of scR motorsports

The role of the brake fluid within the braking system is to transfer the force from the master cylinder to the corners of the car…and a vital characteristic of brake fluid that allows it to perform its task properly is its ability to maintain a liquid state and resist compression. In order to keep the fluid in top condition, many enthusiasts have been taught to “bleed their brakes” but many have never stopped to ask the question “why?”

Why Bleed the Brakes?
The term "bleeding the brakes" refers to the process in which a small valve is opened at the caliper (or wheel cylinder) to allow controlled amounts of brake fluid to escape the system. (When you think about it, "bleeding" may appear to be a somewhat graphic term, but it aptly describes the release a vital fluid.)

We bleed the brakes to release air that sometimes becomes trapped within the lines. Technically, "air" only enters the lines if there is a compromise of the system's sealing (as when flex lines are removed or replaced), because when fluid boils, it will instead create "fluid vapor." Vapor in the brake fluid, like air, will create an efficiency loss in the braking system. However, for the sake of simplicity we use the term "air" throughout this article to describe both air and fluid vapor.

When air (or vapor) becomes present within the lines, it creates inefficiencies within the system because, unlike liquid, air can be compressed. So when enough air fills the lines, input at the pedal merely causes the air to compress instead of creating pressure at the brake corners. In other words, when air is present within the system, the efficiency and effectiveness of the braking system is reduced. Usually, a small amount of air within the brake system will contribute to a "mushy" or "soft" pedal (since less energy is required to compress the air than is required to move fluid throughout the brake lines.) If enough air enters the brake system, it can result in complete brake failure.

So how does air enter the lines in the first place? Sometimes, it can be the result of a service procedure or an upgrade – such as replacing the stock flex lines with stainless steel braided lines. But often it is the result of high temperatures that cause brake fluid components to boil, thus releasing gasses from the boiling fluid into the brake hydraulic system.
 

Brake Fluid Selection
This leads one to contemplate the type of liquid that is used as brake fluid. In theory, even simple water would work – since, being a liquid, water cannot be compressed. However, it is important to remember that the fundamental function of the braking system is to convert kinetic energy into heat energy through friction. And the reality of this process is that certain parts of the braking system will be exposed to very high temperatures. In fact, it is not uncommon to see rotor temperatures during a race as high as 1200 degrees Fahrenheit – which can raise the temperature of the brake fluid to well over 300 degrees Fahrenheit. Since the boiling point of water is 212 degrees Fahrenheit, it is easy to see that water within the brake system could boil easily – and therefore release gases into the brake pipes – which would reduce the efficiency of the system. (Water would also present a big problem in cold weather if it froze to ice!)

The "obvious" solution to this problem is to utilize a fluid that is less sensitive to temperature extremes. Hence the development of "brake fluid." However, there unfortunately is no such thing as a "perfect" brake fluid. And like most things in the world, the addition of certain beneficial characteristics usually brings tradeoffs in other areas. In the case of brake fluid, we generally must balance the fluid's sensitivity to temperature against its cost and its impact upon other components within the system.

Stated more bluntly, it is possible to reduce a fluid's sensitivity to temperature by varying the ingredients of the fluid. However, certain combinations of ingredients can significantly increase the cost of the fluid and may react with OEM materials to damage seals and induce corrosion throughout the braking system.

The chemical composition and minimum performance requirements of the fluid are generally indicated through a rating such as "DOT3," DOT4," or "DOT5." The DOT-rating itself is assigned after a series of government tests. However, this rating is NOT intended to indicate boiling points, even though higher DOT ratings generally do correspond with higher boiling points. Perhaps more importantly, the DOT rating does indicate the base compound of the brake fluid - which allows manufacturers to specify fluid types which are less likely to react negatively to known materials used within a particular braking system.

