On GAZ-53A and GAZ-66 vehicles, drum-type brakes with a hydraulic drive and a hydraulic vacuum booster are installed
The brakes of the front and rear wheels of the GAZ-53A are the same in design and differ only in size.
The GAZ-b6 rear brakes, unlike the GAZ-53A brakes, do not have protective screens on the brake cylinders, but have rear pads with long linings.
The GAZ-66 front brakes have two cylinders, each of which acts on its own pad.
The design of the brakes is shown in fig. 1 and 2. the action of the hydraulic vacuum booster is based on the use of vacuum in the intake pipe of the engine.
The booster consists of a vacuum chamber, a hydraulically actuated vacuum control valve and a hydraulic cylinder.
All these parts are combined into one hermetically sealed unit, which is mounted on two brackets on the longitudinal beam of the frame.
The vacuum chamber of the booster is connected to the engine suction line through a pipeline and a plate shut-off valve.
A check valve is installed in close proximity to the vacuum source, which maintains maximum vacuum in the amplifier system.
Adjust the clearance between pads and drums. Adjust the brakes when the brake drums are cool and the wheel bearings are properly adjusted.
There are two brake adjustments: current and total
Current adjustment. As the friction linings of the brakes wear, the gaps between the linings and the brake drums increase, and the pedal begins to approach the cab floor when braking.
The current adjustment of the brakes restores the original gaps between the friction linings of the pads and the brake drums, compensating for the wear of the linings.
To adjust the brakes you need:
- - hang the wheel with a jack;
- - rotating the wheel forward, slightly turn the eccentric of the block in the direction of the arrows shown in fig. 1 and 2 until the block brakes the wheel;
- - gradually lower the eccentric, turning the wheel by hand in the same direction until the wheel rotates freely;
- - install the second block in the same way as the first one, while rotating the wheel forward for the front brake of the GAZ-66 car and backward for the rear brake of the GAZ-66 car and all the brakes of the GAZ-53A car.
After adjusting the pad clearance, check the operation of the brakes on the road.
Full adjustment. Wheel brakes should be fully adjusted when changing friction linings, pads or after machining the drums.
When fully adjusting the brakes, you must:
- - hang the wheel with a jack;
- - slightly unscrew the nuts of the support pins and set the support pins of the pads to the initial position;
- - while pressing the brake pedal with a constant force of 12-16 kg, turn the support fingers in the direction indicated by the arrows so that the lower part of the lining rests against the brake drum.
The point at which this happens is determined by the increase in resistance as the support pin rotates. Tighten the support pin nuts in this position;
- - turn the adjusting eccentrics so that the pads rest against the brake drum;
- - release the brake pedal;
- - turn the adjusting eccentrics in the opposite direction so that the wheel rotates freely;
- - thus adjust the brakes of all wheels.
After adjusting the clearance of all brake pads, check the operation of the brakes on the road.
With correctly adjusted clearances between the linings of the pads and the drums, the brake pedal should not drop more than ⅔ of the full travel during full braking.
If, after adjustment, when the car is moving, the brake drums heat up slightly (the hand freely endures when touching the rim of the drum), then after several braking the pads will run in and the heating will stop.
When the drums are very hot, you need to find the pads touching the drums and slightly move them away from the drums with adjusting eccentrics.
Adjusting the clearance between the tappet and the master cylinder piston
The gap between the pusher and the piston of the main cylinder is necessary to prevent spontaneous braking of the car.
If the edge of the sealing collar overlaps the compensation hole 23 (Fig. 3), then the brakes will not be completely released, since part of the liquid cannot flow from the working part of the cylinder into the reservoir after the end of braking.
The clearance should be 1.5-2.5 mm, which corresponds to 8-13 mm of pedal free play, measured in the middle of the footplate.
To measure the gap, you need to change the length of the pusher.
The procedure for adjusting the clearance on a GAZ-53A car is as follows:
- Disconnect the pedal and pushrod, unpin and remove the pin.
- Check the position of the pedal under the action of the release spring.
- The pedal must rest against a rubber buffer fixed under the sloping cab floor.
- Screw (or unscrew) the pedal rod into the piston pusher so that the axis, when rolling in the piston of the main cylinder, is shifted back and does not reach the axis of the pedal hole by 1.5-2.5 mm. Without violating this position, securely lock the pedal connecting rod with a lock nut.
