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'Whistling' from brakes

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whistling
4K views 45 replies 16 participants last post by  Topic 
#1 ·
Just started to get this on and off, usually at very slow speed, and disappears when I push the brake pedal.
Front pads and discs were changed about 10k miles ago.
What's causing the 'whistling' sound?
 
#3 ·
They still work perfectly, just 'whistle while they work' occasionally.
And not a squeak out of them for the previous 10k...

Something to do with freezing weather and moisture getting in there? Expansion/contraction?
 
#4 ·
my brake pads had also whistled and i changed it with 'ate brake pads', whistle problem solved but ate throws too much dust because of the soft structure. i know its terrible the whistle brakes and you feel everybody notices to the way the whistle comes:)


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#6 · (Edited)
Thanks OE.
Providing the braking efficiency remains excellent, I'll soldier on until I have to book it in for something else.
 
#8 ·
It'll be caused by the pads lightly rubbing against the discs, a condition known in the industry as "twitter" - some combinations of compound, caliper & vehicle do it, some don't, nothing to do with "hard" or "soft" pads. If it's only just started it suggests that the pads aren't moving freely any more, in which case cleaning the calipers will most probably cure it.
 
#9 ·
The seals on the calliper pistons are designed to 'recover' their shape which pulls the pistons back. They don't need the pads to create their own space. Obviously warped discs will push the pads back further (and create a soft pedal). New pads and discs together will create squealing if the pad rear surfaces don't have a coating. But whistling is caused by the pad material.
 
#12 ·
New pads and discs together will create squealing if the pad rear surfaces don't have a coating.
Not necessarily. During the development of a car the vehicle, brake & friction material manufacturers put in a lot of work to ensure acceptable brake performance, squeal being one aspect of this. Ideally there will be no squeal, or it can be developed out by modifications to some part of the system, but palliatives are often necessary - chamfering the pad, rubber coating the backplate, plastic or steel shims & so on. There's a greater risk, in theory, with aftermarket pads as they will not have been tested on every possible application.
 
#10 ·
Does the squeaking stop if you gently pull the handbrake up a little? If so, the noise is caused by the rear pads rubbing on the discs, and tends to be more prevalent when the brakes have warmed up. This is usually due the pads sticking in the carrier due to rust on the edges of the pad backing. If the pads still have plenty of life in them, they can be removed and cleaned up, with a little copper grease applied to the edges on re-assembly. This is a very common problem; I often have to "strip and clean" the rear brakes on cars in for service. Other potential problems are seized caliper slider pins, and sticking calipers, as well as defective handbrake cables (sticking and not releasing correctly).
 
#21 ·
I've done a fair amount of driving around today.
The whistling only starts when the car's fully warmed up. It does it at slow and fast speeds.
Pulling the handbrake up stops the whistling, but so does touching the brake pedal...
 
#11 ·
Thanks FoxtrotOscar :thumbup:
It stops when I touch the brake pedal so assume it's the front, but will have a go with the handbrake next time.
And as you have mentioned, it does only seem to happen when the brakes have warmed up.
I've had trouble with a sticking caliper before, but overcame that when I got the front discs & pads replaced.
 
#14 ·
For what it's worth, they are Mintex pads and Brembo discs.
So decent manufacturers I'd have thought.
 
#17 ·
:thumbup: All very informative chaps, it's certainly given me a better understanding of the world of brakes. Thanks.
 
#19 ·
Are you talking about whistling (which I've never heard of)
or squealing?

If it's squealing the try the previous suggestion of pulling the handbreak on a notch or two to see if that stops it.

If it does then you just need to remove the rear pads and clean the callipers with a wire brush, the dust from the worn pads seems to accumulate in the pad guides/runners and cause them to stick, I've done this on my last 159 and it cured the squealing no problem.

There were a lot of threads on here about it when I joined the forum 4 years ago.

If it's a whistling noise I have no idea, What tune is it whistling? :)

Axe.
 
#20 ·
Very much a whistling, quite a high pitched one at that.
Have had a 'squealing' on previous cars, this is different.
Bizarrely it's not done it today despite a lot of stop-start town driving.
But by God did it do it on Sunday, people in the house I was visiting heard me approaching from up the road.

Have had many things with Alfas over the years that have just come and gone, then sometimes come back again.
I'll see what tomorrow brings. And the day after...
 
#23 ·
How often do you use a handbrake???...
Whistle might come from rear brakes because pads are not quite free since handbrake cables rusty and jammed at their ends.
Just check the move of handbrakes cables from behind. If so ( sure it is ) you may put some WD-40 up there. It helps but not to long.
Normally you have to replace handbrake cables. It is really rubbish job.
In my climate handbrake cables life is 3-4 winters.
 
#26 ·
My brakes have been squealing since I got my car coming up to 2 years ago. 19" Ti brembo setup. Even after new pads, there was squealing when moderate pressure is applied, not too low, not too much. The discs are still the same as when I got the car, with plenty of life left. The pads have been chamfered twice after this, no real improvement. When I go in reverse and brake, I hear a big clunk from one of the pads and a extremely loud squeal then starts. When I brake going forward again, you hear the clunk as the pad slips back into place then goes back to normal squeal with moderate pressure. I have also done a full strip down including thorough clean of the pads and caliper, applied new ceramic grease, still no real improvement. It has to be the parts, I have Mintex pads which are new, unknown disc brand though.

While these Brembos are certainly effective, they are so noisy and sound a bit primitive.
 
#27 ·
At what sort of mileage do rear pads generally need replacing?
They obviously get a far easier time than the fronts.
They've never been touched in my 5.5 years of ownership, probably still on the originals at 48k.
Does that sound plausible?
 
#28 ·
I'd say that is possible.

The problem though is that the lack of wear brings on lack of maintenance and the caliper stops sliding properly and doesn't release the pad from the disc.

Old fashioned style maintenance would see the calipers striped down and cleaned at service time. With modern tick-box servicing, that doesn't happen.
Some garages do still put the extra effort in though, so not all services are equal.
 
#29 ·
Thanks David, much appreciated.
I'll get it looked at when it's in for other work.
 
#31 ·
Just had it in for a service today.
Rear pads and discs are fine.
What is on the way out is the off side front bottom wishbone rear bush.
A new arm is £88 on ebay and labour will be about £50. Hopefully this will solve it.
I'll get it ordered and booked in again at some point.
 
#33 ·
Without spending God knows how long on there, what's the conclusion? Suspension?
 
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