Yesterday an unusual noise slowly started seemingly from the front N/side wheel on my 98 Vectra diesel. Difficult to describe but like a low frequency brake squeal.
Gradually got worse and was there intermittently particularly at slow speed when not using the brakes.
Arrived home and removed the wheel trims and found the hub cap very hot on the O/side (not where the noise was coming from).
Today removed the wheels and found the disk retaining screw N/side had come very loose and the disk could be moved quite a bit backwards and forwards.
No signs of it fretting on the back of the road wheel, but tightened it up not really thinking it would cure the noise as the wheel bolts would have secured the disk when the wheel was replaced.
But the noise seems to have gone on a short road test.
However coming back to the O/side the outer pad is much more worn than any of the other three. Resistance more plainly felt when turning the wheel by hand.
Any ideas why the pad should be more worn and perhaps a theory as to why the disk screw could (hopefully) have been making the noise.
wemyss
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The wear on the outer pad sounds like the caliper isn't sliding properly. Cleaning and checking these caliper slides is where I would begin. I would also be tempted to fit new pads if they have been severely overheated - just for peace of mind.
As far as the squeal goes, it's easy to believe that tightening the screw could change the noise - brake squeal is really difficult to predict. For example, just stripping and re-building a disc brake can either cure, or bring on a squeal even if no parts are renewed.
Number_Cruncher
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Aren't these retaining screws supposed to be put in with Loctite? Is it possible that loctite wasn't used the last time the discs were changed?
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If it is a disc retaining screw it wont matter if its in or out, the discs wont go anywhere once the wheel is on and they are fastened a lot tighter than any retaining screw. Difficult to see how it could come out anyway with the wheel against it !
Sounds like a sticking caliper is causing the pad problem; needs investigating and curing. Quite possible if a pad was binding it would have been causing the squeal; just your ears telling you the noise was from opposite wheel.
Tracing noises is notorious for thinking its coming from somewhere its not !
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Thanks for your replies.
The pads or disks have never been renewed. have had this car from new and the mileage is still only 37500. (The wifes car gets all the use as its the first in the drive).
The other pads are virtually unworn,
The screw on the O/side had a dash of yellow paint on it. The one which was loose hadn't.
Even so the yellow paint one tightened a little.
"Cleaning and checking these caliper slides is where I would begin."
Would you describe the method..I'm pretty useful with tools but would like a little expert knowledge before I begin.
wemyss
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The calipers will have only one piston, which acts directly on the inner pad. The body of the caliper then slides, and applies force to the outer pad.
Typically, there will be some type of clip around the outer pad to remove.
Then, you need to remove the two bolts which also act as the caliper slides. These will be found under plastic caps. With the caliper off, you can;
1) Retract the piston - using whichever of the various methods you see fit to choose - many here advocate opening the bleed screw, and clamping the flexi first to avoid pushing murky fluid back through the ABS or potentially flipping the master cylinder seals.
2) Check that the brake pads can move smoothly against their supports in the fixed part of the caliper which remains fixed to the hub. Sometimes, if you fit new pads, they have rough edges which can cause them to stick. A few minutes with a file can deal with this problem.
3) Clean and check the caliper slide bolts themselves. If you find copperslip on the caliper slides, it is possible that the rubber has swelled, and the caliper may no longer slide. In this case, see if you can get hold of new slide rubbers, and iff the chrome is coming off the slide bolts and being replaced by rust, new ones of those.
4) If your pads are so old, and have overheated, I would be tempted to fit some new ones. See what the pad material looks like.
5) Check both sides of the disc surface - sometimes you can't see much of the inner face until you hve the pads out.
A Haynes manual will have more detail about tightening torques, etc.
Number_Cruncher
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Then you need to remove the two bolts which also act as the caliper slides. These will be found under plastic caps.
Assuming we are taking about the front brakes. I changed the pads on my 98 2ltr Vectra recently, once you get the plastic caps off you will need a hex socket or a big allen key. Can't remember what size. I remember being annoyed as I was expecting a normal bolt and only had normal sockets on me.
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you will need a hex socket or a big allen key. Can't remember what size.
7mm.
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Thanks for the advice. Job done and the chrome pins you mentioned NC had just a little bit of sticky rubber at one as you mentioned and cleaned off with with white spirit. The pads took quite a bit of filing to fit and move smoothly.
The test will come with a long run but it seems to be more free when spinning the wheel than before. The pads appeared Ok so didnt replace but will check again in a short while.
Yorkie the disk retaining screw was halfway out and could have probably come out all the way.
The inside of the steel wheel has raised parts where the bolts pass through leaving perhaps half an inch or more either side for the screw to come out.
I'm pretty sure this was causing the noise. Perhaps through some kind of resonance but as NC mentioned its hard to pinpoint what is causing it.
Thanks again to all.
wemyss
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Thinking on....The loose screw would most likely have come up agains the steel rim when halfway out and was jingling against it.
wemyss
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As one of the long-standing problems of automotive engineering, disc brake squeal must rank as one of the more tricky. Work has been ongoing in various university departments for many years, and manufacturers are still approaching universities to do more work on the subject. I've seen theoretical and rig based experimental work and combinations of the two - I've read a number of Phd theses on the subject, and there aren't many firm conclusions to be had.
However annoying, one thing that is reassuring is that in many cases a squealing brake does not necessarily or generally mean an inefficient brake - obviously, if it's squealing because there's no friction material left, that's not true!
Number_Cruncher
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