If a technician cannot get any fluid to come out of the disc brake caliper bleeder screws when using a pressure bleeder, what is the MOST LIKELY cause?

• A. Clogged brake lines
• B. Master cylinder failure
• C. Metering valve release button not activated
• D. Worn brake pads

Answer: (C)

The most likely cause of not getting any fluid to come out of the disc brake caliper bleeder screws, especially when using a pressure bleeder, is related to the metering valve release button not being activated. The metering valve is a component in the brake system that helps to control the brake fluid pressure to the front brakes. If the valve is not released, it can restrict fluid flow to the caliper, preventing fluid from reaching the bleeder screws.

When using a pressure bleeder, it's essential that the metering valve is in the correct position to allow fluid to flow freely. If the valve is stuck or the release button isn't activated, this can cause the system to be sealed off, resulting in no fluid pressure at the calipers and thus no fluid expelling from the bleeder screws.

In contrast, a clogged brake line would usually result in pressure buildup and possible fluid leaking elsewhere, while complete failure of the master cylinder might still allow some fluid to reach the bleeders under certain conditions. Worn brake pads, although they can affect braking performance, would not prevent brake fluid from reaching the calipers during the bleeding process.