The greatest irony about brake fluid, however, is the fact that the chemical compositions that tend to be less sensitive to temperature extremes also tend to attract and absorb water! So even though the fluid itself is unlikely to boil (most glycol-based DOT3 fluids have a "dry boiling point" around 400 degrees Fahrenheit,) the water that it absorbs over time tends to boil easily (at 212 degrees Fahrenheit.) It is this characteristic of absorbing moisture that leads to the measure known as the "wet boiling point." The wet boiling point is the equilibrium boiling point of the fluid after it has absorbed moisture under specified conditions. Because brake fluid will absorb moisture through the brake system's hoses and reservoir, evaluation of the wet boiling point is employed to test the performance of used brake fluid and the degradation in it's performance. (And it is why we still need to bleed the brakes frequently on racecars, even though we use racing fluid that costs upwards of $75 per bottle!) The lesson: do NOT expect to avoid bleeding your brakes just because you bought expensive brake fluid.

As one might guess, "racing" fluids will use relatively "aggressive" chemical compositions which will tend to have higher wet boiling points and higher costs, while the average street fluids will use more conservative compositions which will have lower wet boiling points and lower costs. In some cases – such as a purpose-built racecar – the tradeoffs of using the expensive racing fluid is outweighed by the competitive advantages. But for the average driver – whose driving style is less likely to induce brake temps as high as those seen on the track – the costs of the fluids and potential wear-and-tear factors upon system components may justify the use of a more conservative fluid with a lower wet boiling point.

How-To
So, now that you understand the need behind bleeding your brakes, let us present just one procedure that can be utilized when servicing your own car. Note that unless you are replacing your master cylinder, the procedure is the same whether you have a vehicle equipped with ABS or not…

Supplies Required
You will need the following tools:
-Box-end wrench suitable for your car's bleeder screws. An offset head design usually works best.
-Extra brake fluid (about 1 pint if you are just bleeding, about 3 if you are completely replacing).
-12-inch long section of clear plastic tubing, ID sized to fit snugly over your car's bleeder screws.
-Disposable bottle for waste fluid.
-One can of brake cleaner.
-One assistant (to pump the brake pedal).

Vehicle Preparation and Support
1. Loosen the lug nuts of the road wheels and place the entire vehicle on jackstands. Be sure that the car is firmly supported before going ANY further with this procedure!
2. Remove all road wheels.
3. Install one lug nut backward at each corner and tighten the nut against the rotor surface. Note that this step is to limit caliper flex that may distort pedal feel.
4. Open the hood and check the level of the brake fluid reservoir. Add fluid as necessary to ensure that the level is at the MAX marking of the reservoir. Do not let the reservoir become empty at any time during the bleeding process!

Bleeding Process
1. Begin at the corner furthest from the driver and proceed in order toward the driver. (Right rear, left rear, right front, left front.) While the actual sequence is not critical to the bleed performance it is easy to remember the sequence as the farthest to the closest. This will also allow the system to be bled in such a way as to minimize the amount of potential cross-contamination between the new and old fluid.
2. Locate the bleeder screw at the rear of the caliper body (or drum brake wheel cylinder.) Remove the rubber cap from the bleeder screw – and don't lose it!
3. Place the box-end wrench over the bleeder screw. An offset wrench works best – since it allows the most room for movement.
4. Place one end of the clear plastic hose over the nipple of the bleeder screw.
5. Place the other end of the hose into the disposable bottle.
6. Place the bottle for waste fluid on top of the caliper body or drum assembly. Hold the bottle with one hand and grasp the wrench with the other hand.

