Mechanic & Drive Belt Repairs for Brompton

This page is about the accessory belt, sometimes called the serpentine belt. It is not the timing belt and the difference matters: the timing belt is inside the engine and its failure is catastrophic, while this one is on the outside and its failure is merely expensive and inconvenient.

On most modern cars a single belt snakes around the front of the engine driving the alternator, the power steering pump, the air conditioning compressor and, frequently, the water pump.

That consolidation is efficient and it means one failure takes everything with it. Lose the belt and you lose charging, steering assistance and, if the pump is belt driven, cooling. The car will stop shortly afterwards, and if the water pump went with it, the engine may overheat before you notice.

Any mechanic Brompton drivers use should be inspecting this belt at every service, because unlike the timing belt it is visible and takes thirty seconds to check.

• Cracks across the ribs, which is normal in small numbers and a warning in quantity
• Glazing, a shiny hard surface that slips and squeals
• Missing chunks out of the rib edges, which means the belt is misaligned
• Fraying at the edges, usually a sign a pulley is not sitting square

The belt is held tight by a spring-loaded tensioner. As that spring weakens the belt slips, and slipping causes the squeal most people associate with a worn belt.

Replacing the belt without checking the tensioner is one of the more common ways a squeal comes straight back. So is ignoring the idler pulleys, whose bearings wear and produce a rumble that changes with engine speed and is often mistaken for something inside the engine.

Very common, usually harmless, and worth understanding. Overnight moisture on a slightly glazed belt reduces grip, so it slips for a few seconds until it dries and warms.

If it only happens cold and clears quickly, the belt is ageing. If it squeals when you turn the wheel or switch on the air conditioning, the tensioner is no longer holding it properly and that is worth booking in for.

2/208 Grange Rd, Flinders Park, four minutes from Brompton. A mechanic Brompton drivers use should be looking at this belt at every service.

Call (08) 8443 7900.

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