I am pretty new to working on cars, and i thought i would do my own brakes this time. I had to replace the piston dust seal and now i can't press in the new one. Any suggestions on how to do this? Thanks.
If it's the same part I am thinking of, here is how I have done it in the past.
Before you put the new one on, there might be some dirt and rust build up on the edge of the caliper. Scrape/clean that off with the side edge of a flat tip screwdriver. Use a little brake fluid on the outer edge of the new dust seal to lube a little. Don't use any kind of grease. It's good work habits to only use brake fluid when working on or near brakes. You will have to find some sort of piece of pipe, big socket or something that fits the outside edge of that seal. So you can tap it in.
Is it just the dust seal or piston seal also? Is it pressing into the calliper or fighting to get it over the piston? If your fighting to get it over the piston, just install on the dust seal without the piston in place. Then use an air gun to blow air in the brakeline hole and push the piston up to it. The boot will kind of ballon out and over the piston. After that just use a C-clamp to push the piston the rest of the way in. Also use lots of brake fluid for lube!
it's just the dust seal on the outside. It will not press in without the other side popping back out. I'm using sil-gylde to lube the dust boot. The screwdriver idea sounds like a good one.
You have to remove the piston as a rule, and if you do that, you need to replace the seal as well. There is a special rubber lube for piston seals, it should come with the rebuild kit.