7. Instruct the assistant to "apply." The assistant should pump the brake pedal three times, hold the pedal down firmly, and respond with "applied." Instruct the assistant not to release the brakes until told to do so.
8. Loosen the bleeder screw with a brief ¼ turn to release fluid into the waste line. The screw only needs to be open for one second or less. (The brake pedal will "fall" to the floor as the bleeder screw is opened. Instruct the assistant in advance not to release the brakes until instructed to do so.)
9. Close the bleeder screw by tightening it gently. Note that one does not need to pull on the wrench with ridiculous force. Usually just a quick tug will do.
10. Instruct the assistant to "release" the brakes. Note: do NOT release the brake pedal while the bleeder screw is open, as this will suck air back into the system!
11. The assistant should respond with "released."
12. Inspect the fluid within the waste line for air bubbles.
13. Continue the bleeding process (steps 11 through 16) until air bubbles are no longer present. Be sure to check the brake fluid level in the reservoir after bleeding each wheel! Add fluid as necessary to keep the level at the MAX marking. (Typically, one repeats this process 5-10 times per wheel when doing a ‘standard' bleed.)
14. Move systematically toward the driver – right rear, left rear, right front, left front - repeating the bleeding process at each corner. Be sure to keep a watchful eye on the brake fluid reservior! Keep it full!
15. When all four corners have been bled, spray the bleeder screw (and any other parts that were moistened with spilled or dripped brake fluid) with brake cleaner and wipe dry with a clean rag. (Leaving the area clean and dry will make it easier to spot leaks through visual inspection later!) Try to avoid spraying the brake cleaner DIRECTLY on any parts made of rubber or plastic, as the cleaner can make these parts brittle after repeated exposure.
16. Test the brake pedal for a firm feel. (Bleeding the brakes will not necessarily cure a "soft" or "mushy" pedal – since pad taper and compliance elsewhere within the system can contribute to a soft pedal. But the pedal should not be any worse than it was prior to the bleeding procedure!)
17. Be sure to inspect the bleeder screws and other fittings for signs of leakage. Correct as necessary.
18. Properly dispose of the used waste fluid as you would dispose of used motor oil. Important: used brake fluid should NEVER be poured back into the master cylinder reservoir!

Vehicle Wrap-Up and Road Test
1. Re-install all four road wheels.
2. Raise the entire vehicle and remove jackstands. Torque the lug nuts to the manufacturer's recommended limit. Re-install any hubcaps or wheel covers.
3. With the vehicle on level ground and with the car NOT running, apply and release the brake pedal several times until all clearances are taken up in the system. During this time, the brake pedal feel may improve slightly, but the brake pedal should be at least as firm as it was prior to the bleeding process.
4. Road test the vehicle to confirm proper function of the brakes. USE CAUTION THE FIRST TIME YOU DRIVE YOUR CAR AFTER MODIFICATION TO ENSURE THE PROPER FUNCTION OF ALL VEHICLE SYSTEMS!

How Often do I Need to Bleed My Brakes?
In closing, here are a few rules of thumb to help you to determine the proper bleeding interval for your particular application:

1. Under normal operating conditions, and without brake system modifications, typical OEM braking systems have been designed to NOT require bleeding for the life of the vehicle unless the system is opened for repair or replacement. If you're just driving around town or on the highway to work, there is really no need to bleed! There are a few European vehicles which do recommend replacement on a semi-regular basis for other reasons though, so be sure to check in your owner's manual or at your service center for your particular application.

2. Those who choose to autocross or drive in a sporting manner may choose to upgrade their brake fluid and bleed on an annual basis – this is a good ‘start of the season' maintenance item for low-speed competitors.

3. If your car sees significant amounts of high-speed braking, or if you choose to participate in driver schools and/or lapping sessions, bleeding prior to each event is a sound decision. More intense drivers at these events may choose to skip right past this step and on to #4…

4. Finally, dedicated race cars should be bled after every track session.






ALL info above provided by the great techs @ Stoptech.

Edited July 27, 2016 by metalmonkey47

[Eagle_Adam]

great info!!! :D

[datzenmike]

If you have never replaced the brake fluid in your vehicle.... it's time. I have never heard that they last the life of the vehicle, but I would do it every 3-5 years. The fluid in the reservoir may look fine or cloudy with moisture but how can you tell what the fluid is like inside the calipers where it is subjected to years of high temperature braking??? Flushing will remove any water or contaminants. Water is the worst enemy of the braking system. (it boils at only 212F / 100C. Brake fluids boil is, at a minimum, twice that amount)

 

If the system is old and has not been serviced, expect to snap off a frozen bleeder off and be prepared for this with new brake cylinders. This is the price you pay for a properly functioning braking system. Once in shape, yearly checks will keep it this way. Remember, the braking system is the single most important safety device in your vehicle. More important than a padded dash, air bags, seat belts, head rests.

