Can't compress rear brake piston

[wdrlaw]

So, started what I expected would be a two-hour job replacing front and rear pads on my 2009 GT. Left front, fine. Left rear, fine--including using "the tool" to compress the piston. Right rear, uh, something ain't right. The tool engages the piston and turns it, but the piston will not compress back into the caliper. Have I broken something? Is there an alternate approach? This is not my first rodeo with Ford rear brakes, but it's the only time I have turned the piston and it won't go back into the caliper. Thanks to the forum in advance for your help.

Oh. Right front, fine.

 

[saleen836]

Have you removed the cap from the brake fluid reservoir?

If not you are probably trying to force the piston back against pressure

 

[wdrlaw]

Have you removed the cap from the brake fluid reservoir?

If not you are probably trying to force the piston back against pressure

Yes. Had forgotten about that during the "left rear" task but remembered for the problem corner.

 

[Juice]

Did you turn it enough? I seem to recall, sometimes it took quite a bit of turning before the piston actually started to go back in.
It can be a PITA to do rears for sure. And both sides turn to the right IIRC. You do have to also apply pressure, not just turn the piston.
Thats all I got.

 

[Laga]

Open the bleeder screw.

 

[wdrlaw]

Open the bleeder screw.

Of course!

 

[JEWC_Motorsports]

Are you using an actual ford tool or just the pos block that you can turn?
The pic is of the proper tool.

 

[MasterofDisaster]

When I did this job a couple years ago, the left rear caliper was so bad I had to put a cheater bar on the caliper tool. Once I did that I was able to turn the piston back into the caliper.
Not sure why it was bad. I bleed the brakes once a year, and the fluid looked good.

 

[wdrlaw]

Are you using an actual ford tool or just the pos block that you can turn?
The pic is of the proper tool.

View attachment 82019

That's the tool. It will turn (to a point) but it would not compress even with the cap off of the MC reservoir. So:
1. Opened bleeder screw (genius tip, BTW). No joy.
2. Removed e-brake cable. No joy.
3. Bolted caliper and bracket to wheel without rotor, to get more cleavage. No joy.
4. Removed brake line. Lots of fluid, but no joy.
5. Removed caliper entirely, put it in a vise, and turned the tool. Easy peasy!

Thanks for all the suggestions. I don't know why it was so stubborn.

 

[redfirepearlgt]

I had this problem on my 99 F150 on the passenger side front. Turned out to be the rubber brake line between the caliper and steel line. The same happened on my fathers 2011 on drivers side and was the rubber line on that side.

What happens is the inner lining will collapse and create a check valve effect. Pressure from the pedal will overcome the restriction however when the brake relieves after releasing the pedal the pressure is not enough to overcome the restriction and it acts like a check valve. Even compressing with a c-clamp or the tool shown above will not overcome it. If anything damage can be done to the caliper trying to force it open...learned that the hard way months after the fix and had to replace the caliper also.

The hose will look fine when examined. The outer lining shows no signs of the inner lining/wall collapse. It can also happen where the line is clamped to the frame.

As mentioned above the best bet if you experience this is to disconnect the caliper from the brake line and see if the caliper then presses in with little effort.

The guy helping my dad do his did not believe me when I told him this. After he had dad buy a new caliper and it still did the same thing he then replaced the line and the problem was resolved.

Craziest thing I ever saw.

 

[wdrlaw]

I had this problem on my 99 F150 on the passenger side front. Turned out to be the rubber brake line between the caliper and steel line. The same happened on my fathers 2011 on drivers side and was the rubber line on that side.

Nice catch/tip. I don't have any rubber brake lines, so.... I went through the entire list before I got the piston to retract.

 

[redfirepearlgt]

Maybe you just needed to eat some more Wheaties?

 

[tomzstang]

No rubber brake lines? There should be one for the rear where the brake line travels from the body to the axle, but since you already successfully did one side, this wouldn't be the cause anyway. I have found some of these are very stubborn, especially once the pads have worn really low. The last case I had, the prior owner had installed both inner pads on one side and outer's on the other. The one side wore out very fast and I had a very hard time getting the piston to retract. Seems to me the piston can come out past the e-brake screw and if you don't hit the right location when turning it back, it can jam up.

 

[wdrlaw]

No rubber brake lines? There should be one for the rear where the brake line travels from the body to the axle, but since you already successfully did one side, this wouldn't be the cause anyway. I have found some of these are very stubborn, especially once the pads have worn really low. The last case I had, the prior owner had installed both inner pads on one side and outer's on the other. The one side wore out very fast and I had a very hard time getting the piston to retract. Seems to me the piston can come out past the e-brake screw and if you don't hit the right location when turning it back, it can jam up.

Replaced the OEM lines with Steeda S/S braid.