System Maintenance and Failures Analysis
Brake caliper is locking
The so called ―locking‖ failure refers to brake caliper does not return to the original position, that is one
of the common failures of brake system. There are many reasons causing such kind failures, such as brake
caliper is blocked, booster pump is blocked or brake caliper valve is blocked. If the brake caliper of front and
rear bridge is locking, it is may caused by blocking of pneumatic brake caliper. When the failures are solved,
loosen pipeline between booster pump and brake caliper, manually chek if the brake caliper can return, if it
does not work, it may be caused by blocking of brake caliper, if it can be returned manually, but booster
pump may be blocked.
No brake or brake distance is too long
1. Pressure adjustment is improper, which causes pressure of compressed air is too low, brake moment is
too small. Adjust pressure gauge to the regulated range.
2. It may be caused because air compressor is air leaking or air inlet and outlet valve are blocked because
wearing of cylinder barrel and piston ring is too much, driving belt is too loosened. The worn parts shall
be replaced in time.
3. Foot brake valve is adjusted improperly, when brake pedal is stepped to the end, air inlet valve of brake
valve is not totally opened, air throttle is caused, air pressure becomes weak when going through foot
brake valve, and it cannot reach rated working pressure. Adjust the adjusting screw of brake pedal.
4. Failure of booster pump: sealing ring of booster pump is worn, compressed air goes into low pressure
chamber, and movement of brake pump piston is slow, or even there is no moving distance, which
cause braking power is not enough; compensation hole of brake pump is blocked by dirt, brake fluid
cannot go into ante chamber of piston and oil in brake oilway is not enough.
Brake lags behind
1. Air in brake system is not evacuated, air is compressed when braking, air resets when releasing brake,
which affects returning of friction plate.
2. Brake air pressure is not enough;
3. Piston of brake caliper is blocked;
4. Foot brake air bleeder or filter screen is blocked, return spring of valve core is broken, piston cannot
return and blocks outlet of air hole, which makes brake air discharging is not smooth, brake pressure
and oil pressure cannot reduce quickly, brake moment cannot be released, thus it is laged behind.
5. The hole of non-pressure chamber of booster pump connecting with air is blocked or return spring is
broken, which affects sensitivity of chamber piston return and cause lag.
Braking deviation
The direct reason of braking deviation is the brake moments of the left side and right side wheels are
different, the common phenomenons are:
1. Brake caliper of one side of the wheel is locking, it is hard to trip off during travelling, and usually the
rectangle sealing ring of brake caliper is broken.
2. When stepping foot pedal, one side brake caliper is braking, while the other side is inside leaking and
oilway is blocked, brake fluid cannot go into brake caliper, which makes different brake moments and
causes deviation. Under such kind of condition, please check if the sealing rings of gas cap and brake
caliper are turned up or the pipelines are blocked.
There is birdle during braking, and brake is hot
1. Connection screws between brake caliper and drive axle are loosed, they rub, impact or abrade each
other.
2. There are hard things between brake lining and brake disc.
Brake System SPC000021
Page 9
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