Replacing Brakes

Measuring Rotors & Brakes

Simply remove the bottom sliding pin on the calliper, The calliper will then move up just like the pic above. Once the  calliper is out of the way then the brake pads should slide out, sometimes they might need a tap.

The calliper - Is what the brake line runs to, to the front brakes & pumps the fluid behind the the piston.
The piston is what pushes against the inside pad.
The calliper moves on sliding pins &  pulls against the outside pad.

The sliding pin helps the calliper move, It will most all ways be the bottom sliding pin that is removed to get the pads off.

Once the sliding pin has been removed then the calliper will slide up.
Remember if the pads need replacing the piston will need to pushed back. A G-clamp can do this with a piece of small timber.

When the calliper might need a bit of a nudge to get out.

Once everything has been removed & we can see the rotors, then we can start our visual inspection.

The pads removed!
With the shims.

The three pics below are showing how to measure the thickness of the pads using an Vernier Calliper

When checking the pads we need to check for even wear, Check the shims for cracks or even rust.

These rotors are vented rotors which means the holes/vents on the side are there to help cool down the rotors when there is braking applied & begin to get hot.

When measuring the rotors we are using a Micro Meter to check the thickness of the rotor.
We are also looking for Cracks, rust & deep scratches. If the rotor is within specs then we can make a decision if it needs to be machined or replaced.

The pic on the left  is showing the back right drum & disk. Not every vehicle will have these, Some will just have a drum. When servicing the back brakes we needed to remove the calliper completely.
How this one works is when the piston winds on to the back brake pad. 

The pic on the right is showing the back drum & disk
Another thing to measure is the run out of the rotor, by doing this we use the DTI Gauge. Unfortunately I didn't get any photos of this.

Master Cylinder & Bleeding Brakes

Master Cylinder & Bleeding Brakes

The master cylinder:

This is where the pressure is created & converted from non - hydraulic pressure to hydraulic pressure. Brake fluid is held in the reservoir, when the brake pedal is applied it pushes against the push rod which then pushes the piston. At the end of the piston is a L-type seal which helps keep the pressure & stops the fluid getting past into the non - pressure side of the cylinder.

Brake Bleeding

When bleeding brakes a small hose is usually connected to the bleeder nipple & using an 8mm spanner to open the nipple. Pump the brakes till pressure starts to build up, then hold the pedal, Open the nipple & the pressure will release by pushing on the pedal. This will push out any old fluid & all so get rid of any air bubbles if there are any.

Further down this blog is more ways to bleed brakes.

The master cylinder contains:
2x Pistons - Primary piston is at the front, Secondary piston is at the back.
1x Reservoir - which holds the fluid
1x master cylinder body
3x L-type seal
1x O ring
1x Circlip - This helps hold in all of the above

Pressure Testing The Master Cylinder:
When pressure testing the master cylinder first we must block off the primary & secondary circuit with a couple of bolts.

Fill the reservoir up fluid, then slightly loosen the bolts. Then proceed to push on the primary piston with something solid, this will push out all the air bubbles, then tighten the bolts back up.
Then we push back on the primary piston, if there is no pressure build up on the pistons & pressure is being lost then we there is a problem/ leak somewhere inside.

The video below is showing how this is all done!

There are many ways you can drain the fluid from the reservoir.
1. Gravity fed - This is where a small hose is attached to the bleeder nipple. The bleeder nipple is then opened & the fluid slowly drips in to a container.
2. Attach small hose to bleeder nipple & pump the fluid out by pumping the brakes.
3.Attach a Vacuum Brake Bleeder to the bleeder nipple, open nipple. Vacuum Brake Bleeder will then suck the fluid out.
The video below will show how we got the fluid out of the reservoir.

Gravity Drip

Brake Vacuum Bleeder

To the left is the vacuum bleeder.
This is hooked up to a air compressor & the white hose is connected to the brake bleeder nipple.

When the vacuum bleeder is connected the we connect the reservoir filler, after it has been filled with brake fluid.

The vacuum is then switched on & the old fluid is sucked out & replaced with new fluid straight away.

