[mot88]

Squeeking sound at cold / morning start is quite common problem in Vios 1st generation (model code NCP42) and 2nd generation (model code: NCP 93). 

 

The cause is the fan belt / V belt . The original supplied by Toyota is Mitshuboshi brand (not to be mistaken as Mitsubishi). You may try other brand such as the long and trusted Bando or Dyco for a change. Years ago in Waja, the ori factory alternator  supplied is  Mitshuboshi  and it was the 1st that make squeeky sound compared to the other belts using Bando. Yes, Proton uses different brands for V belt from factory.

 

There is nothing special about using Original Toyota packing V belt (colloquial known as fan belt) as there are only a handful supplier for belt. For Japanese car, they either use Bando or Mitshuboshi as both are Japanese companies. I would prefer to use Bando rather than Mitshuboshi .

[vr2turbo]

Maybe need to tighten the belt a little more or just apply some belt grip. Normally belt make noise when the side gets glaze, or rubber has harden

[mot88]

There is some allowance for tightening but this is at the expense of giving extra load of the tensioner if the tension is already at optimal. Belt dressing is only a temporary solution and a can cost as much as the belt itself.

 

If one are going to owner is going to change the belt, there is alternative to try other brand rather than just sticking to ori Toyota which they sub-contracted to Mitshuboshi. 

[vr2turbo]

If belt already tight and still squeak then is time to change the belt already. Tightening only if belt is loose.....