It’s a frightening experience when you’re driving and you notice a distinct burning smell – only to realise that there’s smoke coming into your car!
There can be a few reasons why this happens, but most of the time, your brakes are to blame. If your brakes are smoking, it’s best to stop driving until a technician has fixed the problem. To help you understand why your brakes might be producing smoke, we’ve rounded up a few of the common causes and some warning signs to watch out for.
Disc brakes are made up of a calipers, discs and pads. When you apply the brakes, brake fluid is forced into the caliper, which pushes the piston and causes the brake pads to move inwards against the disc. The friction generated between the pads and discs causes the car to slow down and stop.
Drum brakes are often found on the rear of some cars. Instead of a caliper to move the brake components, the ‘drum and shoe’ system uses a wheel cylinder. When you put your foot on the brake, the fluid is forced into the cylinder, which causes two small pistons to push the brake shoes outward. As the shoes move outwards, they come into contact with the internal surface of the brake drum. The friction between the shoe and drum helps your car slow down or stop.
Your brakes are exposed to the elements, so it’s obvious that dirt, brake dust and corrosion will build up over time. The build-up of dust on the pad carriers can cause the brake pads to stick to the disc. When this happens, the brakes can’t return to their normal position and the wheel doesn’t spin freely. The constant friction creates a lot of unnecessary heat which often results in a bad smell and sometimes smoke. This really isn’t good for your brake system as it can prematurely wear down different parts of your brakes.
Another common issue is a seized caliper. If your caliper has seized, it means that the piston is stuck and the brake pad is pushed against the rotor. Basically, your brakes are constantly applied while driving, even if you aren’t using them. In a similar way to stuck brake pads, the constant friction causes unusually high temperatures that are likely to result in a burning smell and smoke. When working properly, brake disc temperatures can reach 200°C, while sticky or seized brakes can often reach temperatures exceeding 500°C!
The wheel cylinders are an important part of your drum brakes. If the wheel cylinder has seized, this means it is stuck in place and is continuously pushing the shoe pads against the inside of the drum. A wheel cylinder locked in place will have the same effect as a stuck piston – meaning that you’re driving with your brakes engaged when you aren’t using them. Unlike disc brakes, you won’t be able to see if the wheel cylinder has locked the shoes against the drum lining. If you suspect that a burning smell or smoke is coming from your rear drum brakes, get your car checked by a technician soon. The longer you leave it, the more likely you are to cause more damage to your brake system.
Apart from smelling a smoky odour or seeing smoke, wheel discoloration is one other indication that there’s a problem with your brakes. Look for a rusty stain on your alloy wheel or wheel trim. The rusty colour is the result of brake dust from the disc, which has been baked onto the wheel due to excessive heat.
There’s no real way to avoid a build-up of brake dust as your brakes are exposed, but you can prevent it from becoming a problem. During your car’s annual service, you may be advised to have a ‘brake clean’ or a ‘brake deglaze’. This advice is usually given when one of our technicians notice that the wheel is dragging or isn’t spinning freely. While a brake clean may not seem crucial at the time, it could potentially save your brakes from smoking.
Your car’s braking system is essential. After all, it’s what stops your car and keeps you and your family safe. If you ever have any doubt about the safety of your braking system, call your breakdown service immediately and do not use the car until it’s been checked by the professionals at our service centres.