Here's a general procedure. Always consult your owner's manual for the specific bleeding order for your vehicle, as it may vary slightly from the common method. The order is critical to ensure proper air expulsion.
Materials Needed:
* Brake bleeding fluid (DOT 3 or DOT 4, check your owner's manual)
* Clear tubing (about 3-4 feet long)
* A wrench that fits your bleeder valves (usually 8mm or 10mm)
* A container to collect the old brake fluid
* A helper
Procedure:
1. Safety First: Park the van on a level surface, engage the parking brake firmly, and ensure the engine is off. Wear safety glasses.
2. Locate Bleeder Valves: Identify the bleeder valves on each wheel caliper (front and rear). They are typically small nipples near the top of the caliper.
3. Check Brake Fluid Level: Before starting, check the brake fluid reservoir level and top it off to the "MAX" line with the correct fluid type. Do not overfill.
4. Bleeding Order (Important!): The most common bleeding order is Rear passenger side (right), Rear driver side (left), Front passenger side (right), Front driver side (left). Again, check your owner's manual to confirm the correct order for your specific Astro. This order helps push air out of the system most effectively.
5. Attach Tubing and Container: Attach one end of the clear tubing to the bleeder valve and the other end to the container. Make sure the tubing is securely attached to prevent leaks.
6. Bleeding Process (with helper):
* Have your helper pump the brake pedal several times and then hold it down firmly.
* While the pedal is depressed, carefully open the bleeder valve one full turn with your wrench. You should see old brake fluid flowing through the tubing.
* Close the bleeder valve as soon as the fluid flow stops (while your helper still holds the pedal down).
* Have your helper release the brake pedal.
* Repeat steps 6-8 several times for each wheel until you see only clean, clear fluid coming out with no air bubbles.
* Keep the brake fluid reservoir topped off throughout the bleeding process to prevent air from being sucked in.
7. AWD Considerations: Because of the AWD system, you may need to bleed the rear differential as well. This requires accessing a bleeder valve on the differential itself. Your owner's manual should provide information on this, or consult a repair manual. This step isn't always necessary but is advisable to ensure complete system bleeding.
8. Test: After bleeding all four wheels (and the differential, if applicable), check the brake pedal for firmness. If the pedal is still spongy or feels soft, repeat the bleeding process, paying close attention to the possibility of a leak in the system.
9. Final Check: After the bleeding is complete, top off the brake fluid reservoir to the "MAX" line. Check for any leaks around the bleeder valves and wheel cylinders.
Important Notes:
* Air in the lines is a serious problem and can lead to brake failure. If you are unsure about any step, consult a professional.
* Use only the correct type of brake fluid. Using the wrong fluid can damage your brake system.
* Brake fluid is corrosive. Clean up any spills immediately.
* If you still have problems after bleeding, there may be a more serious issue with your braking system requiring professional attention.
This guide provides general instructions. Always refer to your vehicle's owner's manual for specific instructions and recommendations. If you are not comfortable with this procedure, have a qualified mechanic perform the brake bleeding for you. Your safety is paramount.
