Hello, my 2002 4S recently developed a sound at idle which increases in frequency as the rev's increase. I suspect it may be a failing idler pulley/water pump or the AOS. Any advice into troubleshooting would be greatly appreciated.

Failing AOS?

• There is a build up of oil on the intake plenum behind the throttle body but this could be due to an oil overfill that was driven for approx 10 min. (see pic attached).
• The vacuum created with the oil filler cap removed
• No smoke on startup or driving

However the pulsing sound seems to change with RPM and I am not sure if the sound of a failing AOS would be RPM dependent. I have read that I would need to test the crank case vacuum, however I do not have a spare oil filler cap to create my own tool to test.

Failing Idler Pulley/Water pump

• Sound RPM dependent
• No coolant that I can see yet dripping from the engine
• Probably original water pump @ 96000 km

I will be pulling the airbox and checking the pulleys this afternoon.

I have also linked 2 videos for reference to the sound.

• Idle with oil filler cap on
• Idle with oil filler cap off

Thank you in advance for your time

 

UPDATE: it was simply a 2" chunk of tread missing from the drive belt. I checked the pulleys and there was no excessive play or noises that would indicate bearing/water pump failure. Purchased a new belt and all appears well.