Brake Fluid Replacement and Bleeding Brakes – 2.5L NA

Overview

This procedure replaces old brake fluid and bleeds the brake system to remove air and moisture, ensuring optimal braking performance for your Porsche 944 (8-valve engine configuration). Brake fluid absorbs moisture over time, which can cause steam voids during hard braking, reducing braking capability, or lead to internal corrosion of brake components. Regular replacement—annually or more frequently for track use—is critical to maintain safety and performance. Use only DOT 4 brake fluid, such as ATE Super Blue for track-driven cars, and never use DOT 3 or DOT 5.

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Tools Required

• Jack stands or ramps
• Container to catch brake fluid
• Turkey baster or hand vacuum pump brake bleeder (vacuum pump required for one-person bleeding)
• Wrench (size varies by bleeder screw, typically 8mm (5/16 inch) or 10mm (3/8 inch))
• Clean rags

Parts Required

• DOT 4 brake fluid, 1 liter (1 quart), such as ATE Super Blue

Step-by-Step Procedure

Step 1: Prepare the Vehicle and Reservoir

1. Park the vehicle on a level surface and place it on jack stands or ramps to ensure safe access to all four wheels.
2. Locate the brake fluid reservoir under the hood, near the driver’s side firewall, and remove the reservoir cap.
3. Use a turkey baster or hand vacuum pump brake bleeder to remove as much old brake fluid as possible from the reservoir. Dispose of the old fluid properly at a recycling center.
4. Wipe the inside of the reservoir with clean rags to remove any debris, ensuring no dirt or contaminants enter the system.
5. Refill the reservoir with fresh DOT 4 brake fluid, such as ATE Super Blue, to the “MAX” mark.

Step 2: Bleed the Brakes (Two-Person Method)

6. Start with the right rear caliper (farthest from the master cylinder), then proceed to the left rear, right front, and left front.
7. Place a catch pan and clean rags under the caliper to catch spilled fluid. Identify the bleeder screw and select the correct wrench size (typically 8mm (5/16 inch) or 10mm (3/8 inch)). Remove the rubber boot from the bleeder screw.
8. Have a second person sit in the driver’s seat. Instruct them to pump the brake pedal several times (3–5 pumps) and then hold it firmly in the depressed position.
9. While the pedal is held down, open the bleeder screw by turning it counterclockwise (about 1/4 to 1/2 turn). Catch the fluid in the container. The brake pedal will sink to the floor—this is normal. Do not let the person release the pedal until the bleeder is closed.
10. Close the bleeder screw by turning it clockwise until snug, but do not overtighten (torque to approximately 7 Nm (5 ft-lbs)). Instruct the person to release the brake pedal.
11. Repeat the pumping, holding, and bleeding process until clean, bubble-free brake fluid flows from the bleeder screw.
12. Wipe up any spilled brake fluid immediately with clean rags, as it can damage paint and components.
13. Check the reservoir and refill with DOT 4 brake fluid to the “MAX” mark as needed to prevent air from entering the system.
14. Repeat steps 6–13 for the left rear, right front, and left front calipers in that order.

Step 3: Bleed the Brakes (One-Person Method with Vacuum Pump)

15. If working alone, use a hand vacuum pump brake bleeder. Start with the right rear caliper, then proceed to the left rear, right front, and left front.
16. Place a catch pan and clean rags under the caliper. Select the correct wrench size (typically 8mm (5/16 inch) or 10mm (3/8 inch)) and remove the rubber boot from the bleeder screw.
17. Attach the vacuum pump to the bleeder screw using an adapter that ensures a tight seal.
18. Pump the vacuum pump approximately 10 times to create suction, then open the bleeder screw by turning it counterclockwise (about 1/4 to 1/2 turn).
19. Continue pumping the vacuum pump as fluid flows into the container until clean, bubble-free brake fluid appears.
20. If the vacuum pump container fills before clean fluid is achieved, close the bleeder screw, empty the container, and resume bleeding.
21. Close the bleeder screw by turning it clockwise until snug (torque to approximately 7 Nm (5 ft-lbs)).
22. Wipe up any spilled brake fluid immediately with clean rags.
23. Check the reservoir and refill with DOT 4 brake fluid to the “MAX” mark as needed.
24. Repeat steps 15–23 for the left rear, right front, and left front calipers in that order.

Step 4: Bleed the Clutch (If Applicable)

25. If your Porsche 944 has a hydraulic clutch (standard on 2.5L NA models), bleed the clutch slave cylinder, located near the transmission on the driver’s side.
26. Follow the same bleeding process as for the brakes, using either the two-person method (steps 6–13) or the one-person vacuum pump method (steps 15–23), depending on your setup.
27. Ensure clean, bubble-free fluid flows from the clutch slave cylinder bleeder screw.

Post Procedure Checklist

• Verify that the brake fluid reservoir is filled to the “MAX” mark with DOT 4 brake fluid.
• Check all bleeder screws for tightness and ensure rubber boots are reinstalled.
• Inspect for leaks at all calipers and the clutch slave cylinder (if applicable).
• Test the brake pedal for a firm feel; if spongy, repeat the bleeding process.
• Drive the vehicle slowly for 0.6 miles (1 km) to confirm consistent braking performance.
• Dispose of old brake fluid at a recycling center.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• YouTube