Questions and Answers

Honda Brake Fade Q. I own an 1989 Honda Prelude si 4 cylinder engine. Manual transmission, 101k miles, fuel injected, P/S, A/C, cruise. When the A/C is on, the brake pedal wants to fade and drop lower than normal. When the A/C is off, the brakes work fine. I have had in shop and they find nothing wrong. Any advice would be appreciated. Thanks, Kelly

A. In this case I would have to look at the brake vacuum booster, specifically the vacuum booster check valve. The brake booster check valve is designed to allow vacuum storage in the brake booster. This permits consistent power brake operation during low vacuum situations. The check valve is a one-way valve, allowing vacuum to be applied in only one direction only. If this is bad, it will cause the problem you describe.

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