- Align the hole of the connecting rod and the pedal, insert the pin and cotter it. Check pedal free play.
The procedure for adjusting the gap on a GAZ-66 car is as follows:
- Disconnect the intermediate lever and pushrod by removing the eccentric axle.
- Check the position taken by the pedal under the action of the release spring. The pedal should rest against the bracket shelf with a rubber buffer.
- Install the master cylinder piston pusher against the piston at its rearmost position.
- Connect the intermediate lever and the master cylinder piston pusher with an eccentric axis without changing their relative position.
- Turn the eccentric axle in any direction by such an angle as to provide a gap between the pusher and the piston equal to 1.5-2.5 mm.
- Install the washer and tighten the eccentric axle nut.
- Check the amount of pedal free play (8-13 mm) of the brake.
Brake problems and how to fix them
Causes of failure (Remedy)
Brake pedal touches cab floor:
- Increased clearances between brake drums and friction pads
Adjust the brakes using the adjusting eccentrics
If the friction linings are badly worn (0.5 mm left to the rivet heads), then replace them with new ones and perform a full adjustment of the brakes
- Incorrect installation of brake pads
Perform full brake adjustment
- Presence of air in the system
Bleed the system
- Liquid leakage in the piping system
Inspect the entire brake system and locate leaks
If the leakage does not stop after tightening the joints, replace the defective parts with new ones
- Liquid leakage from wheel cylinders or sealing cuffs of the hydrovacuum booster rod
Replace damaged seals, repair damage to cylinders or rod
- Insufficient fluid level in the master cylinder
Add the required amount of liquid
- Fluid leakage through the inner cuff of the master cylinder
Replace the inner cuff with a new one
Brakes do not release:
- Lack of clearance between the pusher and the master cylinder piston
Adjust pedal freeplay
- Clogging of the compensation hole of the brake master cylinder
Clean the expansion hole with soft wire Ø 0.6 mm,
replace the brake fluid if it becomes contaminated by flushing the entire system with alcohol
- Swelling of rubber cuffs due to ingress of mineral oil or some other petroleum-derived liquid into the system
Drain brake fluid, disassemble all cylinders, wash their parts in alcohol
Flush the brake system
Replace brake pads
Before assembling, lubricate the cylinder parts with brake fluid
- Jamming of the piston of the hydraulic vacuum brake booster cylinder
Flush the system with alcohol and replace the fluid.
If the defect persists, remove the amplifier, check the condition of the working surfaces of the cylinder, piston and, if necessary, replace the damaged parts
- Jamming of the piston of the control valve of the hydrovacuum brake booster when returning to the lower position after stopping pressing the pedal
Remove the control valve, wash its piston and cuffs, as well as the hole in the cylinder with alcohol
Replace damaged seals or spring if it is under compression up to a height of 17 mm does not provide a load of 2.5 + 0.5 kg
One brake does not release:
- Weakened or broken brake shoe return spring
Replace the spring if it, when stretched to a length of 227 mm, does not provide a load of 34-39 kg.
- The block is tight on the support pin or stuck in the guide bracket
Identify the cause of seizing and lubricate the sliding surfaces of the parts so that the lubricant does not get on the friction linings
- Seizure of the piston in the wheel cylinder due to corrosion or clogging
Disassemble the cylinder, wash the parts with alcohol.
If necessary, clean the surface of the cylinder with fine-grained sandpaper No. 100.
Before assembling, lubricate the parts with brake fluid
When braking, the car pulls to the side:
- Oiling the friction linings of one of the brakes or two brakes on one of the sides
Wash the linings with gasoline and sandpaper
- - The fastening of one of the brake shields or two shields on one of the sides has loosened
- - Different pressure in the tires of the left and right wheels
Tighten the bolts of the shield(s) and adjust the gaps between the pads and drums, bring the tire pressure to normal
High effort on the pedals due to a malfunction of the hydraulic booster or its system:
- Leaks in vacuum pipeline connections
Fix leaks in pipe connections
- Amplifier air filter clogged
Wash the filter in gasoline, moisten with oil and replace
- Amplifier camera diaphragm torn
Disassemble the amplifier chamber and replace the diaphragm