Im in the process of changing my brakes and rotors after completing the job almost fully I was trying to decompress the piston and it wont budge on one side any ideas of what I can do? I was using a big set of pliers any help would be appreciated.

 

take the lid off the brake fluid reservoir

 

Are you doing front or rear? If it's the front maby try grabbing the piston with some big chanell locks and twisting it a bit to free it up. If it's that stuck it probly should be rebuilt or replaced. If it's the rear they are ratcheting and you need to twist them in.

The reservoir is vented. The cap will have no effect on pressing in the caliper piston what so ever

 

Oh hell no...don't be doing that! You can f-up your caliper and cause damage to the piston.

Instead...use a C-clamp with one or two blocks of wood. You definitely need one block of wood over the piston and maybe a second on the back depending on how big your C-clamp is. This will apply even pressure to the piston, thus not causing any damage to the piston or the seal.

And even though your brake fluid reservior may be vented (which I doubt) loosen it anyhow, it will help.

This guide is for the front calipers. The rear you need to twist them in a clockwise motion to compress them. Make sure you line them up properly after doing this (reference the attached picture below).

 

if none ofthose work, you can try to open up the bleeder screw and try to compress the piston then bleed the brakes after.

 

like 00semax said, is it the fr or rear. front you can compress in with a brake piston tool that you can pick up at any auto store. the rears actually screw back in. not sure which way. also dont that the cap off unless you want brake fluid all over the place. the cover being on the resevoir has no pressure keeping the piston from going in. If nothing works what i do is take the old br pad ( if this is the front) and take a piece of wood and and hammer it once or twice to break the bond. Brakes go thru so much crap that they can get temporarily stuck. if the rear spray with wd40 and wait. becarefull of the rubber seal when screwing back in. you shouldnt have to undo the bleeder or cap or anything. worst case senario is a frozen caliper which will need to be taken apart and rebuilt. if thats the case i would do both sides.

 

Get a C-clamp like suggested above, works like a charm.

 

If you grab it at the end it's fine. I agree don't grab anywhere the piston touches the seal.

This was just one of the things I've had to deal with while trying to unstick frozen calipers. I've even had to pull a caliper off the car, stick it in a vise, remove the bleeder, use a air nossle where the bleeder goes with a 150psi of preasure and do what I said above to get them to move before.

I know this is extreme but I've had to deal with some messed up cars.

And yes, I do have all the correct tools for brakes but extreme times = extreme messures.

In reallity if there is any problem pushing it in it should be replaced or rebuilt

Also removeing the master cylinder cap wont change a thing, I mean nothing. The only reason you should remove the cap is so you can stick a rag on top to try and soak up any overflow spillage (that will happen with the cap on also) when you push the caliper pistons back in.

 

sounds like you might need a new caliper.

how many miles on your car?

 

You also need to put a lot of wd-40 or machine lubricating oil

 

Thats what you don't want to do.patrolium products make all the rubber seals and dust boots swell up. All you want to use is assembly fluid.

All though it would be fine if you are going to replace all that stuff.

 

I see a lot of ppl bashing on WD-40 on here lol. B Careful.

 

if it won't go in with channel locks it's seized and you need a new caliper so that you won't wear out your next pads prematurely, burn more gas than neccessary and also so that if you achieve higher temps due to dragging brakes and achieve fluid boiling point you will not experience hydraulic system failure and cause your pedal to sink in stop and go traffic or if you need a panic stop.
I may be on the excessive side but in theory it does and has happened.
SO get a reman caliper with the new set of pads.

 

Glad i read this, i ran into this problem tonite while changing my front brake pads, i noticed the pass front pads wore uneven but the piston went in without much effort. Then get to the driver side everything goes well until i could not get the piston to go back in. I believe it is stuck n probaly the cause of most of my issues ive been experiencing where the car is sluggish, then all of a sudden power comes out of nowhere.