The brake pedal is not only the device of stepping on but also a device with which the car engine is stopped. When you step on the brake pedal, it makes hydraulic fluid flow in brake lines to stop wheels. The extent that the car will be decelerated when brakes are applied depends on how hard you press down on the foot.
Why brake pedal becomes hard and car does not start? This can be caused by a number of things, here are a few reasons:
The ignition switch/ignition lock cylinder needs to be replaced. This will happen most often if the key gets stuck in the ignition or it breaks off inside of it. If this happens, you may have to have it towed into a shop because they will have to remove the whole assembly from under the dash in order to get at the ignition lock cylinder and replace it. The good news is that you should only have to pay your regular diagnosis fee for this work, even if they end up replacing a part that was not broken before they started working on your car, because it is a safety hazard to drive the car if the switch does not work. Once it has been replaced, your brake pedal should go all of the way down and you should be able to start your car without any problems.
Brake fluid level
The brake fluid level in the master cylinder may have dropped below a safe level due to normal wear and tear on the vehicle or from an accident that damaged a brake line/portion of the hydraulic system. When this happens it will cause a much higher than average amount of effort exerted by you when you press down on the brake pedal because there isn’t as much fluid pushing against those pistons inside that have been activated by your foot pressure against them. In order to fix this problem, you need to have the brake fluid in the master cylinder inspected and refilled, or replaced if necessary.
There could be a problem with the brake booster causing your vehicle not to respond to your effort when you press down on the brake pedal. This is more common on older vehicles than newer models because of advances made in technology, but it can still happen with really old cars too. If this is the case, you will notice that there isn’t much resistance when you press against the brake pedal at all and you will have no choice but to use all of your leg muscle strength just to get any braking power out of your car. You should definitely take it into a shop immediately so they can see why there is such little applied by your foot onto the brake pedal.
The brake fluid in the master cylinder may be evaporating because of an internal leak developing in one or more of the hydraulic lines, valves, or other components. Over time this will cause the pressure inside of the master cylinder to drop dramatically and could potentially lead to total loss of braking power if it is bad enough. Unfortunately, there isn’t really anything you can do about this problem on your own once it develops other than to get it repaired so that you can safely operate your vehicle again.
Brake not releasing
You might have a problem with the parking brake not releasing which could prevent you from being able to start your vehicle even though it has ignition switch/ignition lock cylinder problems, but usually only if it has an automatic transmission. If your parking brake is stuck on, it will prevent the vehicle from being able to roll freely which will cause it not to be able to start. You should have this inspected immediately because of the safety hazard of keeping the parking brake on when you are driving down the road.
There are many causes for this issue and your mechanic can help walk you through them so they know what to look for exactly if they find that one of these issues needs some attention. It could potentially save you quite a bit of money by avoiding unnecessary parts replacements if it turns out that there was nothing actually wrong with any major parts before testing them in the first place.