Can't stop drivebelt squeal.

[dsmith1974]

Hi,

Our T25 1.9 WBX has a single drivebelt (altenator, water) that I tried to tighten today (by hand and a little spanner leverage). The deflections about 15 maybe a little more with a reasonable (not rock hard) push of the thumb.

It's as tight as I can get it, but the squeals still there.

The belt looks OK (no frays or cracks).

Should I try a new belt next anyway?

Thanks,
Duncan

[itchyfeet]

Probably needs to be a bit tighter then
also check for coolant or oil contamination of the pulley
are you releasing and retightening the lower hinge bolt?
also check the alternator lower mount is securely fixed to engine, have heard of stripped studs so alternator moves

[kevtherev]

got a picture of both sides of the belt. ?
If as itchy says, your pulleys are out of whack it will squeal

and it needs to be tighter

[CovKid]

Bet its not the drivebelt thats squealing.......

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It'll be your waterpump about to pack up. Do read that first - before it does go. Tightening the drivebelt works for a while because you're actually putting tension on the squealing waterpump bearings. Eventually bearings get so bad, tightening the belt no longer works.

[itchyfeet]

A good point, drivebelt squeal usually happens only just after startup when the alternator is working hard to recharge, if its permanent them maybe pump.

[dsmith1974]

I could believe it to be the pump, it does all smell a bit hot. Sounds like a nasty job with all the seized bolts. I think I managed to strip the lower alternator hinge thread when trying to undo the bolt already today.

If an impact driver is for applying torque without damaging screw heads by cam out. Is an impact wrench a similar device for working loose seized bolts. I applied some penetrating oil, waited 5 mins and gave it a tap with a hammer before trying to undo it with a box spanner. Should I have used an impact wrench instead?

How come the belt is more likely to squeal when the alternator is under load (after starting)? I figured it's the belt that drives the alternator, that generates whatever electricity it can by moving a coil through an excited electromagnet. Just because the battery may be more hungry after turning the engine over, doesn't mean it can influence the belt to move any quicker than the crank pulley, does it?

[dsmith1974]

By impact wrench, I think I meant like a manual impact driver but with a socket attached (not like an air gun).

The real question is, how best to remove a seized bolt??

[itchyfeet]

Leave the hinge bolt for now if possible, loosen the belt and remove it and check if the pump spins freely and see what play there is in bearings
also check same for alternator.

alternators take more effort to rotate the more power they have to make so when recharging a battery after starting the belt is more likely to slip for a short while.

lower hinge bolt did you just round the nut corners or is the nut spinning on the bolt?

[dsmith1974]

So if the battery's drawing more current then the physical resistance will be higher. Makes sense. I hadn't thought of that.

The corners are fine. Not rounded. But the bolt just turns and turns, neither comes out nor tightens.

[CJH]

That lower bolt is a nut and bolt. My apologies if you knew that, but I mention it in case you haven't seen the nut, and without a spanner on the nut it'll obviously just turn.

[itchyfeet]

Yes an alternator can't make power from nothing, the engine and belt has to work harder to turn it when it it's generating more power.

You probably need to cut the head or nut off the bolt
you will strugle to get in there but you can remove the alrernator with the lower bracket but there is a risk the studs to the engine strip or break then you have bigger problems, try penetrating oil and see if they move

but also see if you can move the alternator with the hinge bolt as is, if so you can do that later, take the belt off as described above andcheck pump and alternator.

[itchyfeet]

That lower bolt is a nut and bolt. My apologies if you knew that, but I mention it in case you haven't seen the nut, and without a spanner on the nut it'll obviously just turn.

never thought of that easy mistake to make

[Reimotim]

How old is the belt?
Is it the correct size?
Worth a check, sometimes people or recovery companies will fit the incorrect size as a "get you home" measure. They tend to work for a short while, but inevitably start to slip.


Tim

[CJH]

also check the alternator lower mount is securely fixed to engine, have heard of stripped studs so alternator moves

Mine had this, and it did cause a squealing belt. It also introduced an extra vibration/wobble which I could feel through the gearstick at times.

[silverbullet]

Of course it could always be that the alternator bearings have gone dry...