[jboulukos]

If you have never replaced the brake fluid in your vehicle.... it's time. I have never heard that they last the life of the vehicle, but I would do it every 3-5 years. The fluid in the reservoir may look fine or cloudy with moisture but how can you tell what the fluid is like inside the calipers where it is subjected to years of high temperature braking??? Flushing will remove any water or contaminants. Water is the worst enemy of the braking system. (it boils at only 212F / 100C. Brake fluids boil is, at a minimum, twice that amount)

 

If the system is old and has not been serviced, expect to snap off a frozen bleeder off and be prepared for this with new brake cylinders. This is the price you pay for a properly functioning braking system. Once in shape, yearly checks will keep it this way. Remember, the braking system is the single most important safety device in your vehicle. More important than a padded dash, air bags, seat belts, head rests.

 

I last had my brakes checked in 2009 when I purchased my B210.  They rebuilt the front calipers and installed new pads and caliper seals.  The receipt says "inside of caliper was plated and plating was peeling off, bore was honed best as possible, suggest finding a core set of calipers and having them rebuilt with sleeves if necessary."  

 

Since then, I have probably put 20K miles on the car.  I am definitely in need of some overhauling of the brake system.   The brakes seem to be getting very very poor.  I understand the fluid should be bled every few years and not 6-7 years like mine.  I'm reading the Chilton, Clymer and service manual books to learn.  I also have a NOS Nabco master cylinder.  

 

My main question is where to start?  I certainly will examine the pads and I know that it will be smart to bleed the entire system.  Should I start with new front pads and calipers, and rear shoes?  Would you recommend that I just install the new master cylinder as well?  Would you recommend trying to obtain original calipers?  Do you recommend any particular brand of pads and shoes?  

Basically need to make a RockAuto order.

 

As always, any information is much appreciated.

[datzenmike]

If the calipers are not leaking replace the pads but get the rotors turned, or if too far to do properly, replace them too. If able to, replace the calipers but the biggest wear item are the pads and rotors.

 

Replace the rear shoes but again have the rear drums turned to true them up. If too worn replace them also or get a good used set that can be turned.

[jboulukos]

If the calipers are not leaking replace the pads but get the rotors turned, or if too far to do properly, replace them too. If able to, replace the calipers but the biggest wear item are the pads and rotors.

 

Replace the rear shoes but again have the rear drums turned to true them up. If too worn replace them also or get a good used set that can be turned.

 

Are aftermarket calipers fine or should I try to find NOS or remanufactured ones?

Besides new pads/shoes, rotors and drums replaced/turned, and calipers replaced....are there any other components to purchase?  Brake fluid and grease.

[datzenmike]

I doubt you will find NOS calipers. To be NOS it would have to be found siting on a shelf at a Nissan dealer, never sold. Next would be a set bought and never used, still sealed and in it's original packaging with it's bill of sale. You see... NOS is a myth, but people will tell you it's NOS and charge you an extra $100 for it if you let them.

 

A reputable re manufactured set are ok. (get guarantee and keep receipt) For a few bucks you can get rebuild kits if, and only if, the castings and pistons are not rusty inside. I went through 3 sets of 4 piston Toyota 4x4 calipers to find a clean set. Rebuilt them for about $18 each. They provided years of trouble free braking and are probably still doing so.  

[Charlie69]

I have been buying rebuilt "loaded" calipers from Rock Auto for years.  I have been buying closeouts for my Datsun/Nissan trucks and get a pair of rebuilt "loaded" calipers for $47.89 plus shipping on closeout.  These are Morse rebuilt calipers.  I have had 1 left caliper piston freeze and destroy the caliper and rotor in the 7 years..  The freeze was caused by a kinked steel brake line, no fault of the caliper or rebuilder.

