2018 Chevrolet Sonic Timing Belt Idler Pulley Replacement Cost in Seattle, WA

The idler pulley is bolted through the center into the engine, and the smooth side of the timing belt turns the pulley to reduce friction and heat.

If the idler pulley fails, there will be a very audible chirping noise from the front of the engine. This is because the idler pulley bearing is no longer smooth. If it is not changed immediately, the engine will being running roughly, or stall completely, and internal engine damage may occur due to slippage or breakage of the timing belt. The check engine light will illuminate on the dashboard in the event of total failure, and OBD trouble codes for misfires, crankshaft position, and camshaft position will be stored.

It is not recommended to drive a vehicle suspected of idler pulley bearing failure. This can quickly result in complete engine failure as described above.

Timing belt idler pulleys are replaced during a timing belt replacement service, either as preventive maintenance or due to suspected failure. This means the average idler pulley replacement occurs between 60,000 and 105,000 miles, depending on the manufacturer specified timing belt service interval.

Diagnosis of a failed or failing idler pulley requires removal of many components, and hands on inspection of the idler pulley. If the servicing technician finds the pulley is loose or damaged in any way, they will recommend immediate replacement of, at minimum, the timing belt and idler pulley.

At a minimum, replacement involves removal of the timing cover, timing belt tensioner, timing belt, and, finally the timing belt pulley. When this service is performed, it is common to replace the timing belt, water pump, and seals. Once all components are replaced, the timing components can be installed onto the engine, and the engine will be tested for proper operation and timing.

Since this service requires removal of the timing belt, it is recommended to replace the timing belt, water pump, and possibly front seals at the same time, unless they have been recently serviced. This is much more cost effective than returning for the same service after a partial service interval has elapsed.

Some engines use more than one timing belt idler pulley, which affects the cost of the repair slightly. The pulley can fail at random, especially if debris is pinched between the timing belt and the idler pulley. It may be necessary for the motor mounts to be removed from the vehicle, as well as engine cooling fans, the radiator, and all engine accessories.

Since timing belt idler pulley replacement necessitates the removal of timing components, it is not recommended for the DIYer to attempt this task. A thorough knowledge of internal engine components, engine timing, and several specialty tools are required to properly perform this repair.