Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

Master Cylinder

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REMOVAL & INSTALLATION



1970-73 140 Series

See Figure 1

  1. To prevent brake fluid from spilling onto and damaging the paint, place a protective cover over the fender apron, and rags beneath the master cylinder.
  2.  

Siphon the fluid out of the reservoir prior to removal to minimize spillage.

  1. Disconnect the brake lines from the master cylinder and plug them immediately.
  2.  
  3. Remove the two nuts which retain the master cylinder and reservoir assembly to the vacuum booster, and lift the assembly forward, being careful not to spill any fluid on the fender. Empty out and discard the brake fluid.
  4.  


CAUTION
Do not depress the brake pedal while the master cylinder is removed.

In order for the master cylinder to function properly when installed to the vacuum booster, the adjusting nut for the thrust rod of the booster must not prevent the primary piston of the master cylinder from returning to its resting position.

  1. A clearance (C) of 0.020-0.059 in. (0.5-1.5mm) is required between the thrust rod and primary piston with the master cylinder installed. The clearance may be adjusted by rotating the adjusting nut for the booster thrust rod in the required direction.
  2.  
  3. To determine what the clearance (C) will be when the master cylinder and booster are connected, first measure the distance (A) between the face of the attaching flange and the center of the primary piston on the master cylinder.
  4.  
  5. Then measure the distance (B) that the thrust rod protrudes from the fixed surface of the booster (making sure that the thrust rod is depressed fully with a partial vacuum existing in the booster).
  6.  
  7. When measurement (B) is subtracted from measurement (A), clearance (C) should be obtained. If not, adjust the length of the thrust rod by turning the adjusting screw to suit.
  8.  



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Fig. Fig. 1: Adjust the brake booster thrust rod as necessary, so that dimension (A) minus (B) = (C)-1970-73 140 series

  1. After the final adjustment is obtained, apply a few drops of locking compound to the adjusting nut.
  2.  
  3. Position the master cylinder and reservoir assembly onto the studs for the booster, and install the washers and nuts. Tighten the nuts to 17 ft. lbs. (23 Nm).
  4.  
  5. Remove the plugs and connect the brake lines.
  6.  
  7. Bleed the entire brake system.
  8.  

1974 140 and 164; All 1800, 200 and 700 Series

See Figures 2 through 7

  1. To prevent brake fluid from spilling onto and damaging the paint, place a protective cover over the fender apron, and rags beneath the master cylinder.
  2.  

Siphon the fluid out of the reservoir prior to removal to minimize spillage.



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Fig. Fig. 2: Exploded view of the master cylinder piston assembly-240, 260 and 1980 and later models



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Fig. Fig. 3: Remove the cap and the debris trap to remove the fluid prior to master cylinder removal



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Fig. Fig. 4: An ordinary turkey baster works well as a mini-siphon to remove the brake fluid

  1. Label and disconnect the brake lines from the master cylinder and plug them immediately. If the vehicle has a hydraulic clutch, disconnect its line from the fluid reservoir. Plug it and secure the line out of the way.
  2.  



Click image to see an enlarged view

Fig. Fig. 5: Remove the lines by detaching the flange fittings-use a catch pan to prevent fluid from spilling onto the engine components below

  1. Remove the two nuts which retain the master cylinder and reservoir assembly to the vacuum booster, and lift the assembly forward, being careful not to spill any fluid on the fender. Empty out and discard the brake fluid.
  2.  



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Fig. Fig. 6: Unbolt the master cylinder from the brake booster as shown



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Fig. Fig. 7: Remove the detached master cylinder from the brake booster


WARNING
Do not depress the brake pedal while the master cylinder is removed!

