Grinding & squealing Xantia brakes

TBONE · Post by **TBONE** » 27 Oct 2008, 17:51

so your sure you turned the piston all the way back in? is it sticking and did you have to force the pads in (even slightly)? are the dust covers well away from the discs ( they make a nasty squeal and grind when jammed on the disc ) did you set the handbrake up how many clicks??,
I know most answers will be yes I done that but its just to point out what you might have missed

handyman · Post by **handyman** » 28 Oct 2008, 15:10

This has been a topic in the past so a quick search of the archive will throw up the information.

The handbrake cable outer covers are prone to splits which lets in water, of which there is copious amounts around the front wheels. Dirt follows the water into the cables and lo and behold the cables jam or never free off properly.

This causes the pads to be pulled onto the discs just enough to heat up and cause the squealing.

When changing pads, it is always a good idea to disconnect the cables, slip them out of the calipers, lubricate the ends and ensure the inners are sliding freely. Any splits in the outer cables can be taped up with self-amalgamating tape, ensuring a longer life for the brake cable.

If you have trouble sourcing self-amalgamating tape, PM me. I use some ex-MOD stuff designed for tanks.

Never force the pads back into the calipers, as you will cause the threads on the handbrake self adjusters to strip. ALWAYS wind the caliper pistons right back into the caliper.

Handyman

Stunned Monkey · Post by **Stunned Monkey** » 29 Oct 2008, 17:30

My car has had this issue from only 6 months old and went back to Citroen under warranty around 5 times, in the end with me behind the wheel taking their service manager for a 100 mile round trip till the blasted thing made the noise. They never did work it out. It's a kind of thrummy humming noise which can occur at all speeds from 5mph to 90mph. It's very different from normal squealing. The car was too "new" to need handbrake cables (it does now though!) but there's one thing I know for certain... the noise goes away with new discs and pads, and only occurs if new pads are put onto even partially worn discs. It has something to do with the way the new pad gets worn between existing lips on the discs. If you chamfer (sp?) off the edge of the new pads, it may stop, but new discs and pads have always worked for me. I do new discs to every two sets of pads and I'm in the "put up with it" phase right now

handyman · Post by **handyman** » 30 Oct 2008, 09:26

Hi Martin, sounds like you have the effects of the phenomena "Sympathetic Resonance", which is when the dynamics of moving parts are coupled together to create a harmonic. You are obviously affected by this harmonic which may well be something related to the drive train, like a driveshaft very slightly out of balance or a series of dynamics like a shaft, brake disc and wheel, which when coupled together create the sound you can hear.

The problem may not be exactly where you think, but may be elsewhere in the car. Sometimes, the resonance can be heard in panels which may need realignment or added sound deadening to damp out the harmonic.

You need to have a good listen to where the noise is coming from.

Handyman

Stunned Monkey · Post by **Stunned Monkey** » 30 Oct 2008, 16:25

Trust me on this, it's definitely the brakes! A little tug of the handbrake while moving and it gives a little "chirp" and shuts up. You can feel the vibration through the handbrake lever and the brake pedal until pressed. Plus as stated, it only happens with new pads on old discs, and has done so consistently over the 3 or 4 sets of discs that I've gone thorugh.

Xaccers · Post by **Xaccers** » 30 Oct 2008, 17:25

Stunned Monkey wrote:it only happens with new pads on old discs, and has done so consistently over the 3 or 4 sets of discs that I've gone thorugh.

If the new pads don't fit the old channel in the discs that the old pads made, then they'll make a noise as they won't fit flush with the surface of the disc.

Jenny's got this problem (although her pads and discs have life in them) because someone used a big split pin to retain the swing bit of the caliper on one side rather than the proper pin.
Now it's got the proper pin, the pads are held further in, and so don't fit the trough they have made.
Makes a hell of a racket when I brake!
So will be replacing her pads and discs when I do her strut tops.

handyman · Post by **handyman** » 30 Oct 2008, 21:02

Hello Martin, if you can feel the vibration through the pedal, you have something seriously out of alignment. Has anybody put a clock gauge on the discs, hubs, etc. to check for run-out?

When I got my first Xantia estate, I had this problem, which turned out to be radial cracks in one of the front discs. It was still within wear limits but was obviously failing.

Have you checked the rear discs on the car?

Handyman

Stunned Monkey · Post by **Stunned Monkey** » 30 Oct 2008, 22:09

Thanks for the thoughts guys, but I do know what I'm doing - I've had my own workshop for the past 5 years. I specialise in a different car but do all my own maintenance on the Xantia. I've had the Xantia for 8 years and 180,000 miles, and the brakes first made the noise when I was driving home from the dealer at 21k miles and 6 months old.

To reiterate - it's not "normal" squealing but a very specific note that is low enough that you can hum it and is the same regardless of speed. Aside the fact that I know it's the brakes, it wouldn't do it at 5mph if it were a balance issue. It is caused by new pads on old discs.

New pads on old discs take longer to bed in but efficiency is fine - doing 80 miles a day at the moment and have been for the past month. The pads are now 3 weeks old and braking is as good as it ever was/is (excellent). Not quite up to the standard of the Venturi though!