Ask the Mechanic

WHY DOES MY STEERING WHEEL SHAKE? Hello Paul, my Kia Sportage steering violently shakes when I brake at high speeds. This problem has progressed over a few weeks. What could be the cause? Babirye Hello Babirye, steering wheel shakes at high speeds is quite disconcerting and can cause loss of control. There are five common causes of steering wheel shakes and you will need a mechanic to inspect and decide the culprit in your case. Areas to check include warped brake discs (rotors), wheels out of balance, worn out steering tie rods, worn out CV axle joint or worn out upper control arm bushings or suspension ball joints. Warped brake discs are damaged by heat during emergency or severe braking. This makes the brake disc surface uneven, which causes juddering and shaking of the steering when you brake. Using a vernier caliper, you can detect uneven sections of the disc. You need to replace the discs if their surface is unevenly worn out. Wheels excessively out of balance will vibrate and shake the steering as you speed along. Wheel balancing at a tyre dealer will rule that out. Worn out tie rods will allow a play between the spindle and the steering, which will cause steering shake. An inspection of the tie rods after dismantling will confirm their state. Avoid remedial pressing of tie rods if they are worn out, just replace them. Worn out CV joints tend to bend, which causes steering shakes since they transfer power from the transmission to the wheels. A visual inspection will determine if they are the culprits. On vehicles with upper and lower control arms such as yours, worn out cone bushings and wandering suspension ball joints will cause steering shakes at faster speeds. A visual inspection after dismantling is necessary to confirm this problem. MY CAR’S ENGINE KEEPS STOPPING I drive a Subaru Forester 2008 model. A few days ago, the engine started stopping especially while driving at low speeds such as during traffic jam. My mechanic thinks the computer is faulty. However, there is no check engine light. What could be the fault? Eseza. Hello Eseza, whereas it is possible that faulty engine management system components such as the crank shaft position sensor can cause erratic engine stalling, there are other mechanical components such as a clogged fuel filter, faulty throttle idle air control valve, aged spark plugs or dirty air filter that can also cause the same problem. A diagnostic check can help to identify or rule out an engine management component failure. In the absence of a faulty electric component, your service provider can consider checking the fuel filter maintenance status, spark plugs, air cleaner element and the air intake system for a leak on the intake pipe between the air flow sensor and throttle potentiometer. HOW CAN I EFFECTIVELY CONTROL MY CAR WHILE NEGOTIATING CORNERS? Hello Paul, I drive a Toyota Prado with a manual gearbox. Kindly advise which gears I should use when driving fast through a corner on the highway. Normally I feel uncomfortable as I drive through corners and feel as if the car is veering off the road. Asuman Hello Asuman, when driving fast on the highway, the motion forces or momentum will keep your vehicle moving in a straight line and will counter your effort to turn the vehicle in a curve or corner. This is more difficult when you are driving fast and the road surface is wet or loose with gravel. The tendency is the vehicle to lose road grip or start to skid as you turn sharply at high speed. You ought to use a deliberate technique when driving through sharp curves or corners on the highway in order to avoid skidding or losing control of your vehicle. Slow down by taking your foot off the accelerator or braking slightly while still in the straight line. Any steering action should be gradual to avoid losing control or skidding. Modern cars with traction control or electronic stability programme (ESP) will monitor wheel speeds while stiffening the steering to avoid over steer. ESP selectively applies brakes and down shifts using brake assist to slow the car. You can simulate the ESP counter measures by shifting from higher to lower gears, for example from five to four to three then to two. Do this while controlling the steering angle and accelerating after the midpoint of the curve or corner and gradually centering the steering as you get back to the straight line after the corner. MY CAR EMITS WHITE SMOKE THAT SMELLS LIKE ROTTEN EGGS Hello Paul, my Toyota RAV4 2000 has started emitting whitish smoke from the exhaust with a horrible smell of rotten eggs. Now, the car is weak when driving uphill. Is my engine damaged? Kaggwa Hello Kaggwa, white exhaust smoke is a sign of your engine burning coolant. This is often the result of a warped cylinder head gasket after severe engine overheating episodes. This gasket ensures that all fluids such as coolant and oil are kept in their respective galleries to avoid intrusion in the combustion chamber. When coolant leaks into the combustion chamber, it is burnt together with fuel, which results into white exhaust emission. Burning coolant prevents total combustion of fuel. The resultant unburnt fuel will end up in the exhaust system where it accumulates and burns in the very hot honey comb-like catalytic convertor (CAT). The ammonia-like smell you describe is a confirmation of catalytic convertor damage and a potential damage of the engine as the CAT gets blocked and restricts emission of exhaust. No wonder you are experiencing reduced engine performance. Visit a garage as soon as possible to have the head gasket and catalytic convertor inspected for replacement. Send sms: mycar (space) your comments and questions to 6933 or email them to: [email protected]