  1. To install, place a new sealing rim (if equipped) onto the sealing flange of the master cylinder. Position the master cylinder and reservoir assembly onto the booster studs, and install the washer and nuts. Tighten the nuts to 9-11 ft. lbs. (12-15 Nm).
  2.  
  3. Remove the plugs and loosely connect the brake lines. Have a helper depress the brake pedal to remove air from the cylinder. Tighten the nuts for the lines when the brake fluid (free of air bubbles) is forced out. Reconnect the lines for the hydraulic clutch if so equipped.
  4.  
  5. Bleed the entire brake system. If the car has a hydraulic clutch, bleed the clutch system.
  6.  

OVERHAUL



164 and 1800 Series
  1. Remove the master cylinder from the booster.
  2.  
  3. Firmly fasten the flange of the master cylinder in a vise.
  4.  
  5. Position both hands beneath the reservoir and pull it free of its rubber seals. Remove the filler cap and strainer from the reservoir, as well as the rubber seals and nuts (if so equipped) from the cylinder.
  6.  
  7. Remove the stop screw. Using a pair of snapring pliers, remove the snapring from the primary piston and shake out the pistons.
  8.  
  9. Discard both the primary and secondary pistons.
  10.  
  11. Clean all reusable metal parts in clean brake fluid or methylated alcohol. The parts must be thoroughly dried with filtered, water-free compressed air, or air dried. All cleaning alcohol must be removed from the parts, as it lowers the boiling temperature of brake fluid. If the inside of the cylinder is scored or scratched, the cylinder must be replaced. Minor pitting and corrosion may be removed by honing. Remember to flush the cylinder clean after honing, and make sure that the passages are clear. Check the cylinder bore for excessive wear.
  12.  
  13. Make sure that the new rubber seals, a new brass washer and back-up ring are installed on the new secondary piston. Make sure that the rubber seals are pointing in the right direction.
  14.  
  15. Coat the cylinder bore with brake fluid and dip the secondary piston and seals in brake fluid prior to installation. Install the secondary piston and spring in the bore, taking care not to damage the rubber seals.
  16.  
  17. Make sure that the new rubber seals, metal washers, plastic washer, back-up ring, sleeve, and springs are installed on the new primary piston. Make sure that the seals are facing in the right direction.
  18.  
  19. On 1800 models, compress the primary piston spring and tighten the screw for the sleeve until it bottoms. Tighten the screw to 1.5-2.2 ft. lbs. (2-3 Nm).
  20.  
  21. Dip the primary piston assembly in brake fluid and install it in the bore, taking care not to damage the rubber seals. While holding the piston in the bore, install the snapring.
  22.  
  23. Check that the hole for the stop screw is clear, and install the new stop screw and sealing washer. Tighten the screw to 3.5-5.7 ft. lbs. (4.75-7.75 Nm) on all 164 and 1800 series.
  24.  
  25. Check the movement of the pistons and make sure that the flow-through holes are clear. The equalizing hole is checked by inserting a 25 gauge (1800) or 22 gauge (164) soft copper wire through it and making sure that it is not blocked by the secondary piston seal. If it is blocked, the master cylinder will not function properly and must be reassembled.
  26.  
  27. Install the nuts (if so equipped), new rubber seals and washers onto the master cylinder at the reservoir connections. After making sure that the venting hole in the cap is open, install the cleaned strainer and cap. Press the reservoir into the master cylinder by hand.
  28.  
  29. Install the master cylinder.
  30.  

140, 200 and 700 Series-Non-ABS System

See Figures 8 through 12

  1. Remove the master cylinder from the booster as outlined in this section.
  2.  
  3. Firmly fasten the flange of the master cylinder in a vise.
  4.  



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Fig. Fig. 8: Cross-sectional view of the type 2 secondary piston-140 series



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Fig. Fig. 9: Place the master cylinder firmly in a vise



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Fig. Fig. 10: Using a pair of snapring pliers, remove the snapring from the primary piston

  1. Position both hands beneath the reservoir and pull it free of its rubber seals. Remove the filler cap and strainer from the reservoir, as well as the rubber seals and nuts (if so equipped) from the cylinder.
  2.  



