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97 OBW/05 9-2x/08 2.5i
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Discussion Starter #1
97 OBW with about 176K. I'm putting the car up for sale shortly (I hoped this weekend), so I replaced the front rotors only as they were warped. I actually had a set of pads to put on as well, but they were just slightly too big and would not slide into the caliper (the little tabs were too big, perhaps a little Dremeling would fix that).

I used the old pads that were on there, they still had lots of life and visually looked to be fine. Since putting on the rotors (Wearever was the brand, from Advance Auto), I get a slight drag/squeal noise when the brakes are not being used. This noise was not there before. Once I get up to about 10MPH the noise begins and gets louder as you accelerate. As soon as I hit the pedal, the noise disappears and the brakes work fine. Also, I cannot tell if its from the driver or passenger side, or both. I did see a couple slight lines on the drivers outside rotor and the passenger inside rotor

I have taken the front brakes apart twice now, to thoroughly clean the clips and sliding pins and then relube them with grease. I have done basic brake jobs before with no issue, but this slight grind/squeal noise is quite frustrating.

The rotors fit on just fine, but they seem slightly less snug than the old rotors (which are long gone at this point). I almost wonder if they the looser fit allows them to become just slightly offset and drag against the pad.

The plan is to sell it ASAP, but I want the brakes to be right for the next owner and I want the cost to be at a minimum to me. My new Saab 9-2x is just waiting in the driveway to be driven, I have to fix and sell this first though!
 

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2011 SSM Outback 2.5i Premium
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Did you compress the piston back into the caliper? The new rotor is likely thicker than the old one, needing more clearance.
 

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97 OBW/05 9-2x/08 2.5i
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Discussion Starter #3
Yes, I did compress the pistons back in.

One thing I have not done, but I will after work today, is the proper bed-in procedure for the brakes. Such as this method, here.
 

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2005 LL Bean
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Did you clean and lube the slide pins? Did you clean the caliper at all? (where the pad backing plates ride)
 

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97 OBW/05 9-2x/08 2.5i
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Discussion Starter #5
I cleaned and lubed the slide pins, yes. They were not bad to begin with, but I did clean them again in hopes that was the issue. The rubber boots are in okay condition, not torn or cracked, but I imagine next brake job will require replacement.

I also cleaned the metal clips where the pads slide into. Of course, I regreased them (both the pins and metal clips). However, I did not clean/lube the back sides of the pads or caliper bracket. I saw no real reason to (I.E., rust or built up crud). However, the original pads had no shims on the backside of them. I do not have another set of shims to put on the car either.
 

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97 OBW/05 9-2x/08 2.5i
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Discussion Starter #6
Alright, I took a long lunch and tried out the brake bedding procedure. I only got about 8 stops from 55-60MPH, but it seemed to help initially. After the 8 or so brakes from 60MPH, I drove at highway speeds immediately after for 8-10 minutes without applying the brakes at all. I parked the car for a quick lunch stop and the noise came right back. When I parked the car, I coasted to a stop and left it in neutral while I chocked the back wheel, hoping to avoid any hot spots. The noise seems less noticeable now, but still there. I'm going to repeat the brake bedding procedure after work, hopefully traffic will be light enough for this. Fingers crossed!
 

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2017 OutBack Premier, 2019 Forester Ltd, 2016 370z Rdstr
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I live in the land of salt on the roads and high humidity at times of the year. It often takes its toll on brake systems if they're not serviced regularly. From what you are describing, it sounds to me like your caliper pistons are seizing up slightly.

Water gets into the brake fluid (particularly if it isn't flushed out every 4 years or so) and causes rust inside the calipers, and then causing the pistons to stick.

Remove the pads from one side, unbolt the top caliper bolt and swing the caliper up. Slowly pump the brakes until the piston pops out. Clean it with 0000 steel wool and brake fluid to remove any rust rings. Hopefully it won't be deeply pitted. If it is, replace it.

Then clean the caliper bore using the same method. Once clean, lube both with fresh brake fluid and reinsert the piston back into the caliper. Its tricky get stretch the rubber dust cover back over the piston, but with patience its done easily enough. (You might just remove the caliper from the car altogether and find the job easier to do). Clean everything with brake cleaner and reinstall the pads and all. Bleed that side back to normal, and then do the same on the other side of the car.

Hopefully your sticking piston/noise problem should be corrected. I've done this job on several different cars and it has worked every time. Good Luck!
 

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97 OBW/05 9-2x/08 2.5i
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Discussion Starter #8
Thanks for that detailed reply. Will I need to disconnect the brake line to clean the pistons and piston bore?

I will have to try that this weekend. I hope to have my other car on the road before I take apart this one, so it may wait until the following weekend. Having 2 broken Subarus is getting a bit frustrating :)
 

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.....
Water gets into the brake fluid (particularly if it isn't flushed out every 4 years or so) and causes rust inside the calipers, and then causing the pistons to stick......QUOTE]


Although I don't work on cars everyday, I have seen a lot of calipers in my day.
I have never seen rust on the inside of a working caliper.
Although the fluid is hygroscopic, it acts to lower the boiling point and therefore reduces efficiency. T'is why fluid specs give a dry and wet boiling point.
Your cleaning method is sound, but most of the time the sticking comes from the rusted portion of the outside of the piston. For whatever reason this part (it only takes a fraction of a mm) gets back into the bore and offers too much resistance for normal operation.
I've seen and heard of more sticking calipers just after new pad replacement than otherwise.

O.
 

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On the other hand, I've been a backyard gear head for close to 45 years and I HAVE seen pitted caliper bores. The only way to deal with that is to buy rebuilt or new calipers. The problem is that the pitting is usually where the piston seals ride and will leak. The pistons are usually aluminum or phenolic and, rarely, pit.

If you "push" those pistons out using the brake, do it VERY carefully or you'll end up shooting those pistons out quickly with a real mess. And, you should have re-build kits on hand. It will take one kit per caliper, which consists of the piston seal(s) and the dust cover(s). And, have plenty of new brake fluid on hand; you'll need it. You also might get some brake assembly lube for getting those piston seals back into the caliper. Again, if there's any significant pitting, that you can feel with your fingernail, it's replacement time.

Good luck.
 
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