 

[jboulukos]

I doubt you will find NOS calipers. To be NOS it would have to be found siting on a shelf at a Nissan dealer, never sold. Next would be a set bought and never used, still sealed and in it's original packaging with it's bill of sale. You see... NOS is a myth, but people will tell you it's NOS and charge you an extra $100 for it if you let them.

 

A reputable re manufactured set are ok. (get guarantee and keep receipt) For a few bucks you can get rebuild kits if, and only if, the castings and pistons are not rusty inside. I went through 3 sets of 4 piston Toyota 4x4 calipers to find a clean set. Rebuilt them for about $18 each. They provided years of trouble free braking and are probably still doing so.  

What material would you recommend for front pads?  (ceramic, organic, semi-metallic)  I have the honeycomb wheel covers so access the rinsing/cleaning is less.  I figured a ceramic or organic in order to have less dust...

[Lockleaf]

Organics are not worth the effort. Get ceramics.

[jboulukos]

I have been buying rebuilt "loaded" calipers from Rock Auto for years.  I have been buying closeouts for my Datsun/Nissan trucks and get a pair of rebuilt "loaded" calipers for $47.89 plus shipping on closeout.  These are Morse rebuilt calipers.  I have had 1 left caliper piston freeze and destroy the caliper and rotor in the 7 years..  The freeze was cause buy a kinked steel brake line, no fault of the caliper or rebuilder.

 

Thanks for adding to my knowledge.  I looked on RockAuto... for 1978 B210, they have a loaded Beck/Arnley for $30.79.  Also, there are "semi-loaded" rebuilt ones which use original caliper cores.  When it comes to brake calipers, would getting an original core be of any significance/benefit?  

[jboulukos]

Organics are not worth the effort. Get ceramics.

Point taken.  Great to get this info because I know jack about this.  Watched a 2 minute youtube video with a guy briefly explaining the differences in a very vague way.  I will get ceramics!

[jboulukos]

If the calipers are not leaking replace the pads but get the rotors turned, or if too far to do properly, replace them too. If able to, replace the calipers but the biggest wear item are the pads and rotors.

 

Replace the rear shoes but again have the rear drums turned to true them up. If too worn replace them also or get a good used set that can be turned.

 

Seems like both rotors and drums for the B210 are cheap enough to buy new instead of paying for turning/resurfacing which may amount to higher labor cost with more wear on the part.

[Charlie69]

I believe all re-built calipers are from genuine cores.  I think this is what they cal in advertising a "hook."

 

I buy new drums and rotors from Rock Auto cheaper than I can have rotors and drums turned.

[datzenmike]

Often the case. Had a Dodge Omni. The rotors were $18 to turn each, but only $20 new. Duh.

 

Pad material choice can increase rotor wear too. Its a trade off.

 

Dust is not a problem really and it doesn't need cleaning every week. It builds up over time. The wheel discs easily pop off for cleaning and I used to polish them with car wax so it comes off easier. This was '76 so they probably have stuff for this now.

[Dolomite]

You can bleed your brakes by yourself without any specialty tools. Put a bit of brake fluid in your waste bottle, enough to cover the end of the tube from the bleeder is enough. Now open the bleeder and slowly depress and release brake pedal. Keep an eye on your reservoir so you don't drain it too far. Top off reservoir and pump fluid through until you see no bubbles in the tubing within a few inches of the bleeder. Repeat for each corner...enjoy safe braking.

[jboulukos]

At this point, I am trying to visualize the order of events to change the components of the brakes, add the new master cylinder and bleed/re-fill the entire system.

I'm going to obtain some jack stands first. Then make the RockAuto parts order.

Once everything is in place, I'll do the job.

 

 I like to make a list/order of events to follow so I can be successful. 

