THEM’S THE BRAKES
Panic-stop pedal shake is ABS
Whether you’re a new driver or driving a new type of vehicle, there are always questions that lead to unnecessary trips to a service repair facility. Here are some of the top inquiries service consultants and techs get on a regular basis.
Q What’s that liquid dripping from under my car?
A On vehicles, there are two sources of dripping liquid that are perfectly normal.
The first is the air conditioning system. Condensation that collects on the HVAC’s evaporator core, in the heater box behind the dash, has to be directed away from sensitive electronics, wiring, and carpeting. All AC-equipped vehicles have a drain pan in the heater box with a tube that to let water drip out, usually just behind a front wheel. The hotter and more humid the weather, the more water that drips.
The second source is the exhaust system. Water is a natural byproduct of gasoline combustion and in most cars, a drain hole at the rear of the muffler stops this water from pooling inside, which can lead to premature corrosion. It’s most noticeable in cold weather.
Q What’s that tinkling noise under the hood?
A If you’ve got a good ear, you’ll hear a tinkling noise — the sound of engine metals expanding with heat — for a few minutes after the engine is turned off. An engine’s internal temperature spikes for a short time after it’s turned off as the coolant circulation stops.
Q Why are my brakes noisy even after I just had them done?
A Brake sounds are one of the biggest service counter noise complaints, but some are unavoidable. Slow parking lot manoeuvres that involve “feathering” the brake pedal will induce light groans that are normal. If a vehicle sits idle for more than a few days (even just overnight in damp weather) expect a little light grinding noise for the first few brake applications as surface corrosion on the discs or rotors is worn away by the brake pads.
Q Why does my brake pedal vibrate on urgent stops?
A If you’re driving a vehicle equipped with anti-lock brakes for the first time, the operation can feel a little weird. When anti-lock brakes are activated, they apply the hydraulic forces to the wheel units in rapid pulses, which get transmitted back to the foot pedal. It’s a good idea to try this out on a traffic-free, snowcovered side street or parking lot to get used to the operation and to learn that you have full steering control during panic stops.
Q Why does my air conditioning get warm when passing a car?
A Most modern engines have a computer control that turns off the AC compressor on full-throttle acceleration to reduce engine load. The AC quickly resumes when you lighten up on the gas.
Q Why do my windows fog up or take so long to defrost?
A Many drivers engage the recirculation control on their
If your vehicle’s refrigerant gas charge is really low, the AC compressor ... will cycle off and on rapidly.
vehicles’ HVAC systems in the winter, seeking better heat. When the shutters to the freshair intake are closed, the cabin air quickly becomes laden with moisture from wet floor mats and passenger breathing. Turn off the recirculation control and lower the fan setting by one speed from high and you’ll soon see clearly.
Q Why is my AC warmer?
A This is more of a summer heat-wave question. The hotter the weather and the stronger the sunshine, the less effective an HVAC system becomes. If you take it into the shop for a checkup, about the only thing the tech will do is hook up a recharge station to check for leaks and measure the amount of refrigerant gas in the system, then present you with an invoice (unless a leak or problem is found).
On a day with temperatures in the mid 20s, your HVAC temp output (measured at the centre dash vent) should be between seven and 10 degrees. When it’s hotter, the door glasses and windshield can push the limits of the AC’s effectiveness. If your vehicle’s refrigerant gas charge is really low, the AC compressor (attached by belt to the engine’s front) will cycle off and on rapidly.