Cost of break pad + caliper for Astra 2008 model

Gloomendoom wrote: »

I must admit that I replace callipers and wheel cylinders in pairs. My reasoning is that if one has failed, the other one can't be far behind.

By that reasoning, would you suggest that the OP should have replaced all four calipers?

sevenhills wrote: »

By that reasoning, would you suggest that the OP should have replaced all four calipers?

Now you are being silly, only one set needs to be replaced, to keep balance across a axle.
All four wheels should be bleed, until clean fluid come though, What I do is vacuum the reservoir (not with a hover) fill with a clean unopened bottle and suck or push the fluid round the system until clean fluid come out into the bottle.

onomatopoeia99 wrote: »

Brake calipers are simple hydraulic devices. Unless something is seriously wrong with them, their performance doesn't degrade with time / use.

OK lets look at this statement, And I'll use this Astra's rear Calipers as an example ,

There is 3 moving parts, the piston, the slider's and handbrake gear.

These sliding calipers are prone to seizure due to corrosion in two areas.

if the slider's are seized, then no need to replace the whole caliper, you can remove the old ones, clean, grease and replace the slider's.

The rear Calipers on this car have the hand brake incorporated into the caliper.

This works by using a gear inside the piston,

Brake fluid has hygroscopic properties - meaning that it absorbs moisture during its life in your car through the pipes, hoses and joints that it lubricates, (See more about brake fluid blow)

The moisture corrodes the Piston, bores and handbrake gears of the caliper and hardens the seals, resulting in the caliper seizing ( this is why is so important to do a brake fluid change at least every 2 years)

Their performance degrade with time / use

Why is brake fluid important?
Brake fluid plays a crucial role in your braking system as it transfers the force created when a driver presses the brake pedal directly onto the wheel hub.

Heat generated under braking, especially under heavier breaking or prolonged breaking, may affect the brake fluid which can only work if it is liquid and not so hot that it has become vapour.
Therefore the boiling point that your brake fluid can achieve is critical to efficient braking as temperatures above the boiling point form vapour bubbles in the system, potentially resulting in brake failure.
In addition, the brake fluid serves as a lubricant of all movable parts and prevents corrosion. It has to be compatible with rubber seals and hoses thus allowing braking systems to achieve long service and optimal performance.
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Why does brake fluid deteriorate?
Brake fluid has hygroscopic properties - meaning that it absorbs moisture during its life in your car through the pipes, hoses and joints that it lubricates.

As the water content in the brake fluid increases, the temperature the liquid boils at decreases. The boiling point can be significantly reduced by water contamination which will have a negative effect on your braking ability.

Whilst regular servicing of your vehicle will include checking the boiling point of your brake fluid, vehicle manufacturers recommend that you change your brake fluid at least every two years if not sooner (check your vehicle handbook for details).

Changing brake fluid when recommended prevents brake failure and maintains the boiling point at a safe level.