Our trusty mechanical engineer troubleshoots these possible problems with braking systems.

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Our trusty mechanical engineer troubleshoots these possible problems with braking systems.

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Keeping your brakes in good nick is crucial to active safety on the road, because they can help you to avoid crashing into something or someone. 

I am driving a seven-year-old Japanese car. I observed recently that when the vehicle is stopping, there is a “tuck tuck tuck” sound coming from the engine compartment or front wheels. 

What is the cause and what are the consequences? Is the problem serious or should I wait till it is more obvious to do something since the car behaves normally at other times?

This is not an uncommon problem and is caused by an excessively worn brake disc. 

Usually, when the disc is badly scored (grooves on the surface) or gets warped over time, workshops recommend that you have the disc surface machined or skimmed to remove imperfections and unevenness. 

There is nothing wrong in doing so and it is, of course, the cheaper alternative to replacing with new discs. 

The problem is when the symptoms appear again after prolonged use, you might end up with another mechanic or workshop with no record of what was previously done. Skimming the second or third time will ultimately lead to disc thickness below the allowable limit. During braking, the brake piston will then need to slide out further than normal, leading to the piston “rocking” as the brake pressure is applied. 

At this stage, the only remedy is to replace the brake discs. And do it immediately, before your brake pistons get damaged. 

What does it mean when my car’s amber anti-lock braking system (ABS) warning light comes on and stays on when the engine has started? 

I am worried this means some sort of impediment to the braking system, which could lead to total loss of braking capability. 

ABS was developed by Bosch, together with Daimler, and was first introduced in a production car 40 years ago in 1978. 

ABS, as its name suggests, prevents the wheels from locking up. If wheels lock, the car skids and the driver loses control of the car, with potentially dangerous consequences. 

You must send your car to a workshop as soon as possible. The warning light, however, does not mean the brakes might fail completely. You will still have normal braking performance, but in an emergency, the anti- lock function may not work. 

My car is less than six months old. When I drove to Malaysia two weeks ago, I felt a vibration whenever I braked firmly from any speed above 130km/h. 

Is this normal? If not, what should I tell the service adviser when I send the car for maintenance? 

To answer your first question, no, it is not normal. 

Vibration during hard braking is most commonly caused by uneven brake-disc surface, most likely from the front discs, as the rear brake effect is only about 30 percent of total braking force. 

Often, this can happen in a new car (up to a few weeks/months old) if it has not been run-in properly. 

When running in, excessively hard braking should be avoided, at least in the first 1000 kilometres or so. 

If you have been diligent with the running-in of your new car and still experience the vibration, you should send it to the dealer as soon as possible. 

Since high-speed brake tests are not possible in Singapore, ask the service adviser/department to measure the “flatness” of the disc using a dial gauge. 

There is always the possibility that brand-new brake discs have a manufacturing defect that could cause the vibration.