Ask the Mechanic

WHY DOES MY TIMING BELT BREAK FREQUENTLY?

Hello Paul, I drive a Toyota Vista Ardeo 1999 model. Of late, my timing belt is prone to breaking. What could be the cause? Also, when I start the car after it being parked for some time, the engine makes a strange sound. Could my oil pump be damaged?

Mathias

Hello Mathias, a timing belt (T Belt) helps to connect and synchronise the engine crankshaft and camshafts to ensure that the pistons and valves in the engine do not collide during combustion cycle. Therefore, the timing belt works hard and plays an important engine protective role. In most cars such as your Toyota, the T belt is given a lifespan of 100,000kms by the manufacturer.

Heat and friction in the engine wear out the timing belt rubber material overtime. The worn out T belt rubber teeth fail to grip the timing gears. As a result, the timing belt slips, which causes expensive damage to valves and pistons. A new T belt may repeatedly fail prematurely because of low oil pressure, leakage of engine oil on the timing belt, misalignment of shafts and timing pulleys, under tensioning of the T belt, worn out timing pulleys and intrusion of dirt, oil and grease.

Low oil pressure affects some timing belt tensioners, which can lead to belt slackening and disengagement from the pulleys. Low oil pressure could affect the running of camshafts, which would lead to T belt snapping.

Leakage of engine oil from worn out crank shaft seals will damage the T Belt and cause slippage from the pulley.

Misalignment of shafts and timing pulleys during assembly or fitting will cause uneven T Belt tooth wear, cracking or tear. Correct alignment of these components will contribute to a longer T Belt lifespan.

Under tensioning of the T Belt belt during installation when you reuse a worn out belt tensioner will cause T Belt skipping, uneven wear and premature failure. Consider replacing the tensioner during T Belt renewal.

Worn out timing pulleys with bad teeth will cut or sheer the T Belt soon after installation. Consider replacing the T Belt pulleys during T Belt replacement.

Debris, oil and grease in the timing belt pulleys can weaken and damage the belt rubber material.

For the strange sound in your engine during cold engine starts, get a mechanic to inspect the engine oil pressure during cold starts. It could be an oil pump failure due to accumulation of sludge and dirt in the engine oil sump. This clogs the oil strainer on the oil pick up tube, hence delaying delivery of engine oil to fast moving metallic components in the upper part of the engine. Accessing the oil pick up tube in the sump will confirm this problem. To avoid this, use reputable engine oil with the correct viscosity and blended with detergent additives to combat dirt and sludge buildup in your engine.

CAN WRONG USE OF THE HAND BRAKE DAMAGE THE GEARBOX?

Hello Paul, there is an article doing rounds on social media which claim that wrong use of the hand brake and pattern of shifting from drive to parking can damage the automatic gearbox. Is this true? Kamoga

Hello Kamoga, it is generally true that the automatic gearbox can be damaged by wrong use of the hand (parking) brake and pattern of shifting from Drive to Parking. This is especially if the car is parked up or downhill. On a straight level ground, it may not matter much.

The automatic transmission can be damaged when you shift from parking to drive after disengaging the handbrake (parking brake). Damage happens because the weight of the car is resting on the transmission. The best thing to do is use the foot brake as you shift to neutral and engage the parking brake before shifting to P (Parking) This way, the weight of the car will rest on the hand brake (parking brake).

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