Mysterious But Very Loud Noise

[motherbruce]

Hi I have a 2008 Prius.

For some weeks now I have been getting a very loud squeal after about five minutes driving in slow congestion queues. Went to dealer last week and they couldn't find any problem (needless to say noise wasn't there on way to dealer that day!).

Now this morning schools are back, so are traffic jams and noise back with a vengence. So loud that everyone round about was looking and shaking their heads!

Is there an easy way to tell where the noise is coming from when you're moving in a queue? Louder when I open the window so outside but difficult to determine front or back, left or right.

Anyone any idea what it might be?

We are heading off for the bank holiday weekend so have booked in to another dealer on Thursday but was hoping for some guidance or reassurance before then!

Thank you

[capnbirdseye]

Is it one of your front wheels? when you get the noise pull up and touch each of your brake disks in turn, if one of them is hot & the others are cold then it's binding.

pads binding is a common fault on gen2, it's usually triggered on mine by doing a sudden stop from speed, & the pads seem to not retract properly when you move off. It's sometimes so loud that it makes passers by turn round to look :ffs: because the pads are binding it causes them to glaze over & they should be removed & the sheen removed with abrasive.

If it brake binding is then easily fixed on mine by reversing fairly fast ( rolling down a long slope is best) & then slam on your brakes, this should realign the pads,not had a problem for some time now.

but if it doesn't work then maybe it's a wheel bearing but if you already had it checked then I would guess 100% it's brake binding which won't show up easily at a garage check

[Burma Sauce]

Sounds like it's coming from a rotating part. As it's happened when you were parked in traffic I think we can assume it isn't road speed related. We have to narrow it down to another rotating part. This leaves us with:

• The engine - next time it happens go to the info screen and see if it shows the engine running
  
• The air conditioning pump - try turning the aircon off and see if the noise stops
  
• The transaxle cooling pump - no way of telling whether or not it's running from inside the car so try and rule out the others first!
  

Did it sound like a squealing fan belt? Yours could be on its way out. How many miles has your car done?

[motherbruce]

@capnbirdseye can't think of any sudden stop from speed this morning but thank you will try the braking solution, plenty of hills near me.

@Burma Sauce - it does sound like a squealing fan belt but only at 17,700 miles?

[Burma Sauce]

@Burma Sauce - it does sound like a squealing fan belt but only at 17,700 miles?

Worth having a look then - it doesn't actually drive the fan, it only goes round the crankshaft, water pump and an idler pulley. Give it a poke and see if it seems excessively loose. You're right though, shouldn’t be a problem at the mileage you've done.

[capnbirdseye]

@capnbirdseye can't think of any sudden stop from speed this morning but thank you will try the braking solution, plenty of hills near me.

@Burma Sauce - it does sound like a squealing fan belt but only at 17,700 miles?

Do the disk touch test after you have driven a while, just poke your finger thru the spokes of the wheels & onto the shiny part of the disk, if one is very hot then that's your culprit,

[acetip]

@capnbirdseye can't think of any sudden stop from speed this morning but thank you will try the braking solution, plenty of hills near me.

@Burma Sauce - it does sound like a squealing fan belt but only at 17,700 miles?

Do the disk touch test after you have driven a while, just poke your finger thru the spokes of the wheels & onto the shiny part of the disk, if one is very hot then that's your culprit,

if its hot, i hope his finger heals soon.

[capnbirdseye]

@capnbirdseye can't think of any sudden stop from speed this morning but thank you will try the braking solution, plenty of hills near me.

@Burma Sauce - it does sound like a squealing fan belt but only at 17,700 miles?

Do the disk touch test after you have driven a while, just poke your finger thru the spokes of the wheels & onto the shiny part of the disk, if one is very hot then that's your culprit,

if its hot, i hope his finger heals soon.

LOL, the point is tho you should usually find all four barely warm after a trip due to the unusual Prius method of regenerative braking, I'd put money down that it's the same problem as I had, the fact that it's been on the dealers ramp should have found such things as a slack belt or whatever but they'd likely miss a faulty disc pad clearance particularly if the vehicle went on the ramp after it had stood for a while. It is very loud when it occurs

[Grumpy Cabbie]

Are your brake discs rusty - esp the rear one?

If they are it sounds like you've glazed your pads. The only way to stop it now is to replace them and possibly the discs.

If it isn't this then I don't know.

[gaz9759]

Sounds like brake squeal, Copper slip the front pads and shims.

Also check that the backing plates are not touching the disc,s

[Mkuk0]

Not sure the Prius HAS a fan belt TBH! sounds more like binding brakes to me.

[Burma Sauce]

Not sure the Prius HAS a fan belt TBH! sounds more like binding brakes to me.

Not really a "fan" belt, but the 2008 Prius has a drive belt that connects crankshaft to water pump (and also goes round an idler pulley). The 3rd generation Prius has no belt.

[motherbruce]

This dealer says all 4 brake disks pitted and scored Going to have to break out the credit card. Thanks anyway guys so long as this fixes it I'll be happy.

[Opifex]

It's odd that the first dealer didn't spot this on Tuesday, especially as Grumpy managed to diagnose the problem without even seeing the car.

I have a light covering of rust on the rear discs so will occasionally be using the brakes a bit more fiercely to clean them up, and hopefully avoid your problem.

[capnbirdseye]

I dare say if your vehicle was under the dealers own warranty then it would magically not require 4 new disks & pads, I'd be very wary myself, do they really look that bad? The fact it squeaks is because the pads are rubbing on one of your disks as you drive along & making the disk hot & this alone should be all that needs sorting & not all four , probably only needs new pads on the front.

As I mentioned earlier I have the same problem from time to time & it started doing it again this morning in Asda car park, did a quick reverse & jabbed the brake (I checked behind first :censor: ) and all is well again

[Grumpy Cabbie]

Rusty, under used brakes is a regular item on the PriusChat USA forum.

Some recommend braking burning off the light rust every once in a while by driving down a hill in Neutral - so as to actually use the friction brakes and not the regen brakes. This isn't a personal recommendation but just a comment on what I'd heard as isn't coasting illegal or something? :!Removed!: