Caliper rebuild question

[smalltownusa]

I rebuilt my 2005 Ford Explorer Sport Trac front passenger brake caliper, and although the new pistons installed hard they went in.

I moved on to the driver side removed the caliper cleaned it up, and painted it. Now I cannot get either piston to install (no paint in the piston bore nice and clean). I've got one piston half in using a block of wood, and a "C" clamp. It went in pretty hard. I had hoped that at some point it would start to push easily, but no. I lubed the inside square cut "O" ring, and the outer dust seal liberally with brake fluid. I rolled the new piston in brake fluid, but it will not go in. I have broken the new dust seal on the piston before it would insert. Now I have the other piston half installed so I am in no mans land. I cannot put air pressure to remove it since one piston is removed. It's not on the vehicle so it's not pressure from the vehicle and the bleeder screw and the brake line are disconnected and open. I did try to install without the dust seal, and the trouble is getting the piston to slide by the cut O ring.

When I started to reassemble I first installed the cut O ring then the dust seal, and the piston last. I was thinking maybe I should install the O ring then slide the dust seal half way on to the new piston, and then try to install the piston.

P.S. I compared the old O ring and piston, and they look the same.
The only thing I have not tried is to reinstall the old piston using the old O ring just to see what happens.

Any thoughts ?

Yes before anybody suggests: If I had to do it over I would buy replacement calipers and be done with it, but I wanted to try it at least once, and I've got all the parts and pieces.

 

[shucker1]

Where did the pistons come from?

That's the only major part that changed.

 

[smalltownusa]

shucker1 from Rock Auto.
I just finished double checking part numbers and they are correct.
Maybe I should be turning the piston while trying to push it down ?
It just doesn't want to go by that inner seal.

 

[shucker1]

IF and thats a big If you can get the pistons out you might be able to open the bores a little with a brake hone that attaches to a drill motor.

Bores may be egg shaped from time. That is why the new round pistons won't go in.

You would be surprised what a .001 clearance can do..

 

[smalltownusa]

Thanks shucker1. First chance I get I am going to try and insert the old inner seal, and the old piston.
The Wife's got family reunion tomorrow so there will be a little delay.

 

[shucker1]

Take care of that first.

Family is the biggest thing.

 

[smalltownusa]

This afternoon I tried again. Frustrating to say the least. With no seal in the bore the new or old piston just barely slides in.
Tried the old inner seal, and the old piston can't get that in so it's got to be me doing something wrong.
I've looked at as many you tube videos as I can stand. Some use a special grease that came with their rebuilding kits??? I'm using only brake fluid.

shucker1 I took a look at brake hones, but I think that would only open the bore. If I have a problem with the "metal" it would be the depth of the cut grove for the square cut seal. I've compared the old seals and pistons they seem the same to me.

I have not given up yet.

 

[Joe in NY]

Good luck! We tried doing this twice. Once on our 2007 Suburban, and then a few weeks ago on my Explorer. The pistons just wont go in!!!!

From now on, only reman calipers when one sticks. NAPA usually has the best reman parts from my experience.

If you defeat this that's awesome! If not, welcome to the club

 

[shucker1]

I've compared the old seals and pistons they seem the same to me.

How? Visual Inspection? That does not count...

Don't mean to be a buzz kill but unless you have precision measuring tools you can't be sure.

You say;

With no seal in the bore the new or old piston just barely slides in.
Tried the old inner seal, and the old piston can't get that in so it's got to be me doing something wrong.

You have got to be perfectly square with the bore to go in. It's not easy but you have to take your time putting it together.

Like I said;

If you can get the pistons out you might be able to open the bores a little with a brake hone that attaches to a drill motor.

Bores may be egg shaped from time. That is why the new round pistons won't go in.

You would be surprised what a .001 clearance can do..