rmoss25

I am not able to compress the front brake calliper pistons on a 2021 GMC Sierra. I was able to compress the 2 pistons facing the towards the outside of the tire and one of the pistons facing the inside of the truck but one of them wouldn't move even when I tried compressing it with a C - Clamp. I let the truck sit overnight and when I tried compressing them I was able to compress all 4 by hand. I opened the truck door and I heard the system come on and I am now no longer able to compress them again. The truck is in brake service mode as well. I pumped the brakes a couple of time and the pistons moved out and they are slowly leaking brake fluid. The issue is happening on both sides, so passenger and rivers side front callipers. Is there a trick to compressing these pistons that I am missing?