If you feel your Porsche 944 Turbo brake booster isn't working the way they should, then there's a reason to be concerned. Driving a Porsche 944 Turbo with a brake pedal that is hard to depress is dangerous for you and for the vehicles around you on the road regardless of the speed you are driving. While a brake going berserk because of a faulty brake booster isn't an everyday occurrence, it is important that you know how to diagnose and troubleshoot your brake booster in case it happens to your car.
A problem most common to brake booster is vacuum leaks due to damaged or worn-out pistons or diaphragm, valve, seals, and rubber hose. When this happens, you still have your brake working, but with little or no assist from the power brakes, forcing you to apply more pressure to the brakes just to make the vehicle stop. To check for vacuum leaks, depress the brake pedal five times or until the brake is hard to depress. Start the engine with your foot still on the brake pedal. If the pedal goes down slightly after you start the engine, your brake booster is no longer working. Fix the problem by replacing the entire unit with a new or rebuilt brake booster.
When the vacuum line attached to the brake booster is punctured, it lets the air out and produces a whining noise every time you step on the brake pedal while driving. Replace the vacuum line to solve the problem and avoid damaging the brake booster.
This is the sign that your brake booster is out. Your brakes will still work, but you have to apply greater pressure to the pedal just to make your vehicle slow down or stop. Vehicle owners often say that they literally have to stand on the brake pedal or use two feet just to make the brakes bite. If you experience this, you should replace the brake booster right away.