The first piece of advice here is to not drive the car at all until this problem is fixed. A car with faulty brakes is one of the most dangerous situations you can find yourself in, and it’s just not safe to even attempt to move it, even to relocate it on the driveway. The problem could get a lot worse very quickly, leaving you with no brakes at all. And even if it doesn’t get any worse, your limited braking capacity could make an emergency situation much, much worse.

The noise is probably not brake-line pressure escaping, since you don’t have falling brake fluid levels. At which point, my suspicion becomes that the brake master cylinder is at fault. This is a device that uses vacuum from the engine to assist you to push the brake pedal. If the diaphragm inside the booster fails, you will might hear the vacuum escaping, with a hissing noise. Even if the booster is intact internally, a simple hose that connects the booster to the engine could have split and caused the leak. Until it’s fixed, though, you won’t have full braking power and that’s, obviously, very dangerous.

It begs the question did you drive the car before you bought it. If so was the steering heavy, and has it changed since you drove it? It shouldn't be as heavy to steer as you suggest yours is. I would suggest it's a failure of the power steering system, and that you should have it checked.

Toyota says it will investigate the issues reported by Colin Smith if our reader gives his consent, and we are keen to hear the outcome of any investigation that takes place. Your mechanic could well be on the money when he suggest it could be a computer problem.