Changed rear brakes on car today, this was a fleet vehicle.
Had an issue on both sides: the calipers would not retract enough to fit over the new pads. I am used to the caliper cylinder retracting to almost flush with its casing, the best I could get these was about 1/2 inch from flush.
The only way I could get the brakes back together was to grind the pad friction material (mask and all).
Not a fan of GMs cylinder end profile - real pita to turn the cylinder with a two pin wrench.
Before you ask, the cylinder was able to be turned when I stopped turning it as it made no difference, the cylinder was not retracting.

I know there were some brake cylinders which were under a recall but my vin did not return any outstanding active recalls. Mine are TRW units with the following markings stamped in various locations: 0901 117 4 D 7 1/5.

Can anyone shed any light on this situation? I believe the calipers cylinders should have retracted almost flush, not sure why they wouldn't.
Anyone else have any similar experience?

Yes, I've done a lot of brake jobs before. Never had such a time as I did on this car.

Those get turned in not compressed. May require a scan tool.
'Cylinder was able to be turned'
Do you mean the piston?

Yes, I tuned them in using a two pin wrench adapter. Yes, piston - not cylinder. Still think the turn ins are a pita.
Have no desire to remove a caliper and put it on the bench to see what I can do with it.
Piston turned hard, did get it in the cylinder some.
I suspect something is going I am not aware of!

You need a scan tool.

Those are hard to turn in but that'* how they work.

I haven't had luck with them with the little "socket" adapter thing. They go in pretty well with the more expensive screw type tool like the auto parts stores rent.

I've looked this up and viewed several videos on this design and usage on the Impala.

I haven't broken the hydraulic lines and don't need to ABS or otherwise bleed the brakes, I do have a scan tool that performs that function however.
What good would a scan tool do for me here? FWIW There are no codes set.

It is obvious to me that the calipers still have issues. I've changed the brakes on my DTS which have the same design; screw in pistons - they turned in with much less difficulty than these.
I expect I will be revisiting these within a year or two. It is possible that the flex lines to the calipers are also breaking down internally.

Hey, CathedralCub, What tool is it that the auto parts store rent out? I have two different styles both of which require a 3/8 drive wrench. The cube won't work at all here, the adjustable 2 pin works with difficulty.

I'll wait for the next rear brake issue then just replace the rear hoses and calipers. Just be done with it.

Use the scan tool which I think opens the dump valve so you can retract that piston with ease.

I doubt this is the case unless there is some major backstory that I'm not aware of.

It'* a kit that has a couple of c-clamp looking things and lots of interchangeable pieces to use based on vehicle.

I hadn't thought of this. Yes this will make it go more easily. I just twist on these really slowly instead.​​​​​​​

Thanks for the feedback to both of you.
I wasn't aware there may be a dump valve option with the scan tool.I've used the ABS bleed on my DTS, scan tool with this feature is new to me.
You can believe though that I will check this out on my scanner (D7)
I am not a professional mechanic, been working on cars for over 55 years - but that doesn't make me an in the know mechanic. I o miss the points and distributor though, and the access to various items in the engine well.

The flexible lines may or may not have issues. Had a flex line issue on my Ram diesel which ruined a caliper and front wheel bearing. Hoses are cheap compared to what that plugged line caused. Read an article on how these lines could fail on the Impala, as the one in the RAM did.
BTW the RAM is now someone else'* vehicle.

Something about the rear brakes didn't seem right to me when I was working on it. Can't point to anything specific but the corrosion, wear pattern on the pads and rotors, and general appearance made me think that the rear brakes had not been properly working for some time.
Worked the pistons slowly, had to as the tool kept slipping off the head of the piston. As I said, turned quite hard, I typically was able to get less than an eighth of a turn each time. When it appeared not to be retracting any further I stopped! Turning was more difficult at that time.

I am not happy with the work I did on this car (my wife'* car) but I believe the brakes are in no less of a safe working condition than before I started this work. Wife is not driving for a while, knee replacement, so I will be driving this car rather than the one I normally drive, and keep track of the rear rotor wear patterns, etc.

Sounds like you're heading in a good direction with this repair.