Do you need to retighten a new serpentine belt? Toyota yaris 07

the car required a new water pump, the mechanic suggested to also replace
the serpentine belt because of age -
after a week the car made high pitch noise when started, the noise stopped after the initial start-
at the shop it was explained that a new serpentine belt requires tightening after the car has been
driven for a while - like a week-

is this correct or was the belt not installed correctly

the year of the car 2009

I had the timing belt replaced on my wife’s 06 Sienna last June. The serpentine and PS belts were also replaced. The serpentine belt has a tensioner pulley, but the PS belt is tightened by hand. On the way back from the shop the PS belt started screeching loudly.

I took it back to the shop to have it checked. The shop explained they prefer not to over-tighten the PS belt on installation. The belt tension was readjusted and there have been no further issues to date. Your shop’s explanation sounds reasonable.

PS = Power Steering, on the Sienna the noise would stop once the van had been driven for a few minutes. My guess is the belt warms up and had better grip. The noise did not reoccur after the belt was

Personally, I’m happy the mechanic erred on the side of caution with the belt tension. Returning to the shop was only a minor inconvenience.

Ed B.

thanks for the comment-
what is a PS belt?
why is there noise only at every start and then disappears?

well - i hope that i hear no more noise now -

PS = power steering.

the mechanic should have advised about coming back for re- tightening

my first reaction was: another bad repair

had too many bad experiences with garages, wasted time, wasted money -
no good consumer laws whatsoever -

A squealing belt is slipping. A slipping belt is heating up. A belt that is heating up is shrinking. A belt that is shrinking stops squealing. There can also be an effect of drying moisture off the belt which stops the squealing.

The belt was never tight enough. The belt on the Yaris is known for squealing if it is not tight enough. this has been a common issue for a long time and there was a T.S.B. just issued for it, T-SB-0012-15. The belt has to be tighter than what most techs expect. I would install a new belt and tighten it correctly.


i could not find the technical service bulletin 0012-15, and does it concern the yaris? if yes
can you post the link?
also i wonder now if the belt was just making the noise instead of the waterpump?

I’ve been guilty of erroring on the side of not over-tightening belts, because I worry about stressing the alternator bearings. It has resulted in having to re-tighten some of them.

why is there noise only at every start and then disappears?

Isn’t that because of the short term higher load on the alternator after you start the car to replenish the drain from the starter ?

I can’t post the bulletin, but what it says is the belt should have less than .035 deflection. Your shop should be able to look up the TSB

Just get the belt tightened. Unlike most serpentine belts, which have a spring-loaded idler pulley (and therefore don’t need re-tightening), the Yaris is tightened manually with the alternator. Here’s a video showing the replacement process: