The hydraulic vacuum brake booster should be removed in this order.
Remove vacuum from the amplifier system.
Disconnect two hydraulic tubes, vacuum and air rubber hoses from the booster.
Drain the brake fluid from the booster into a vessel.
Remove the amplifier assembly with brackets.
Remove the couplings with bolts and copper piping gaskets.
Disassembly of the hydraulic vacuum booster
The hydraulic vacuum amplifier (Fig. 1) must be disassembled in the following sequence.
Clean the outer surface of the amplifier from dirt.
Install the amplifier in a vise. Install copper gaskets between the vise jaws.
Disconnect the rubber hose from the rear half of the amplifier chamber housing, and then unscrew it, together with the fitting, from the control valve housing.
Make marks on the amplifier camera bodies to ensure their subsequent correct assembly.
Make marks on the hydraulic cylinder and the chamber body adjacent to it.
Remove the two clamps from the amplifier housing.
Hold diaphragm 4 by hand (see Fig. 1), unscrew the pusher nut.
Remove in succession the spring washer of the nut, the small plate 3 of the diaphragm, the diaphragm, the spacer sleeve 5, the large plate 6 of the diaphragm, the spring 9.
Carefully remove the rubber ring together with the pusher washer.
Remove the front housing half, cardboard spacer and sealing rubber ring.
Unscrew the end cap 26 and remove the copper gasket 25.
Unscrew nut 12 of the cylinder seal housing. Remove collar 13 from the seal housing nut.
Remove piston 20 with pusher 18 from the cylinder.
Unpin the piston, remove the cap 24 of the cuff, remove the spring 23 from the piston, remove the ball valve 22 from the piston.
Press the pin out of the piston, remove the piston pusher and the plate pusher 19 of the ball valve.
With light pressure, remove the thrust washer 16 of the piston and the housing 15 of the seals with the rubber ring 14 and the cuff 13 from the cylinder.
Remove the rubber ring from the seal housing and remove the cuff.
Unscrew bypass valves 27 from the booster cylinder.
Remove cover 41 of housing 38 of control valve 31 with gasket 40
Remove the control valve body and remove the control valve from the cylinder.
Remove the spring from the valve body. Remove the valves and their spring.
Using a screwdriver, remove flat shaped washer 34 from the control valve, diaphragm washer 33 and diaphragm 32.
Remove the seal 29 from the lower end of the piston 30 of the control valve.
If the sealing collar of the upper end of the valve piston is in poor condition, press it out.
Remove the piston collar.
Checking and repairing the hydraulic vacuum booster
Wash all metal parts in kerosene, except for the rubber parts and parts of the booster cylinder. Wash these parts in pure alcohol or brake fluid.
Do not allow oil to come into contact with rubber parts. Replace any worn or damaged parts.
The working surfaces of the hydraulic vacuum booster cylinder must be free of scratches, burrs and corrosion.
If these shortcomings are found, it should be honed to a diameter of no more than 22.125 mm for the working surface of the booster piston and no more than 12.58 mm for the working surface of the control valve piston.
In this case, new cuffs should be installed.
If after honing the defect on the cylinder face has not been eliminated, then bore the cylinder and honing it to one of the repair dimensions. In this case, oversized pistons and cuffs must be installed.
Check the threads in the cylinder holes and the cleanliness of the edges for the bleed valves.
There should be no broken threads in the thread, and the edges in the bypass holes should be clear and even around the entire circumference.
The piston of the cylinder of the hydraulic vacuum booster must be free of corrosion and scuffing. In case of one-sided wear, scoring, corrosion or loose fit of the ball (valve), replace the piston.
Piston tappet must have a smooth surface free of burrs and rust. If these shortcomings are found, replace the pusher.
Intensifier chamber diaphragm and control valve in case of detection times To replace cracks, crushing cracks in the sealing ring edges and other damage.
