Vacuum assisted hydraulic brake systems are subject to the following requirements and limitations:

(1) Supply system.

(a) When equipped with a protected vacuum reservoir, there must be no more than three inches drop in vacuum in one minute after turning off the engine.

(b) When not equipped with a protected vacuum reservoir, a slight drop of the brake pedal should be felt after starting the engine when moderate pressure is applied to the pedal. If a slight drop of the pedal does not occur, the vacuum system must be deemed to be defective.

(c) Hydraulic fluid must be maintained in excess of 50 percent of the brake master cylinder capacity.

(d) The hydraulic portion of the system must pass the following test procedures:

(i) With the engine off, a hard brake pedal application must be made.

(ii) Pedal pressure must be reduced but not released.

(iii) Pedal pressure must be gradually reapplied and pedal reserve must be checked.

(iv) No pedal reserve drop should occur. Any such drop in pedal reserve must cause the system to be deemed defective.

(2) Brake assembly.

(a) Adjustment of all brakes must comply with the manufacturer's recommended specifications.

(b) Brake system components must meet all the requirements of RCW 46.37.360, and brake drums will not be cracked or broken to the extent that such crack or break appears on the outside of the drum.

(c) Brake lining, pad friction surface, or braking surface of the brake drum or rotor must not be contaminated with grease, oil, or brake fluid.