Hey guys,
Ive suspected im having a braking issue with my fronts. My pads dont seem to be forced from the caliper pistons to the rotor......I pulled the pads and wanted to see if pressure would force the pistons out. The lower 2 pistons were forced out but the tops didnt move, is this normal? It was the same on both front calipers....Ive suspected a caliper issue ever since I had sent them to be resprayed by a shop. They didnt prep them and sprayed over everything, pistons, seals, openings....everything!
Thanks in advance....

 

What exactly do you mean by "wanted to see if pressure would force the pistons out" ?

Also, did you do the install yourself? Did you make sure to bleed BOTH sides of the caliper? I.e. the caliper has 2 bleeder screws, did you bleed them in succession and in the correct order?

 

Depressing the pedal with no pads in there is a great way to remove the pistons completely from the caliper, requiring rebuild kits if they exist or whole new calipers if they don't. This isn't a Honda and ****ing up isn't cheap, use your head.

Also of note, bleed the **** out of that system, and do all 4 corners in the correct order. If the tops aren't moving, there's definitely air in those calipers still.

Paint on the pistons and boots doesn't matter, it'll crack and flake when they actually move anyway, if it doesn't straight burn off.

 

I wanted to see if brake pressure was forcing the pistons onto what would be the pads(I removed them just to see if the pressure would force them out and placed a wooden block in place of them so they wouldnt come out fully). I have bled the system multiple times in the correct order, and all the nipples. I did the install myself, I understand how the system works, Im thrown off why the pressure isnt moving the top two pistons on the calipers. Like I said, Ive been suspicious on there operation for a while now, theres no grab up front braking and I dont think my rotors are being wore down what so ever

 

I had planks of wood in between where the pads would be, I wanted a full view from where the pistons exit the caliper. I understand this caliper isnt a honda caliper and Im not asking to be called an idiot, Ive replaced my clutch, turbo, ect...I understand how the braking system works and they require bleeding in a certain order which I followed. I was simply curious as to if all 4 pistons should be forcing their way out. Im think There is something blocking the internal passages, like a crap ton of clearcoat and paint

 

Stupid question here but when you pulled the pads out and put said wood block their place did you actually press the brake pedal??

In other words the pistons are not just going to move out by themselves with the pads out.

 

I'm curious why wouldn't the piston still be forced out without pads, the brake pedal applies the pressure to the caliper and inturn forces the pistons outward, right? I wouldn't imagine the pads have anything to do with brake pressure being applied

 

You don't have enough fluid displacement to push both banks of pistons completely out, that's not how its going to work, if you stopped the 1st piston in motion the 2nd piston would than start to come out. Path of least resistance is what will move first.


In order for the system to build 'pressure' it must have resistance. The only resistance you have on a open caliper is the friction from the piston seals. That is why when you have a pad/rotor resisting the pistons from popping out, the pressure will build inside the caliper providing force on all pistons.

Make sense?

So if you want to see the top pistons move, put a block of wood between the bottoms... than you can pop out your top pistons lol

 

Ok, this makes sense....the block of the wood I used was not thick enough and the first pistons the fluid pressure came across and popped the pistons....the fluid then looses it pressure from the passageway behind these pistons. I just disassembled the calipers, I think Ill just do full rebuild and clean them up.....easier to understand when taken apart.....thanks for the help guys

 

Yes of course they would still be pushed out, you missed what I was saying. What I meant was that you would actually have to press the brake pedal in for the pistons to move out.

Meaning I wasn't sure if you actually depressed the brake pedal or not once caliper was off

 

the pistons are different sizes so the bigger ones will move first

 

My bad, yes I was referring to applying the brakes to build the pressure....Hard to explain things sometimes over messages