Villager V6-201 3.3L SOHC VIN T SFI (1999)
Brake Master Cylinder: Component Tests and General Diagnostics
Brake Master Cylinder
Normal Conditions
The following conditions are considered normal and are not indications that the brake master cylinder is in need of repair.
Condition 1: During normal operation of the brake master cylinder, the brake fluid level in the brake master cylinder reservoir will rise during brake
application and fall during release. The net brake fluid level will remain unchanged.
Condition 2: A trace of brake fluid will exist on the power brake master cylinder mounting flange. This results from the normal lubricating action of
the brake master cylinder bore and seal.
Condition 3: Brake fluid level will decrease with brake shoe and lining wear.
Abnormal Condition
Changes in brake pedal feel or travel are indicators that something could be wrong in the brake system.
Bypass Condition Test
Check the brake fluid and fill to specification. With the brake master cylinder cap removed, observe the fluid level when the brake pedal is slowly
depressed for one stroke and then quickly released. If the fluid in the brake master cylinder reservoir rises while the brake pedal goes down and drops
when the brake pedal is released, but the net (overall) fluid level in the reservoir remains unchanged, the brake master cylinder is bypassing.
Bypass Conditions Test
Check the brake fluid and fill to specification. With the brake master cylinder cap removed, observe the fluid level when the brake pedal is slowly
depressed for one stroke and then quickly released. If the fluid in the brake master cylinder reservoir rises while the brake pedal goes down and drops
when the brake pedal is released, but the net (overall) fluid level in the reservoir remains unchanged, the brake master cylinder is bypassing.
Compensator Port Check
If it is believed that the brake master cylinder is failing to return to the fully released position, proceed as follows: Raise the front of the vehicle and
support it on safety stands. With the brakes off, attempt to rotate both front wheels by hand. To minimize brake pad drag, rock the wheel on the wheel
hub as it is rotated. If an excessive amount of brake drag is apparent on both wheels, the brake master cylinder may not be returning to the released
position. If an excessive amount of brake drag is apparent at only one wheel, it indicates a possible seized caliper piston. Check the Brake Pedal
Position (BPP) switch adjustment to make sure the switch is not holding the brake pedal in the partially applied position. Loosen the nuts attaching the
brake master cylinder to the power brake booster, and pull the brake master cylinder away from the power brake booster. If the brake drag disappears,
install a new power brake booster. If the cylinder brake drag continues, install a new brake master cylinder.
Compensator Port Test
If it is believed that the brake master cylinder is failing to return to the fully released position, proceed as follows: Raise the front of the vehicle and
support it on safety stands. With the brakes off, attempt to rotate both front wheels by hand. To minimize brake pad drag, rock the wheel on the wheel
hub as it is rotated. If an excessive amount of brake drag is apparent on both wheels, the brake master cylinder may not be returning to the released
position. If an excessive amount of brake drag is apparent at only one wheel, it indicates a possible seized caliper piston. Check the Brake Pedal
Position (BPP) switch adjustment to make sure the switch is not holding the brake pedal in the partially applied position. Loosen the nuts attaching the
brake master cylinder to the power brake booster, and pull the brake master cylinder away from the power brake booster. If the brake drag disappears,
install a new power brake booster. If the cylinder brake drag continues, install a new brake master cylinder.
Non-Pressure Leaks
An empty brake master cylinder reservoir condition may be caused by three types of nonpressure external leaks:
Type 1: An external leak may occur at the brake master cylinder filler cap because of improper positioning.
Type 2: An external leak may occur at the mounting end of the brake master cylinder because of a bore end seal leak.
Type 3: An external leak may occur in the rubber hoses between the brake master cylinder reservoir and brake master cylinder. Check the rubber
hoses for damage. Repair as necessary.