The video below shows the  vacuum brake bleeder working!

Brake Roller Testing

Brake Roller Testing

Brake roller testing is not only to test how well the vehicle brakes work or if they work at all, But to check the vehicles shocks & suspension.

The video on the left is demonstrating how the shock test is done.

The vehicle is driven on to the red device which is able send small & large amounts of vibrations up through to the shocks.

This information is then sent to a computer running the right system, to tell us how well the vehicle shocks are working.

To the right is the results of the shock test above,
Over all results of the test for the front axle was:
Left - 60% at 24mm, Right - 58% at 25mm with an imbalance of 2% 
> 40% Normal
< 40% Effect weak
< 20% defect

Next was the front braking test on the brake rollers.
Once front wheels are on the rollers, The vehicle is then put in neutral & the rollers move the front wheels.

Front Left - 4.44kN

Front Right - 4.62kN

Imbalance - 4%

The video on the right is of the front brake roller testing. The front brakes are then slowly applied as the rollers are moving. Eventually fully applying them.

The video on the right is of the above brake roller tester.It will show when the brakes are applied & when the brakes are held & then fully applied.

Brakes applied - the blue level rises

Brakes held - the blue level sits within the yellow zone.

Brakes Fully Applied - the yellow level to the right counts down to the left, Once it has completely counted down then the brakes are full applied.

Next is the back shock absorbers to be tested.
The same process is applied to the back as it was to the front.

The over all result of the Rear Shocks:

Left - 58% at 36mm, Right - 54% at 39mm with an imbalance of 4%


> 40% Normal
< 40% Effect weak
< 20% defect

Video on the right is of the bake shock absorbers.At the bottom of the screen you will see a wave start to form this is from the first shock, The second wave that will appear will be reading of the second shock.

Next we test the Rear Brakes & the Parking Brake/ Hand Brake.
Them same as the Front Brake test is applied with the Rear Brakes.
But with the Rear Brakes we found that when fully applied they didn't completely stop the back wheels from spinning.

To the right is another video showing you the results & how the test is done.

Rear Left - 2.15kN

Rear Right - 2.40kN

Imbalance - 10%

Testing the Parking Brake has the same process as testing the Front & Back Brakes

The video on the right is showing you the test results as the test is being done.

Parking Brake:

Left - 1.23kN

Right - 2.13kN

With an Imbalance of 42%

Once all these test have been done, we then had to take the vehicle out & jack it up on axle stands. Removing all tyres & fix any problems that needed attending to. The following pics below show us working on the Rear Brakes.

Unfortunately even after we thought we had fixed the problems, we still ended up failing the roller test. Due to the hand brake not being tight enough.
This would be an easy problem to fix but unfortunately we had run out of time.

Brakes Off Car, Wheel Cylinder

Wheel Cylinder

Wheel Cylinder:

The wheel cylinder is made up of nine parts, 

1 x Cylinder - (Bottom Right Of Pic), 

2 x Piston's - with 2 x Cup seal's that sit on the inner face of piston's - (Left Hand Side Of Pic),

1 x Spring - This sit's in between the two pistons - (Middle Of Pic),

2 x Dust/ Boot seal's - These sit on the end of the cylinder, These also hold in the piston's - (Top Right Of Pic).

 Dismantling the wheel cylinder 

To remove the end boot, gently use a flat-head by sliding up under the boot. Being careful not to ripe the boot.

Once both boots are off, Next is to tap out the two piston's - once again being careful the spring doesn't go flying out.

The pic on the right is the wheel cylinder fully dismantled & laid out the way it fits together.

Honing out the cylinder

Inspect inside the cylinder for any corrosion or even rust, most likely it will need to be Honed.

To the right is a video on how to hone out the inside of the cylinder.

There are two types of honing bits.

One with two stone's & one with three stone's

Pic on right - Is from our work books.
Showing the two different types of honing tools.

 On the right is of the cylinder after it has been honed.



On the left is what the cylinder looked like before it was honed.







After everything has been replaced that needed to be replaced or in our case it needed to replaced with a new one.