1999 Chevrolet Astro Brake Service (ONLINE REPAIR MANUALS)

Delco Master Cylinder

When performing the following procedures, refer to Figs. and noting that the composite reservoir may vary in design.

Disassemble

• Remove master cylinder from vehicle.
• Remove reservoir cover and diaphragm. Discard old brake fluid in reservoir.
• Inspect cover and diaphragm. Replace if cut, cracked or deformed.
• Remove fluid level switch and proportioning valve assembly, if equipped.
• Depress primary piston and remove lock ring.
• Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then apply compressed air into secondary fluid outlet t...

Excessive Pedal Travel

• Worn brake linings.
• Disc pads knock back after cornering or rough road travel.
• Piston and linings not properly seated or positioned.
• Insufficient fluid in system.
• Loose wheel bearing adjustment.
• Damaged or worn caliper piston seal.
• Improper booster pushrod adjustment.
• Pads out of flat more than .005 inch.
• Rear brake automatic adjusters inoperative.
• Improperly ground rear brake shoes.

Brake Roughness Or Chatter; Pedal Pumping

• Excessive lateral runout of rotor.
• Rotor excessively out of parallel.

Excessive Pedal Effort

• Frozen or seized pistons.
• Brake fluid, oil or grease on ...

Battery Ground Cable

Prior to service disconnect battery ground cable and isolate as required.

Radio Security System

Theftlock

If the Theftlock system is active when battery power is interrupted, the customers security code must be entered to restore proper function of the radio. To unlock a secured radio after power loss, proceed as follows:

• "LOC" appears with ignition in On position.
• Press "NM" and "000" will appear on display.
• Press "NM" again to make last two digits agree with security code.
• Press "HR" to make first 1 or 2 digits agree with security code.
• Press "AM-FM" to select code entered. "SEC" wi...

Service Brake

These brakes have self-adjusting shoe mechanisms that ensure correct lining-to-drum clearances at all times. The automatic adjusters operate only when the brakes are applied as the vehicle is moving rearward or when the car comes to an uphill stop.

Although the brakes are self-adjusting, an initial adjustment is necessary after the brake shoes have been relined or replaced, or when the length of the adjusting screw has been changed during some other service operation.

Frequent usage of an automatic transmission forward range to halt reverse vehicle motion may prevent the ...

Manual Bleed

• If vehicle is equipped with power brakes, remove vacuum reserve by applying brakes several times with engine off.
• Fill master cylinder reservoirs with suitable brake fluid. Ensure to always keep master cylinder reservoirs at least half full during entire bleeding procedure.
• If master cylinder is suspected to have air in the bore, it must be bled first. To bleed master cylinder, proceed as follows:
• Disconnect forward brake pipe connection at master cylinder.
• Allow brake fluid to fill master cylinder bore until it begins to flow from forward pipe connector port.
• Connect ...

When working on or around brake assemblies, care must be taken to prevent breathing asbestos dust, as many manufacturers incorporate asbestos fibers in the production of brake linings. During routine service operations, the amount of asbestos dust from brake lining wear is at a low level because of a chemical breakdown during use and a few precautions will minimize exposure. Do not sand or grind brake linings unless suitable local exhaust ventilation equipment is used to prevent ...