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Registered
2003 Subaru outback sedan 4 cylinder legacy
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4 Posts
Discussion Starter · #1 ·
Hi y'all.

I'm driving a bit of a rust bucket, but am trying to fix her up. Did the rear brakes over the winter and it went smoothly, and now am doing the fronts.

I was surprised when I encountered the dual cylinders, but I kinda knew how to deal with them I thought.

Anyways, on to the interesting bit. The bleeder screw is open and the seals around the pistons won't properly retract, so they'll rub on the brake pads at the moment. The pistons will retract as far as I would want, but it's just the seals. Anyone have a good technique for getting the rubber bits back where they belong?
 

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2006 WX8, 59E
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1,184 Posts
So the piston boots are not folding the way they're supposed to. I would suggest rebuilding the calipers, especially if they're original to the car. It wouldn't take much more time than fiddling with the boots.
 

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2012 STI, 2007 Impreza RS
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261 Posts
If the piston boots are not retracting with the pistons, I'd guess some brake fluid got past the piston seal and is in the piston protector boots. This would cause the rubber boots to not retract properly.
 

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2009 3.0R Outback
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739 Posts
Sometimes you just need to take a pick tool and pull the boot away from the piston to release any trapped air. Don't use a pick with a super sharp tip and be careful not to pierce the boot.
 

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337 Posts
Okay so it's unlikely multiple things are true at the same time. Either
A) the piston did not go flat and the boots are still seated
Or
B) the boots have pulled out of the groove and you were able to squish them flat and wedge them on
Or
C) the piston will not go flat and the boots are dislodged.

Either way you are going to need to attempt to press the pistons back in or you are going to have uneven wear on the pads and ruin the boots.

Step 2 is going to be watch a rebuild video and preform the steps. It's actually really easy although intimidating the first time. The hits cost about 8-12 bucks per side. You follow the video instructions, pop the pistons out, I had to do some very light sanding on the edge of the caliper rim to remove a rust ring which was preventing me from seating the piston. With the caliper off the car and disassembled and bleed screw out the pistons should drop right in and slide back and forth smoothly although slowly do to the tight fit. If the pistons move freely follow the directions and put the caliper piston and boots back together.

After typing all.of the did you use a brake piston compression tool when you did the brake job or a c clamp? Also if you used a c clamp did you use and old brake pad to ensure that both pistons went back evenly?

Good luck

Sent from my SM-G965U using Tapatalk
 

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Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,905 Posts
The boots on the outside are for debris. The seal INSIDE the caliper is the fluid seal and it also pulls the piston back in when the pressure is released.

As @Plastixx posted, you can use a tiny screwdriver or a pick and pull the seal away from the piston head to release the trapped air and it will retract.
 

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2003 Subaru outback sedan 4 cylinder legacy
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4 Posts
Discussion Starter · #8 ·
Thank you everyone for telling me to do a piston rebuild! It turns out there was some fluid between the boot and the cylinder, but a rebuild got it able to be reassembled on the car.

My mistake was not using the old brake pad when compressing the wheel cylinders initially. I got one of them pushed out too far and that caused the problem I believe.

As far as how rusty the cylinders were, there was no internal rust so I think it's usable in the future. Currently focused on passing inspection in August then I'll hopefully be able to better justify real maintenance.
 
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