Under Bonnet "bag Of Nails" Noise

[Catlover]

Yaris T-Spirit 1.4D 59 plate, 50k miles. The car starts well, performs very well, accelerates as always, no loss of power etc, and still getting 62.2mpg according to the computer.

Few weeks ago the under bonnet noise at tickover and lower revs sounds like a bag of nails. Makes no difference if clutch depressed or not.

When I lift the bonnet, its coming from the driver side (RH drive), and further listening brings me to the front of the engine.

My thoughts (which could be wrong) - Could it be the alternator? and if so what? and is it repairable? and is it worth it? or is a new one more cost effective?.

[bathtub tom]

I'm not familiar with your engine, but modern alternator pulleys usually have a 'clutch' device to smooth out shock loads. Could also be A/C compressor clutch, or crankshaft pulley damper (if it's got one).

I'd slacken or remove the drive belt to help diagnose the source. You could 'waggle' the relevant pulleys while the belt's off to see if there's any looseness.

[Catlover]

Thanks for those thoughts Bob

Anymore comments, perhaps from the experienced Yaris/Toyota owners?

[Madasafish]

1. The weather is colder.

2. When was it last serviced?

3. Could be anything from timing chain, to lack of oil, to injectors etc

4. When was the fuel filter changed?

[Catlover]

All sorted.

Took it to my local garage (non Toyota) just round the corner. He listened and said its the water pump (which sits just below the alternator-my thought).

Left it with him this morning and just collected. Lovely and quiet again. Water pump with 3 year warranty fitted.