Chrysler Repair: No power brake/hissing sound in cabin: LH car, master brake cylinder, power brake booster

Question
QUESTION: I was sitting at a red light the other day (with my foot on the brake) and I hear a dull "POP" sound and then hissing, like air leaking out of a hose. The hissing stopped when I let off the brakes. Now I have no power brakes and I hear the hissing every time I press the brake pedal, but not using the e-brake. Is this most likely the booster, or is it possibly just a broken hose? Thanks

ANSWER: Hi Darin,
It sounds like the vacuum hose to the power brake booster can has come loose or gotten a hole in it. So inspect that hose's fittings and its condition. The canister should be at the firewall near the master brake cylinder and it connects to the intake manifold.
Roland

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QUESTION: Thanks Roland. I removed the vacuum hose and there doesn't appear to be any holes or tears. The check valve that plugs into the booster can appears to be functioning as well. I am able to pass air through the hose by blowing into the valve directly, but not by blowing into the end that connects to the manifold. I can only hear the hissing sound from inside the car (right above the brake pedal), not from the engine compartment when someone else is holding down the brake pedal. Any thoughts?

ANSWER: What is the year/make/model?

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QUESTION: 1999 Chrysler LHS

Answer
Hi Darin,
It sounds to me like your power brake booster is defective as you have no power brake action and the noise sounds like it is coming from the pedal area. The booster is actually mounted on the firewall and the master brake piston rod goes right through the middle of it and into the master cylinder which effectively seals that central annulus of the booster from the engine compartemnt. If it were leaking at that point I can see why it would be louder in the cabin than in the engine compartment. Absent any other vacuum devices in that area it all adds up to a bad booster. It is a bit complicated to remove, so if you don't have a manual I wouldn't try it. I can xerox copy the 3 pages that cover the process and postal mail them to you. Just give me a postal address.
Roland