Subject: hig pitched whistling under the hood
Question:

I know that you are a Mitsubishi expert but maybe you can help me. I have a 1986 Toyota Corolla. When I first press the accellerator after I crank my car there is a high pitched whisling under the hood. The whistling is constant unless I press the brake pedal. The only time the whistling stops is when the brake pedal is pressed or the ignition is off. Can you help me? 

Answer: Michelle,
If this noise occurs while you're not moving but the engine is running, then your problem could be a leak or crack in your brake booster diaphram or master brake cylinder. When your engine is running, it draws a vacuum which assists in helping you stop your car via your brake pedal. Hence, that's why they call them power brakes. The braking system is a sealed system which needs to maintain certain amount of pressure. If there is a leak in the system, air could rush in because air is a lot less dense than brake fluid. If air is entering the system where it's not supposed to, that could create a whistling noise.

If you also notice the sound when the car is in motion, you may have a stuck brake caliper, loose drive belt, or even a leak in your air filter housing. Have a mechanic check out the braking system for any leaks. Provide them with as much info as possible.
Good luck!