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Ask the Mechanic: Why does my car make crackling noises?

Hello Paul, my Toyota Premio makes strange crackling noises when I turn the steering. These noises started when a mechanic raised my car with spacers. He has failed to find the cause of the noise after replacing shock absorbers and all bushes. What can I do?

Derrick

Hello Derrick, the noise you describe must have something to do with the spacers that were fitted to the suspension. Spacers are block discs that are fitted between the car suspension coil spring seats or mountings and the car body. They are meant to raise the car profile and are a common practice in our garages used to control damage to the car engine underside when driving over uneven roads and humps.

This practice may help to overcome ground clearance challenges, but it causes other problems such as stress and damage to suspension, altering the safe handling or ride characteristics of the car. The crackling noise as you turn the steering is most likely stress or damage to the shock absorber mounting, which ideally is designed to be the spring seat and cushion between the car spring and body panel.

Installing a spacer plate between the shock absorber mounting and body puts uneven load and pressure on the mounting, which causes its rubber component to tear and eliminate its role as an impact insulator. This way, the springs and shocks take stress of forward and turning movements, hence the crackling noises. Soon, you will most likely need to replace the shock mountings as well as other suspension components which will prematurely wear out as a result of being stressed by the spacers.

Raising the car with spacers alters its safe handling and ride quality because it restricts the primary role of suspension which is to help the car absorb or adapt to road imperfections such as humps, sudden depressions or sharp bends. Suspension helps the car to recover as it drives through those sections of the road. Altering the suspension matrix with spacers can cause an accident when you lose control while driving fast through sharp corners. This is because the performance of your suspension will have been altered.

MY CAR’S PERFORMANCE HAS DECLINED

Hello Paul, my Toyota RAV4 2007 makes a loud rattling noise when I start it in the morning or accelerate it uphill. The car engine power also seems to be erratic yet I have replaced the in-tank fuel filter and spark plugs. What could be the cause of this noise and poor engine performance?

Woods

Hello Woods, the rattling noise is most likely caused by a damaged timing chain kit in the engine. Consider replacing the timing chain kit (chain, sprocket, tensioner, plastic guides and timing gear). The timing chain is an important component of an internal combustion engine and it is made up of metal links that run along a set of gears designed to rotate the camshafts and crank shaft. These ensure that the engine valves and pistons open and close in sync to allow timely ignition and combustion or burning of fuel to create drive, which turns the transmission and wheels.  Timing chains ensure that the fast-moving internal combustion components such as pistons and valves work without colliding to cause costly damage. If the timing chain breaks or loosens due to age or damage, engine performance is altered and costly components get damaged.

Ordinarily, the timing chain is encased in the engine and bathed in engine oil as other moving metallic components. The quality of engine lubrication or engine oil and filter used is crucial for the protection and performance of the timing chain, its gears and plastic guides all of which compose the timing chain kit. Car manufacturers always recommend that engine oil grades are tested and approved for the protection of engine components such as the timing chain kit, variable valve timing kit and all the other fast moving but sensitive metallic components.

Going forward, buy genuine a Toyota timing chain kit and have it replaced. Also ensure that the engine oil pick up strainer is free of debris and use the recommended fully synthetic 5W30 fully synthetic engine oil. This oil has higher performance and protection levels than the cheaper mineral grade oils and is designed to maintain viscosity, prevent corrosion, acid as well as metal sheer damage throughout the recommended drain intervals.

IS MY GEARBOX FAULTY?

Hello Paul, I own a VW Touareg which has been running fine until recently when it developed a rumbling knocking noise underneath. As I gain speed the noise lessens and is not noticeable. What could it be?

Hassan.

Hello Hassan, the rumbling noise underneath the car maybe caused by a damaged propeller shaft rubber coupler or mounting. It is a common failure at about 100,000kms. The propeller shaft, also called a drive shaft transmits torque from the transmission to the transfer transaxle to the wheels via the transaxle or drive shafts. The common cause of propeller shaft failure is fatigue or ageing of any of its components such as couplers, u joints or carrier bearings. Get the propeller shaft inspected in a garage setting to confirm the remote diagnosis.

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