The idler pulley is a component that doesn’t power anything but it makes sure that things can be powered correctly. Your drive belts power things like power steering, alternators, water pumps etc. The idler pulley makes sure that all of these can be powered as they should and that all the required belts stay where they should.

What is an idler pulley? 

It is a spinning wheel attached to the engine and inline with the belts that it is keeping in line. It’s made out of a plastic, rubber or metal material wrapped around a bearing that is fitted to the engine. It often has small uplifts on the outsides of the wheel to stop belts slipping off. 

Why do you need an idler pulley?

As your drive belt weaves its way around all the accessories that it powers, it needs to be tensioned and held in shape. The tensioner takes care of the tensioning and the idler pulley marks sure that the belts hold their shape. Without it, you may find your accessories underdriven and not working as they should. Worse still, your belts may slip off of their pulleys and that can lead a real engine disaster.

How to tell if you need a new idler pulley?

If your battery is going flat but your alternator isn’t to blame, if you hear a squealing from the engine while it’s running, the car often overheats, power steering is harder to turn than usual, or your belts are excessively worn or slack. 

How is an idler pulley replaced?

All engine coverings and components in the way of the belts are removed to gain access to the belt assembly. The tensioner is loosened and the belts removed. The idler is then inspected as well as the other pulleys and belts. The idler will then be unbolted and the new one bolted on. The belts will be refitted to the pulleys and the tensioner will be reset to tighten the belts. The engine will then be run and checked before all coverings are refitted.

How much does an idler pulley cost?

It can be as cheap as $50 and over $400 for multiple replacements. Bear in mind that often if the idler or tensioner needs replacing, the belts will need to be replaced as well.

How often do I need an idler pulley replaced?

Only as often as they fail, they can often last over 200,000km and sometimes fail inside 50,000km. It all depends on how long the inner bearing lasts.

Is a broken idler pulley unsafe?

It can be if it causes the belts to fall off while you’re driving. This can lead to a loss of power steering, cooling, braking, electricity etc etc. If it starts playing up then it’s a good thing to get fixed as soon as possible.

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