Click image to see an enlarged view

Fig. Fig. 11: Pull out the primary pistion assembly and shake off any excess brake fluid into a drain pan-do not allow the fluid to contact painted surfaces

  1. Remove the stop screw. Using a pair of snapring pliers, remove the snapring from the primary piston and shake out the piston.
  2.  



Click image to see an enlarged view

Fig. Fig. 12: The master cylinder disassembled-ONLY allow fresh brake fluid to contact the components. NO other cleaners or solvents are acceptable

  1. Remove both the seal from the secondary piston, taking care not to damage or score the surfaces of the plunger. The old primary piston should be discarded and replaced.
  2.  
  3. Clean all reusable metal parts in clean brake fluid or methylated alcohol. The parts may be allowed to thoroughly air dry, or compressed air may be used. All alcohol must be removed from the parts, as alcohol lowers the boiling temperature of brake fluid. If the outside of the cylinder is scored or scratched, the cylinder must be replaced. Minor pitting or corrosion may be removed by honing. Remember to flush the cylinder clean after honing, and make sure that the passages are clear. Check the piston for damage and proper clearance in the bore.
  4.  
  5. Install new seals on the secondary piston, making sure that they are positioned in the proper direction.
  6.  
  7. Coat the cylinder bore with brake fluid and dip the secondary piston and seals in brake fluid prior to installation. Slide the spring, spring plate, and washer onto the secondary piston and install the assembly in the bore, taking care not to damage the seals. Dip the new primary piston and seal assembly in brake fluid. Press the primary piston assembly into the bore and install a new washer and snapring.
  8.  
  9. Make sure that the hole for the stop screw is clear and install the new top screw and sealing washer.
  10.  
  11. Check the movement of the pistons and make sure that the flow-through holes are clear. The equalizing hole (140 series only) is checked by inserting a 25 gauge soft copper wire through it and making sure that it is not blocked by the secondary piston seal. If it is blocked, then the master cylinder in incorrectly assembled, and you must take it through the numbers again.
  12.  
  13. Install the nuts (if so equipped), new rubber seals, and washers onto the master cylinder at the reservoir connections. After making sure that the venting hole in the cap is open, install the cleaned strainer and cap. Press the reservoir into the master cylinder by hand.
  14.  
  15. Install the master cylinder.
  16.  

ABS System
  1. Remove the master cylinder as described previously. Drain and remove the fluid reservoir. Remove the two seals between the reservoir and the cylinder.
  2.  
  3. Remove the washer in the front hole of the cylinder.
  4.  
  5. To disassemble the master cylinder, press the pistons into the cylinder while using a pair of long-nosed pliers to remove the locking pin through the front hole.
  6.  
  7. After the lock pin is removed, remove the lock ring for the pistons and remove the pistons.
  8.  
  9. Clean all reusable metal parts in methylated alcohol. The parts may be allowed to thoroughly air dry, or compressed air may be used. All alcohol must be removed from the parts, as alcohol lowers the boiling temperature of brake fluid. If the bore of the cylinder is scored or scratched, the cylinder must be replaced. Minor pitting or corrosion may be removed by honing. Remember to flush the cylinder clean after honing, and make sure that the passages are clear. Check the piston for damage and proper clearance in the bore.
  10.  
  11. Install the pistons into the cylinder. Turn the oval opening of the front stage so that it faces the fluid reservoir hole.
  12.  
  13. Press the pistons in to the bottom of the cylinder and install the lock pin through the front hole. Release the pistons and check that the lock pin holds the front stage.
  14.  
  15. Press the pistons inward again and install the lock ring.
  16.  
  17. Install the washer in the front hole and reinstall the two sealing rings. Use new rings if any damage is seen.
  18.  
  19. Install the master cylinder.
  20.  
  21. Bleed the brakes.
  22.  

 
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