1. With the unit removed from the machine, clean off any external dirt and remove the reservoir (Section 15, paragraph 7).
2. Insert the rod into the end of the cylinder and press the piston until it can be held in this state by inserting a smooth pin or rod with a diameter of 3.0 mm (0.118 inch) into the primary hole.
3. Pull the snap ring out of the end of the cylinder using pliers or screwdrivers. Throw away the circlip (Pic. 9.37).
Pic. 9.37 — Removing the master cylinder spring ring (GMF)
4. Remove the primary piston by first removing the temporary retaining pin. Pay attention to how the seals are installed.
5. Remove the secondary piston by tapping the end of the cylinder against a piece of wood. Pay attention to how the seals are installed.
6. Disassemble the primary piston. This can be done by compressing the spring with an aerosol cap or something similar that has a hole drilled into it. Once the snap ring is exposed, remove it with two screwdrivers and discard it.
7. Inspect the surfaces of the pistons and cylinder barrel for scratches or metal-to-metal friction. If this is the case, replace the entire master cylinder.
8. If the components are in good condition, clean them in hydraulic fluid or methyl alcohol - and nothing else.
9. Obtain a repair kit that contains all the necessary spare parts.
Procedures for working with the kit "free" oil seals.
10. Install the seals on the pistons, pushing them into place only with your fingers. It is important that the new seals are installed in the same way as the old ones; They are cone-shaped and will only function correctly if installed in the correct order.
11. Reassemble the primary piston using a new snap ring. The spring ring can be inserted into its groove all the way by tapping it with a piece of pipe.
12. Dip the pistons into clean hydraulic fluid and install the secondary piston into the cylinder, followed by the primary.
13. Push and hold the primary piston as directed for disassembly while you install the new snap ring.
14. Install new rubber sealing rings and install the fluid reservoir in its place on the cylinder body.
15. Pour some clean fluid into the reservoir and prepare the master cylinder for operation before installation by pressing the primary piston several times with a rod. Naturally, a large amount of liquid will be ejected from the open ports of the cylinder.
Procedures for working with a pre-assembled kit.
16. Lubricate the cylinder barrel with brake fluid or brake rubber grease. Clamp the cylinder so that the barrel is in a horizontal position.
17. Remove the plug from the tube and insert the short part of the tube into the cylinder barrel up to the collar on the tube. Using a blunt rod, push the piston out of the tube and into the barrel; hold the pistons in the barrel using the smooth rod or needle used during disassembly. Remove the rod and tube.
18. Install a new spring ring on the end of the cylinder. Press down on the primary piston and remove the retaining rod or needle. Make sure the circlip is in place and that the pistons can move freely.
19. Install new seal rings and reinstall the reservoir.
20. Prepare the cylinder for operation as indicated for the ATE type cylinder in the previous Section (paragraph 25).
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Pic. 9.36 — GMF type master cylinder disassembled 1. Body. 2. Tank seal rings. 3. Spring rings. 4. Reservoir. 5. Cap with warning switch. 7. Spring. 8. Spring retaining device. 9. Secondary piston seals. 10. Washer. 11.Secondary piston, 12.Primary seals. 13. Spring ring. 14. Spring cuff. 15. Primary piston spring. 16. Spring retaining device. 17. Primary piston. 18. Spring ring.
Pic. 9.38 — Removing the spring ring of the primary piston of the main cylinder (GMF)
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