Hello can anyone help me. I test drove a 2004 Mustang GT and when I press on the brakes it is normal and the brakes work fine. However, if I press on the brake hard I hear a hissing noise that increases in volume the harder I press on the brake. In addition if I press on the brakes hard the idle drops.

Does anyone have any ideas? Is this normal? Thanks.

 

Nice work--thank you for sharing-
Thanks so much for this. I appreciate the effort. It really helps a lot.
Glad to hear you're using this: I plan to keep it much more aggressively up-to-date than has been the case in the past, but don't hesitate to let me know if you find errors or need clarifications.

 

Sounds like it could be an issue with the brake booster.