Changing rear brake pads on a 2003 Blazer LS 4WD with 4 wheel disc's 2 door with 105k. I bought Adv Auto Parts Wearever Gold ceramic pads p.n. GNAD 729 $38.99.
Came with all new SS brake hardware. Everything fit great and the pads are nice and thick.....slotted and chamfered. The 'thick' Pad part is the problem. I have used a six inch C clamp and one of the old pads and compressed the caliper piston/single on the rear/ into the caliper. I used the trick of loosening the bleeder valve to allow the piston to retract into the caliper without forcing the old brake fluid back into the lines and causing problems. This worked to a degree: the fluid dripped out of the bleeder valve and the piston retracted but not all the way. The caliper won't fit over the two new pads. I have tried compressing the cal. piston three times now and it will not go all the way in. I have the bleeder screw almost all the way out and the piston won't compress any further. What could be keeping it from compressing all the way in?
Any suggestions on how to get the piston compressed all the way in?

 

Please give me your ideas. I now have both rear wheels off and am ready to tackle the second rear brake. I passed the time by rotating my 'new' tires front to rear. These stock size Hancook's have really worn well. It is hard to tell which tire came off the front vs the rear. IOW no rounding of the front tires shoulders. I have checked the U Tube for ideas and one from Eric the car guy is before you replace a caliper because you think it is locked up as in frozen is to pinch the brake hose with a needle nose Vice Grip with fuel hose on the jaws to protect the hose. Then you remove the bleeder screw to clean the center hole. If the B. screw is blocked, it will appear the caliper has seized. A cursory look at the passenger side pads shows they are not worn much at all. Maybe the driver's side wore out those pads because the caliper had seized? I am speculating now!

 

Caliper pistons are stuck from corrosion. Replace the calipers. It's common.

 

You might try taking the bleeder screws all the way out. Even unscrewed a bit I would think you should have gotten more brake fluid than just some dripping.

Of course you will have to bleed the brakes if you do this.

Have you compared the pad thickness to the specs for other new pads? Perhaps the pads are too thick, were manufactured incorrectly, or mislabeled.

 

I think the pad thickness are correct. I double checked the part no. when I picked them up at Adv Auto. I am afraid the caliper is seized, but don't understand why it compressed with the C -clamp half way before it stopped. My next step is to remove the bleeder screw and clean the hole with a pick. If you pinch the brake hose with Vice Grips there will be no air introduced into the system.
Captain Hook always said to automatically replace the calipers when you replace the pads. Now I know why. I thought he was over reacting.
Tomorrow I will remove the other rear caliper and report on the condition of those pads.

 

It is because as the pad wears, the part of the piston bore where piston is most compressed has been exposed the longest to the fluid (moisture in fluid) and is most corroded. Also, as you compress the piston the seals scrape off junk and it gets trapped underneath. Just replace them and make sure you keep the master cylinder reservoir full of fluid while doing so.

Used to be caliper bores were steel. These are aluminum and thus corrode and pit more easily.

 

Les, you are right! As Captain Hook said: the caliper is aluminum, the piston is steel, and the brake fluid is hydroscopic. Results is corrosion between the piston and cal. bores.
I was hoping to put new pads in and be back on the road. I am dreading the replacing of a caliper because I have never done it on a Blazer and don't know about the complex parking brake mechanism lurking in the center dome of the rotor. I have had bad experiences with rear GM drum brake adjustment. The instructions say: just spin the rotor and tighten the E brake adjustment 'star wheel' until the shoe just starts touching the brake. That is easy to say and hard to do. One of the problems is the wheel doesn't spin freely due to the rear differential.
I will still take a look at the opposite side pad wear and also clean the bleeder screw opening and see if the piston will retract/ compress as it should. If the opposite side pads are not severely worn, it will be an additional indication that the driver's side cal. is, in fact, seized. Back soon with a follow up report.

 

Just back from a look at the opposite side caliper /passenger side/ and the pads were worn / little less than 1/4 inch/but not to the extent the driver's side pads were. New problem: on this passenger side, the upper cal. pin or slider bolt was stuck! The lower pin was as it should be. Once you removed the 12 mm bolt , the cal. pin was spinning freely and came out easily. On the upper cal. slider, it took over 45 min.s to get it to move with a 17 mm wrench on it. I had a long breaker bar to just get it to 'break loose'. So with WD-40 and a 17 mm , I am working it and turning it , but it is a long way from releasing and coming out! If I get the pin out, does that mean I can re-use that Caliper or does it mean I need a second caliper? How do I clean the bore of the old cal. ? Also, what is the best caliper to buy? Where is the best store to purchase it?

 

I have found my needle nose Vice Grips and a section of fuel line to create a pinch pliers that will not damage the brake hose per Eric the car guy on You Tube. So now the next step is to go back to the driver's side rear brake and remove the bleeder screw completely as Christine suggested. That allows me to clean the internal passage in the bleeder screw. Then I will try---again--- to compress the brake cal. piston. If it doesn't compress enough, I will be forced to pick up either one or two calipers. Anyone had good luck with a certain brand? See my questions above in post no. 8. TIAFYR, Jim

 

Recently I've been overhauling my brake calipers (front & rear). In my ride, the rear calipers are aluminum casts with Carlson pistons #7825. The pistons are made of synthetic material.
I've disassembled everything. After all I could say:
- the most common problem I had were brake caliper guide pins that stuck for real good. Guide pin boots seemed to be OK, despite that I had to spend lots of time & WD-40 to get them out. The guides & guide boots can be bought separately as kit
- I took the piston out. Air compressor is a handy tool, but bear in mind to cover the caliper with a rag or something. You don't want the brake fluid stains all over
- I did not notice any significant wear of a piston socket into the caliper cast. Just replaced the sealing & boot, put a film layer of special non-metal grease on a cylinder and put it back. It went all the way down till hit the dead end of. The seal and boot are sold as another repair set.

Later on I've bleed the line and everything is perfect. So I am curious of how would that wear look like in a case of steel piston & aluminum caliper. I'd be grateful for posting a photo.

@Jim
Don't be afraid, the brake caliper is not related to a parking brake mechanism. The parking mechanism is set under the rotor, the caliper on top of it. You may unscrew the caliper bracket with no doubts. Just make sure You detach the brake fluid hose (the liquid will drip out very slowly so set a jar or something underneath) - don't let the caliper dangle on brake hose. After all remember to top up the master brake fluid tank (with a new liquid, don't use that, what drips off meanwhile) and bleed the calipers.

As for the stuck caliper replacing - once I've taken mines out, surprisingly I found their surface in a good condition. I've just cleaned & greased the sliding part. I made sure they can glide in till the end of a socket. Check out Yours, it might not be necessarily to replace them.

Oh, and one more, friendly advice. Always start with the bleeder screws. Be gently while using a force. If they get damaged while releasing You may skip all the overhauling procedure and head on to the store to get a new one caliper.
Cheers, Mike