OEM 2004 Chevrolet Astro Brake Master Cylinder

2004 Chevrolet Astro Brake Master Cylinder Parts Questions & Experts Answers

• Q: How to bench bleed the brake master cylinder on 2004 Chevrolet Astro?

  A: To bench bleed Brake Master Cylinder remove the mounting flange and put it inside of a bench vise with the back of the primary Piston. Replace the master cylinder reservoir cap and diaphragm and attach appropriate fittings on the master cylinder ports for the necessary flare seat and hose attachment. Connect transparent hoses to these fittings and run them into the master cylinder reservoir. Add delco supreme ii, gm p/n 12377967 (Canadian P/N 992667), or equivalent dot3 brake fluid to the reservoir at least half full from a clean, sealed container, making sure that the ends of the hoses are completely submerged. Employing a round-ended, smooth tool, press and let go of the primary Piston down to an approximate 25mm (1 inch) several times and view the flow of the fluid from the ports. When air is also bled from the primary and secondary pistons, the effort needed to depress the primary Piston will be greater and the travel will be less. Repeat the same process until free flow of the fluid occurs from the ports without accompanying air bubbles. Then evacuate the removal of the transparent hoses from the reservoir, installing the master cylinder reservoir cap and diaphragm and then removing the fittings with the hoses from the ports, wrapping the master cylinder with a clean shop cloth so that spills can be avoided. Last but not the least, unstuck the master cylinder from the vise.