Saxo Problem

Little problem with my Saxo that I'm after some help with. It's 1.1 Desire, coming up to three years old with 51K on the clock. When I'm driving a long I keep intermittently hearing a constant squeaking noise coming from the front passenger side wheel, which stops when I apply the brake and then starts again when I take the brake off. I had the car serviced last week (not at a Citroen dealer - too expensive) but it was a major service including brake fluid change and brakes cleaned, they weren't able to find the cause of the noise and they didn't hear it themselves. The brakes are fine as they were checked on the service and cleaned. The wheel has been changed due to a flat and it still does it. I've noticed that it doesn't do it until I've driven about 10 miles then it starts.

Anyone any ideas what could be causing it?

Reply to
Mr No Spam
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Someone forgot to put coppaslip on the back of the pads.

Irratating, but not a problem.

Reply to
SteveH

I have experienced similar noises when brake and other dust builds up in the brake calipers and the garage don't clean them out on servicing. The brake pads then become partly seized so that they still apply normally but don't release fully. If that is the case the brake and thus the wheel on that side will become significantly warmer than the other.

If you find that is the case, you need to clean them or get them cleaned before the problem gets worse. I speak from experience. :-(

Roger

Reply to
Roger H. Bennett

Most likely the noise is the pads rubbing gently on the disks due to them not fully releasing and nothing to worry about. The disks are not perfectly true and the small amount of run out is supposed to push the pads away and provide a small amount of clearance. For what ever reason (sticky pistons?) they are not clearing and rubbing slightly against the disk. A new set of pads would likely solve it completely.

If it bothers you, then take it back to the garage and tell them you are not satisfied with the result of their service work.

Reply to
Harry Bloomfield

What complete and utter bullshit!

Reply to
SimonJ

I've had exactly the same problem on my car since I replaced my pads and discs. It's mainly when I steer right slightly. I'm hoping that it'll go when my brakes have bedded in.

Reply to
Peter

SimonJ submitted this idea :

Then I suggest you read up a little on the theory of disk brakes.

Reply to
Harry Bloomfield

Harry is perfectly right on this one - this is why disc brakes have no pull-off springs, the natural movement coupled with the release of pressure and a bit of pull from the seals moves the pads away just a tiny fraction, so there is no real "slack" to take up when you press the pedal, but at the same time no "brake binding" effect either.

See

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Drum shoes of course do have some way to move, and the tendency for the leading edge to pull onto the drum as it spins helps create the need for pull-off springs. You simply do not get that kind of effect on normal discs.

Reply to
R. Murphy

Did you replace the anti-squeal shims or coat them with brake grease or copper-slip when you put the new pads in?

OP: Are these the original pads? I don't know about Saxos but on the Rover 214 I had and a friend's Civic (basically the same car and uses the same front brakes) there is a metal bracket riveted on to one pad each side that touches the disk when there is ~3mm material left. The idea is that it causes a squeak to alert you that the pads need changing (cheaper than a warning light I guess). In the handbook for my Saab 9-3 it says that the brakes (are designed to) squeak when the pads need changing - I haven't looked at the brakes on this, but I guess it uses a similar "mechanism".

Also, on both my Rover and my friend's Civic, when I changed the pads there was 3-4mm more material on one side (i.e. one wheel, not one side of the same disk) than the other. The pads with more material on could be pulled out by hand, the other side required a hammer to remove them from the carrier so it could be the pads sticking in the carrier/caliper causing them not to release properly.

Parish

Reply to
Parish

So these pull-off springs are similar to Piston Return springs then. Which obviously a Wankel engine doesn't need, just like disc brakes don't need pull-off springs.

Interesting, thanks. .

Reply to
PC Paul

The message from "R. Murphy" contains these words:

If that were true then if you had the wheel up and not turning, it'd be held quite tightly when you released the brakes - which it clearly isn't. In most cases, except, tellingly, when you have a stuck piston, the disc is free to turn. You can even slip a thin feeler blade between the pad and the discs.

The springyness of the seals seems to be more than enough, without having to have any run out on the discs.

Reply to
Guy King

Thermal movement of the components will aid it as well. If the disks were machined slightly out of true then it would have to be such a small amount to prevent judder that they would wear down to true quite quickly thus negating the effect.

Parish

Reply to
Parish

No, he is totally wrong. Many cars with properly fitted discs, have very little, or no runout. If Harry's theory was correct, then these cars would have binding brakes. Also if it was the runout that gave you the running clearance, then the pads would only have clearance on part of the revolution of the wheel, and would rub on the high spot all the time. The hysteresis of the seals pulls the pistons back a fraction, thus giving running clearance, nothing whatsoever to do with runout.

Reply to
SimonJ

Yeah, we definately put some copper grease somewhere, must've been in the right place. The brakes seemed OK today, maybe it's going as they bed in?

Reply to
Peter

Nope, but you do tend to have a pedal return spring, and hydaulics. The pedal springs back and draws the piston back in. And "run out" within specs, does move the pads back, but if it goes out of spec, it can lead to the need to pump the pedals, similar to air in the system, first the first brake use as the pad position resets with each use.

Reply to
Sleeker GT Phwoar

The message from Sleeker GT Phwoar contains these words:

How - the pedal pushes on the piston through a rod, which isn't attached the the piston - it only rests inside it.

Reply to
Guy King

Sleeker GT Phwoar formulated the question :

I am not sure whether you are arguing for or against the way I suggested the pad clearance is achieved...

The spring only lifts the pedal back up. The pedal operates a push rod going into the master cylinder. It is not attached to the cylinder it can only push on the piston, not pull it back.

Reply to
Harry Bloomfield

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