Caliper pistons install

[smalltown]

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.

 

[SARG]

Yup
Your second thought would have been my first. Over the years I've learned there are certain things to avoid and the better way to go .... such as using complete strut assemblies.... caliper assemblies and another .... I never work on exhaust systems anymore.

 

[Fishn1]

If I remember correctly, some of the Fords would actually screw in the caliper, a tool just for that purpose is made. Are there notches on top of piston?

 

[johnyg]

cut your losses and go with the re-man. if you do get it together would you feel comfortable with it??? like c/v boots....a r/m axle is cheaper than the kits and solvent you need to fix it. its a different world.

 

[smalltown]

Fishin1 no notches just a round edge.

 

[Milton Shaw]

You install the dust seal in the grove and then use an air blow gun to gently stretch the boot over the piston as you push it in. This is how they have to be done on the single piston and it has been over 20 years since I have done them on a dual piston but as I remember it works the same way. I went to buying reman's and quite rebuilding my own about 20 years ago. Still have all the drivers that were needed for the GM metal ring seals.

 

[brownbagg]

you rebuilt, why? they are so cheap just to replace

 

[robalmal]

You install the dust seal in the grove and then use an air blow gun to gently stretch the boot over the piston as you push it in. This is how they have to be done on the single piston and it has been over 20 years since I have done them on a dual piston but as I remember it works the same way. I went to buying reman's and quite rebuilding my own about 20 years ago. Still have all the drivers that were needed for the GM metal ring seals.

Thats how I used to do them too. Haven't had to rebuild one for years, but I do know it is a skill. Like lots of the automotive trade, some jobs get easier with experience. I am sure there are utubes of how to do it.

 

[Seagoon]

you rebuilt, why? they are so cheap just to replace

Too lazy to read ALL of the first post?

 

[isb cornbinder]

At this point your choice is limited to buying reman or my choice, new. Your description of what you have done so far guarantees a lack of understanding the job and guarantees brake failure. There are liabilities that go with brake work. If the brakes fail and someone is killed or injured and your insurance provider can blame you for improper work, your liability insurance will disappear and you lose the farm, so to speak.

 

[LS6 Tommy]

You install the dust seal in the grove and then use an air blow gun to gently stretch the boot over the piston as you push it in. This is how they have to be done on the single piston and it has been over 20 years since I have done them on a dual piston but as I remember it works the same way. I went to buying reman's and quite rebuilding my own about 20 years ago. Still have all the drivers that were needed for the GM metal ring seals.

Thats how I used to do them too. Haven't had to rebuild one for years, but I do know it is a skill. Like lots of the automotive trade, some jobs get easier with experience. I am sure there are utubes of how to do it.

My old method too. I think it's admirable that you wanted to try a rebuild, but as others have said, my new method is to get rebuilts...

Tommy

 

[MagKarl]

Good for you for trying. You did and learned something. That's how you learn to fix stuff, you don't learn how to fix anything by replacing it.

 

[MikeF2316]

I don't know about those, but on the calipers I work on, the seals do not have a square cross section, there's an "up" and a "down". The side further in the bore has more rubber, so the hole for the piston is smaller.

 

[sberry]

When I started out all that stuff was expensive and all of it was rebuilt. Must have been in 80 or so, a wheel cyl for a Ford PU was over 30$, now they can be had for 11 in some places. I fixed one a while back, it was leaking and pulled it apart on the truck, honed it a few seconds, wiped it out and put the old seals right back in. Poured some fluid in it, never did empty the master.

 

[6768rogues]

You tried it and failed. You learned something. Buy rebuilts and get it over with.

 

[sberry]

I will agree that it is worth a try and certainly helps with understanding how they work to some extent. It also can help confidence with crisis repairs. As I mentioned I did one the other day, it saved a lot of work and money, didn't need to wait on a part on an old crate, didn't need to buy one and it worked as good as a new one would have.
But as a matter of general practice remans or new is the way to fly. Parts are so much, there is no skimping, there is often damage one can never really fix anyway.

 

[smalltown]

Just wanted to update, and close this post. Hopefully it will be useful to somebody in the future.

I searched, and read as much as I could about others trying to reinstall caliper pistons, and assembly fluid. I also tried in vain to get Centric the maker of the seals, and pistons to respond to my question about Centric assembly fluid.
Buried in their products listing I found the fluid.

As far as I can tell the fluid will not interfere with the brake fluid. The label states it can be used on all types of rubber seals, and caliper pistons.

I found the fluid on Amazon. The fluid didn't seem dramatically more slippery than brake fluid.

Surprisingly the pistons slid in much easier. I could "seat" the piston and feel the seal, and when I let of pressure the piston would slide back away from the seal. I was able to get the piston in with just a little help from a "C" clamp, and an old brake pad to center the pressure. Once the piston started I was able to press it in by hand. I've operated the pistons with compressed air, and everything is looking good. I am able to push the piston back in by hand using only moderate hand pressure.

I've reassembled the last front caliper, and one rear. Tomorrow I'll bolt them in place.

Things are looking up or should I say in !

 

[TJ041]

I rebuild my calipers as well, because Rockauto sells rebuild kits for just a couple dollars (ACDELCO 18H21{#18031495}Professional $4.16)(my application)
After Cleaning everything, I stick the piston in the freezer for a few hours/overnight and the caliper itself in the oven at 100 degrees. Pull it all out and, slap on the o-rings, dust cover, some assembly lube and it all slides together relatively easily.