Automotive → Re: Timing Belt? making screeching sound

If they timing belt was shot, it would slip, and at the little, it would cause mis-firing. At the most, it would cause the vehicle not to start. The idler pulley will cause a screeching noise, same if the spring where it meets the engine will screech when the vehicle is running.

We're talking serpentine belt here. The timing belt was recently changed. Read the ENTIRE thread.

What timing belt slips... do please tell us... they can JUMP teeth... but never seen one slip... big difference jumping teeth vs slipping... o and at most you could need a new motor... cause it goes bang.

also just because the t-belt was replaced does not mean any idlers were so that is a pointless argument... a new belt means a new belt... nothing more.

If the belt is not lose, the OP can put a drop of brake fluid on the belt and see if that stops the noise (I would still get it replaced at this age) just sayin.

And again, the idler pulley will cause the screeching noise, not the Serpentine Belt. Serpentine belts will screech when wet after driving through a puddle, but will stop after 30 sec's or so.

Contaminating teh belt with brake fluid will do nothing, but allow the belt to stretch & wear out quicker. Stop doing the shade tree mechanic stuff, and fix the problem is the solution.

Serpentine belts WILL screech when the rubber gets hard and brittle and looses it's grip on the pulleys. At that point, the belt has also probably stretched enough that the tensioner no longer holds proper tension. If the inside of the belt is cracked or shiny, replace it.

If the timing belt was replaced, the job if competent would have noticed that the Serpentine was shot and replaced after telling the car owner, or would have done it anyways at that age, especially putting the work into the car to replace the timing belt. If the belt is shot, and at the miles, replace the belt & idler pulley assembly. For a $130 dollars, you can get both and do it yourself, or have the shop do it for around $500.

If you are talking about the serpentine belt and idler pulley, your pricing is way off. They belt should be about $20 to $30 and the idler pulley $50 max. Add in an hour or so labor and it is more like $150 total.
Your assumption that the mechanic who replaced the timing belt would notice a defective serpentine belt also applies to the tensioner pulley on both the timing and serpentine belts. What ever the current issue is, it was not an issue when the timing belt was replaced. It is possible that a hack mechanic might replaced a timing belt, without inspecting it's tensioner pulley, but that is lost revenue and would expect the pulley to be replaced needlessly rather than ignored.
I vote for defective serpentine belt, especially since there is no indication that it has ever been replaced.