This is probably a daft question, but can somebody explain why some cars have terrible brake sqeal whilst others don't. My hitherto faultless 2003 C5 is starting to develop a really annoying squeal on normal smooth braking from about 10 mph to rest, especially in hot weather. There's plenty of wear left on the pads and discs so the dealer's not prepared to do anything, even under guarantee. Comments...
It will probably be because the pad is allowed a little movement in the caliper and its this movement; that can be exagerated after braking in reverse; that causes the resonance and according squeal.
Should only need anti squeal compound (copper grease) applied on the sliding part of the caliper and the edges of the pad to cure it, unless its got real cheap quality pads fitted. Unlikely to be the back part where most compound gets put that is the problem.
Very surprised dealer not prepared to sort it for you; keep complaining, especially when he has new customers with him!
Check to see if the noise is coming from front or back. If it's the back, your calipers may well have corroded where they mate with the suspension arm, causing them to twist around and bring the edge of the caliper itself into contact with the disc. This is very common on C5s and Xantias. It can be fixed by unbolting the caliper, cleaning it down with an angle grinder and reassembling with copper grease between the alloy and steel mating surfaces.
On the other hand the back pads have maybe just seized. They don't get much usage - especially if the car is not heavily laden at the back. A good clean up and application of copper grease will again sort things out.
There are different types of lining available. I think Citroen introduced a type that is much improved. My C5 used to squeal a lot - but hasn't done it at all since a change of back pads about 3 years ago.
My C5 is also squealing with joy now that summer's arrived.
First port of call for me is always tyre pressures, as the self-levelling hydraulics can exaggerate the front-rear braking balance.
Second test is to load up the boot for a couple of days.
My Dad had a problem with one of the rear calipers siezing on his C5 - the rear brakes get very little use if there's no weight in the back. The specialist he uses freed it off and replaced the discs and pads and said he would fit Lucas parts because they don't squeal.
Its most likely that the noise is coming from the rear brakes, not the fronts. Your pads will be glazed over. Suggest you get some Lucas pads from GSF car parts and pop 'em in. Problem will be fixed. Citroen's standard pads are very hard and glaze over after about 15,000 miles.