Amplifier chamber spring must be compressed to a height of 120 mm under a load of 9 - 12 kg.
The cuffs of the cylinder piston and the piston of the control valve must be elastic, with sharp sealing edges.
Sealing rubber rings should not have deformation, cracks, breaks.
The piston valve (ball) with a diameter of 6.35 ± 0.025 mm should not have faceting and plaque on the surface and should sit tightly in the booster piston seat.
The control valve piston must be free of nicks, corrosion, and must be securely held in the control valve. If these shortcomings are found, replace the piston.
The control valve must ensure that the piston is firmly pressed into it and that the diaphragm spring washer is securely held. In the absence of this or the presence of nicks on the surface of the seat, replace the valve.
The control valve spring must be compressed with a force of 2.5 ± 0.5 kg to a height of 17 mm.
The control valve body must have a smooth annular groove for a reliable seal of the valve diaphragm and an undented air valve seat.
Atmospheric valve and vacuum valve must have a smooth rubber surface without scratches and roughness for a tight fit of the valves to the seats.
The atmospheric valve spring under a load of 0.3 - 0.05 kg should be compressed to a height of 20 mm.
The spring washer of the diaphragm of the control valve must be flat, with sharp edges along the perimeter of the ledges of the inner diameter, a non-flatness of the washer of 0.2 mm under a load of 1 kg is allowed.
Hydrovacuum booster assembly
Rinse the parts before assembling. Immerse the cuffs in brake fluid with a temperature of at least + 15 ° C.
Lubricate the inside of the cylinder with castor oil or brake fluid.
Assemble the hydraulic booster in the reverse order of disassembly.
When assembling, do not push the piston into the booster cylinder more than 100 mm from the edge of the cylinder, so as not to damage the piston collar.
When assembling the front camera housing with the cylinder, ensure that the holes in the housing, gasket and cylinder are aligned.
Do not put washers under the nuts, the bolts of which are used to fasten the amplifier.
The control valve assembly is shown in fig. 2 and 3.
Installation and testing of a hydraulic vacuum booster
Install the amplifier in the reverse order of its removal.
Couplings are attached with new copper gaskets.
After installing the booster, bleed the brake system.
After assembling and installing the amplifier on the car, check (test) its operation. Tests should determine:
- the tightness of the booster cylinder, the reliability of the sealing collars of the piston pusher, the seals of the control valve and the reliability of all threaded connections of the hydraulic vacuum booster cylinder.
To do this, press the brake pedal with maximum effort, in the absence of vacuum in the system and holding the pedal for 2-3 minutes, make sure that there is no fluid leakage from the system.
After assembly, the cylinder of the hydraulic vacuum booster (before assembling it with the chamber body) must be checked for tightness under a pressure of 90 kg/cm2.
Brake fluid must be supplied to port 1 (fig. 4). At the same time, there should be no leakage of liquid from any point of the cylinder for 1.5 minutes.
Check if there is a decrease in the fluid level in the reservoir of the main brake cylinder;
- tightness of the cuff and valve (ball) of the piston of the booster cylinder.
To determine the tightness of the cuff and piston valve, press the brake pedal with a force of 30 - 40 kg in the absence of vacuum in the system.
Then start the engine, while the pedal will approach the cab floor a little.
Holding the pedal with the same force (30-40 kg) for 2--3 minutes and without stopping the engine, make sure that it does not move;
- - disinhibition of the entire braking system. To do this, raise one of the front wheels of the car or the rear axle and, with the engine running, press the pedal, and then release it. The wheel must turn freely;
- - the tightness of the vacuum chamber, the booster control valve and the entire vacuum pipeline system. To do this, start the engine and, after letting it run a little, turn it off.
After 2-3 minutes, press the brake pedal.
When the vacuum piping, shut-off valve, booster chamber, and control valve are leak-tight, air should be heard hissing, flowing into the amplifier through the air filter, which is located in the driver's cab.