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Autopapyrus · Chevrolet Aveo (T250, facelift)
https://autopapyrus.com/guides/chevrolet/aveo/brake-master-cylinder-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Chevrolet Aveo (T250, facelift): Brake Master Cylinder Replacement

The master cylinder is mounted on the brake booster in the engine compartment on the driver's side. Replace it if it leaks fluid, if the pedal sinks to the floor, or if the internal seals are worn. The job involves disconnecting two brake lines, replacing the unit, and bleeding the entire system.

Difficulty: Medium Time: 1.5-3 hours including bleeding Steps: 14 Tools: 10 mm and 13 mm wrenches (verify exact sizes on the vehicle), 10 mm flare nut (line) wrench, sockets with ratchet, hose and container for bleeding, syringe or turkey baster for removing fluid, shop rags, DOT 4 brake fluid, drain pan, gloves.

Part

  • 🔩 Master cylinder assembly (ABS and non-ABS versions differ, so compare the number and position of the outlet ports with the old one), reservoir with cap and fluid level sensor, reservoir sealing grommets (if you remove the reservoir separately), DOT 4 brake fluid, about 1 L (1.1 qt)
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Chilton and 4 more. See manuals →

Step by step

14 steps
  1. Park the car on level ground, shut off the engine, apply the parking brake, and turn the ignition off. With the engine off, press the brake pedal several times to release the vacuum in the booster.
  2. Disconnect the negative battery terminal. If the air intake duct or air filter housing is in the way, remove them to access the cylinder.
  3. Remove the fluid from the reservoir with a syringe or turkey baster. Brake fluid damages paint, so lay rags over the fender and the booster.
  4. Disconnect the fluid level sensor connector on the reservoir.
  5. Place a drain pan and rags under the cylinder. Use the flare nut wrench to loosen the flare nuts on the two brake lines and move the lines aside. On ABS versions, the lines run to the hydraulic unit. Do not bend the lines or round off the nut flats: if a nut is seized, treat it with penetrating oil.
  6. Remove the two nuts that secure the cylinder to the booster. Carefully pull the cylinder toward you along the pushrod axis, without tilting it, and remove it. If the reservoir is removable, transfer it to the new cylinder using new sealing grommets.
  7. Compare the new cylinder with the old one: the number of ports, the pushrod length, and the mounting seal. Wipe the booster surface clean.
  8. Install the new cylinder onto the booster studs without tilting it. Tighten the mounting nuts evenly to the manufacturer's specified torque (usually around 15-25 N·m (11-18 lb-ft)).
  9. Thread the line nuts in by hand to avoid cross-threading, then tighten them with the wrench using moderate force, without excessive torque.
  10. Reconnect the level sensor connector. Fill with fresh DOT 4 fluid up to the MAX mark.
  11. Bleed the brakes with a helper, in order from the wheel farthest from the cylinder to the nearest: rear right, rear left, front right, front left. Monitor the reservoir level and do not let it drop to the minimum. Keep bleeding until the fluid comes out free of bubbles.
  12. If the cylinder is dry, bench-bleed it before connecting the lines (on the bench or on the car): with the line nuts loosened, air can be pushed out when the pedal is pressed, then tighten the nuts.
  13. Reconnect the battery. Check that the brake pedal is firm and does not sink when held for 30 seconds, and that the brake warning light on the instrument panel is off.
  14. Inspect the connections for leaks with the pedal pressed. Take a test drive at low speed in a safe area and check braking performance before driving in traffic.

Common mistakes and warnings

  • The brake system is critical to safety. If you have no experience with brakes and bleeding, have the work done at a repair shop. If the pedal is soft, sinks, or has increased travel after replacement, do not drive the car: there is air in the system or a leak. On ABS versions, if the system has been drained deeply, air can get into the hydraulic unit, and bleeding with a scan tool may be required. Do not use fluid that has been sitting in an open container for a long time.
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