GEDDES AUTOMOTIVE BRAKE MASTER & CALLIPER REPAIRS / REPLACEMENT
MY BRAKE PEDAL FEELS SPONGY. PHONE: 636 7064
Geddes Automotive Auckland service & repair brake calliper & cylinder problems for cars vans & trucks. We fix car hydraulic brakes problems. We supply & fit brake master cylinders, flush & bleed hydraulic brake systems.
HOW DO CAR BRAKES WORK?
There are various designs but basically this is how most van & car hydraulic brakes
When you put pressure on the brake pedal, that pushes the piston in the brake master cylinder,
that in turn forces brake fluid into the brake lines and out to the wheel cylinders (car brake cylinder). If there is a
brake oil leak in the brake system then oil pressure could be lost reducing the braking effect. Air
could also be being sucked into the hydraulic brake system. Air compresses more than brake oil so
reduces the braking effect and gives a spongy brake pedal.
Most vans & car brakes have either a power booster in the brake system, often part
of the brake master cylinders or more modern cars with ABS brakes have an ABS pump which like the
power booster assists the car hydraulic brakes line oil pressure and increases the braking effect.
Drum brakes have wheel cylinders (car brake cylinder) with hydraulic pistons that force the brake linings onto
the drums. Disc brakes have brake callipers, the piston (or pistons of van & car brake callipers) clamp the
brake pads onto the brake rotor (brake disc). Linings and pads when forced against the drum or brake
disc cause friction and slows the wheel from turning.
CLICK ON THE TYPE OF BRAKE REPAIR YOU REQUIRE:
Brake Master Cylinder
Cylinder & linings
SPONGY BRAKE PEDAL
If you have a spongy brake pedal check the brake fluid reservoir to see if the oil level
has sunk. If the level has dropped then the oil must be going somewhere — look for oil leaks usually
behind the wheels, under the brake caliper, under the brake drum, on the inner side of the tyre, under
the carpet behind the brake pedal. If a brake seal is worn out oil can leak out and air can be sucked in.
Some vehicles have a proportion valve. This proportions the brake line pressure so there
is equal pressure on the LH side & RH side of the vehicle. If a brake oil seal is failing this can cause brake
problems such as a spongy brake pedal.
ABS HYDRAULIC BRAKE SYSTEMS
ABS hydraulic brakes is also discussed on page "ABS BRAKE LIGHT STAYS ON RESET".
The ABS control unit is a series of electronically operated valves. These valves should open & close when commanded
by the ABS computer. It is very important that the brake fluid is flushed every 3 years at least. The brake
fluid oil is deliquescent (means it absorbs moisture from the air). The moisture boils at a
lower temperature than brake oil and can cause brake fade. Moisture gets into the ABS valves and brake master & slave
cylinder pistons (car brake cylinder pistons)and causes those to corrode and eventually seize. This reduces brake efficiency and also is
a cause of unbalanced brakes. This can cause your ABS light to come on and to fail your WOF.
BRAKE SYSTEM BLEEDING & BRAKE FLUSHING
On non ABS brake systems, brake bleeding is easier than on ABS brake system. If there is air already in the brake system then it is more difficult to force the air out compared to a straight brake flush.
If the van truck or car brakes have ABS then sometimes we need to command the control
valves to open to allow the brake fluid and air (if air is in the system) to pass through and be expelled
through the brake bleed nipple on the brake caliper or wheel cylinder.
We have 2 types of brake bleeding equipment; vacuum and pressure bleeding.
COST TO FLUSH BRAKES
Straight forward flush from $69.00 + GST
Depending on the type, make, model & year of your vehicle, depends on what parts are
required. Once we have diagnosed the brake problem we can advise the options and costs for your ABS & hydraulic
brake repair fix.