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Discussion Starter · #1 ·
Hi all
I have an ineffective rear offside brake - I have replaced pads and caliper, but still have a soft pedal and disc that is not wearing clean (ie not shiny in the slightest).
I thought the caliper was at fault, but have been advised that it could be the brake compensator valve mounted on the rear axle. I have looked through my Haynes manual and can find no mention of this.
Can anyone help me with this?
Thanks, as always
 

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There is no brake compensator on a 9-3. It was only used on the early 900's. The rear calipers on these cars can be problematic with the issues you describe. The piston seizes in the bore due to corrosion. If it's minor you can pull the dust covers, scrape away the rust and lube the bores with some red piston grease but if it's bad as your sound you may be better off sourcing some rebuilt calipers or a good pair of S/H ones.
 

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Discussion Starter · #3 ·
Thanks Shirozina, I did wonder as much. From major problems earlier in the year, I thought the hydraulic brake lines ran uninterrupted from the abs module to each caliper.
I tried clamping the flexi hose at the problem caliper, and I then got a solid pedal.

Is there a way to check if a caliper works whilst it is not on the car?

Any help greatly appreciated.

Kind regards
 

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The way I tested them was on the car by removing the pads and then seeing if you can lever the pistons back without too much force. If they move back they are not seized but a ridge of corrosion may have built up to limit their travel so I then pulled off the boots to look at the cylinder wall ( I had removed the disks). If it's not too bad it can be cleaned up and some red grease will restore the action but all too often the piston gets seized in the bore and it's very difficult to fix it. New / recon calipers do come up on ebay as they are a standard GM part.
 

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Have you check the flexi pipe to that calliper? Sometimes if the pipe has failed internally the pipe will bulge under pressure resulting in similar symptoms to what you have.
 

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Discussion Starter · #6 ·
Shirozina - will have a look at the caliper whilst mounted on the car (although I have a spare in the shed, so I will clean and lube that too). I think I may have a problem removing the disc, as the retaining bolt's head/spline slot has been rounded -- but i'll have a go.
Markwoodruff - it had new flexis all round earlier in the year, so they ought to be fine. But I will double check - just in case!

Am i right in thinking that, if the disc is removed (and the car safely on stands etc) that if I depress the brake pedal, I should see the pistons move? If this is the case, would that tell me if i have a seized piston? Or is the piston likely to pop out of the caliper altogether?

thanks
 

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Remove the pads and put in some spacers the thickness of the backing plates and see if the pistons move. The other issue with these brakes is that as soon as rust appears the pad never really gets enough use unless you are doing a lot of hard stops so the rust doesn't clear and being harder than the disk it wears the pad and the problem gets worse. I try to do some long hard stops every week or so just to keep the rears on shape and keep the rust away. 9-5's and 9-3ss use a much better setup at the rear.
 
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