 

1. Car on 4 jack stands with wheels removed

2. Rear Drums and Shoes replaced and adjusted*

3. Front Rotors, Calipers and Pads replaced

4. Remove old master cylinder and replace with new

5. Completely bleed all 4 lines

6. Add new Dot 3 brake fluid and bleed each brake in sequence

7. Wheels on, car lowered and test drive

 

Questions

* Do the rear drums get adjusted when hot? If so, how/when?

Do I want to use brake grease anywhere?  back side of pads?

Do I need 4 jack stands to do this properly? 

 

Is my order correct?  Anything else to take into consideration?  I'm a layman with this so I want to get my planning and understanding right.  

[Dolomite]

2 things...you don't NEED 4 jackstands, bench bleed master cylinder first.

[jboulukos]

2 things...you don't NEED 4 jackstands, bench bleed master cylinder first.

I'm going to ask for layman specifics.  Explain "bench" bleed por favor.

 

Do I need 2 jackstands even?  Or just jack up each tire as I go from one to another?

[Dolomite]

I usually just do one at a time. Its probably easier to Google or YouTube bench bleeding, there'll be visual aids. It involves filling reservoirs and gently depressing and releasing the piston until bubbles stop being released into the reservoir.

[jboulukos]

I usually just do one at a time. Its probably easier to Google or YouTube bench bleeding, there'll be visual aids. It involves filling reservoirs and gently depressing and releasing the piston until bubbles stop being released into the reservoir.

Sweet.  I'll look it up.  So basically bleed each brake line first, then change out the master cylinder? Then go back to each brake and change the components and bleed again?

[Rick-rat]

Bench bleed the Master Cylinder first, and install. Then bleed the brakes

[jboulukos]

Bench bleed the Master Cylinder first, and install. Then bleed the brakes

 

Fantastic.  Just found a few good videos on bench bleeding the master cylinder.  I'll pick up a bench bleed kit.  

A few questions:

 

-after bench bleeding the new master cylinder, how do I remove the old master cylinder without making a mess with the fluid?  

[datzenmike]

At this point, I am trying to visualize the order of events to change the components of the brakes, add the new master cylinder and bleed/re-fill the entire system.

I'm going to obtain some jack stands first. Then make the RockAuto parts order.

Once everything is in place, I'll do the job.

 

 I like to make a list/order of events to follow so I can be successful. 

 

1. Car on 4 jack stands with wheels removed

2. Rear Drums and Shoes replaced and adjusted*

3. Front Rotors, Calipers and Pads replaced. When you press the caliper piston back into the cylinder in order to get the new thicker pads on the new thicker rotor, the fluid in the calipers will be pushed back into the master reservoirs. If the reservoirs have been topped up... they will overflow, so have something handy to catch and absorb this. May happen on the rear cylinders.

4. Remove old master cylinder and replace with new

5. Completely bleed all 4 lines Use new DOT fluid

6. Add new Dot 3 brake fluid and bleed each brake in sequence

7. Wheels on, car lowered and test drive

 

Questions

* Do the rear drums get adjusted when hot? If so, how/when? No adjust when replaced is fine. After any adjustment pump the brakes to center the sliding adjuster and check/adjust again. MAKE SURE you back the E brake off first... adjust it LAST.

Do I want to use brake grease anywhere?  back side of pads? Absolutely not. Special grease can be applied sparingly to any rubbing sliding parts on the rear drums. (see manual) Some front calipers self adjust side to side and need a small amount of grease on the rubbing points. You will have to find out where these points are. 

Do I need 4 jack stands to do this properly? If you have them. You can get by with only two

 

Is my order correct?  Anything else to take into consideration?  I'm a layman with this so I want to get my planning and understanding right.  

[Genaro]

 

Once i replaced the fluid myself by pushing new fluid with a really big syringe from each purge plug... i didnt have any proper helper available at the moment.

 

Of course, i did emptied (almost) the reservoir after each wheel.

 

i dont think it is an usual or correct method, but it worked out pretty well, brakes kept working the same as before.