I had a 89 Prelude. I use C-clamp to push the piston back. I tried the same
thing on my 93 Accord, it won't move at all, almost break the c-clamp. When
I read the service manual, I noticed it described to use a pair of need nose
pliers to twist the piston and turn, and it worked. Don't know about the
prelude. But are you following the service manual?

Paul