Team-BHP - What is Brake bleeding????

i thinks it reefers to getting the air out of the braking system
when you get something done to the brakes like flushing the old brake fuild out and putting the new one in

its done to get the brake pressure back

get the brake pads change
new fluid and get the drums clean

Brake bleeding involves siphoning out all the brake fluid and then refilling the fluid reservoir. Many a times air bubbles get trapped in the fluid. This reduces the efficacy of braking. This happens typically when the fluid is old. Otherwise also it may be necessary when the fluid has lost its viscosity due to continuous braking over a period of time.

Quote:

Originally Posted by rishibravo (Post 483528)

How to figure out whether bleeding is required or my brake pads have worn out?

If your brake pad's are worn out (very badly) you can see scratches on the disc's (if ur vehicle comes with disc brakes) or if its heavily worn you can hear grinding sound due to friction. If there is a grinding sound realise that you are driving on pure luck. :p

At least once every 3000 kms get the pad's checked OR if you feel that the braking distance has increased.

Brake bleeding involves draining the brake fluid, replinishing it with new fluid, checking the brake pad's / shoes, servicing the moving parts etc. I've also observed that the pad's are scrubbed on sandpaper (even when it has quite some life left).

Brake bleeding is the procedure performed on hydraulic brake systems whereby the brake lines (the pipes and hoses containing the brake fluid) are purged of any air bubbles. This is necessary because, while the brake fluid is an incompressible liquid, air bubbles are compressible gas and their presence in the brake system greatly reduces the hydraulic pressure that can be developed within the system. The same methods used for bleeding are also used for purging, where the old fluid is replaced with new fluid, which is necessary maintenance. Note: brake fluid is toxic, and must be handled carefully and disposed of properly.

The process is performed by forcing clean, bubble-free brake fluid through the entire system from the master cylinder(s) to the calipers of disc brakes or the wheel cylinders of drum brakes). The brake bleeder valve is normally mounted at the highest point on each cylinder or caliper.

Bleeding brakes is something that should be done every two years or so to remove contaminated brake fluid. DOT 3 or DOT 4 brake fluid (the kind that's probably in your car's system) is hygroscopic, that is, it absorbs water. The brake lines, master and slave cylinders and fittings on your brake system are made of steel (some after market brake components are stainless steel but Jaguar have never fitted these to any production model of which I'm aware). These will rust in time if exposed to water, setting the stage for catastrophic brake failure. Water will also boil if the brake cylinder gets hot enough, causing brake loss just when you most need the brakes.

The Solution

Brake fluid should be replaced by bleeding at least once every two years. The process of bleeding your brakes is rather straight forward, and can be done by the average home mechanic with a few tools and one assistant.The job involves opening fittings on the calipers called bleeder screws and pumping the old brake fluid out of the lines and replacing it with new. You do this by pushing on the brake pedal and using it as a pump. The trick is to not introduce any air into the system when doing this.

Bleeding is the process of removing the air from the system.

It is not the process of draining or replacing the fluid but will be a necessary task after that has been done.

The pressure involved in the break system is sufficient to cause enough heat so that water droplets turn to steam... and steam is a compressible gas, like air, so breaking power is lost.

Changing the break fluid should be there somewhere on the service schedule.

Quote:

Originally Posted by fiery enzyme (Post 483426)

Hi guys

Sorry if I sound stupid but can somebody explain what is brake bleeding and can you give some tips on how to improve braking performance?.

What are the surrounding factors involved in braking?.

brake bleeding is necessary ONLY if
1) u feel the pedal spongy with loss of braking power and u find the brake master cylinder reservoir empty. if its empty then topping with DOT 3 or 4 wont help as there will be air in the system and this calls for bleeding and refill with new fluid.

This applies to the Clutch also if u find the cylinder empty just refill wont help as occassionally u will find the pedal just going to metal and some pumping will help get the pressure back to atleast help in changing a gear.

2) depends on your driving style usage of brake. A normal flush should be about 5 years, (i have not done one in 5 yrs with over 700k - braking habits) periodic check with a minor top up in 4 to 6 months with no loss in braking power is a good system.