How to Replace Pistons and Seals in Echo TR Hydraulic Disc Brake Calipers

About This Tutorial

After dealing with leaking Echo TR disc brakes a couple years ago, I decided to rebuild my calipers by replacing the pistons, piston seals, and bore cap seal. I am totally not mechanically inclined, so it was a small win for me that I was able to do this project with much trouble. I figured I’m probably not alone, so I documented the process as I did it in order to create this video tutorial. It’s certainly not my best work, but hopefully it’s useful to anyone needing the fix their bike’s leaky hydraulic disc brakes.

In addition to the tutorial video, I’ve posted the transcript as well, below.

Video Tutorial Transcript

Good working brakes are critical for riding trials unless, of course, you ride brakeless. I don’t.
My Echo Mark V 24 inch trials bike came with Echo TR hydraulic disc brakes in the front and rim brakes in the rear. After suffering poor brake performance for a while, And replacing contaminated front disc brake pads a couple times, I finally realized that the contamination wasn’t due to anything I was doing to the brake rotor.

“I don’t have any front brakes. The, uh, Echo brakes that I have, the disc brakes, are leaking like a sieve.”

The mineral oil used as the brake’s hydraulic fluid was seeping out around the piston seals, and contaminating the brake pads. I guess I could’ve just removed the front wheel entirely, but that just isn’t very practical and makes the idea of gaps and drops somewhat terrifying.

The purpose of this tutorial is to show you how to rebuild your Echo TR hydraulic disc brake caliper with new pistons, piston seals, and a bore cap seal if your brakes are leaking like mine were. Now I am not at all mechanically inclined. If I can do this, anyone can do it.

Tools and Parts

You’ll need some basic tools to perform maintenance on your Echo TR disc brakes. To rebuild my caliper, I used a set of Allen keys, or hex wrenches, needle nose pliers, a hydraulic brake piston press such as the Park Tool PP1.2, an 8 millimeter box wrench, a metal bar to open the bore cover (I could not find an official bore cap tool from Echo), a plastic tray to catch the brake fluid, some clean rags or paper towels, a hydraulic brake bleed kit, fresh mineral oil brake fluid, cotton swabs, small wooden skewers or something similar, a small spray bottle, and plenty of isopropyl rubbing alcohol. A pair of vice grips could come in handy as well.

Before you start, you will also need 2 new Echo TR pistons and 2 new piston seals While the leak could be due to the seals, it is also possible that your pistons have some scoring on the sides which can also cause the mineral oil to leak out. Since you’re already opening up the bore cap, you should also have a new bore cap seal. And of course you’ll need new brake pads and possibly a new rotor.

Starting Assumptions

This video assumes you’ve already removed your brake assembly from the bike, and removed the brake pads from the caliper. Let’s get started.

Removing the First Piston

I’m gonna show you how to take the pistons and the seals out of a set of Echo TR calipers for disc brakes. We can see the pistons right in there and if you gently apply the brake pressure, it slowly starts to push the pistons out and what you want is you want the piston that’s the outboard one, not the one next to the bore cap. You wanna do the bore cap one last.

When the one closest to the bore cap starts to come out you can push that in and just keep pumping. You can try to get the piston out here Now my brakes have leaked quite a bit, so it’s hard having enough pressure to get these pistons to come out. I didn’t have enough mineral oil left in my brakes to actually push the pistons out so I attached a bleed syringe with some oil in it so now I’m just gonna gently push from the syringe to apply some pressure to push out the pistons here. And again, I want the outboard piston to come out first and then the inboard piston, I’ll take that out when I take out the bore cap and access it that way. Ok, so now I’ve worked the piston all the way out. Now I just need to to pop it through. Alright so there we go, there’s one.

Removing the Bore Cap

And now I’ll take the bore cap off to get the second one out. So, since I can’t seem to find a tool to open up the bore cap on my Echo TR disco brakes, I’ve decided to take this piece of metal bar here that fits in here and we’ll see if we can give this a go. I’ve got some locking pliers here to hold it steady. Unfortunately it’s kinda chewing up the bore cap.

Removing the Second Piston

And now that the bore cap’s off, we should be able to pop the other piston out fairly easily. So you do need to push the piston with a good bit of force but you don’t want to use a sharp tool because it will
score up your brakes and you really don’t wanna do that. That’s the second piston out. So you can see now the inside of the Echo TR brakes. The seals have to be replaced too so the next step is to get the seals out, put the new seals in.

Now that the pistons are out, I can take the brake hose off and then put this where it won’t leak out. Before putting in the new seals and pistons, you wanna do a nice job cleaning out the caliper. One thing that works well with that is isopropyl alcohol, rubbing alcohol and you can use a Q-Tip also to do some cleaning. You can also use a rag to reach down in and really get it all nice and clean.

Replacing the Piston Seals

To get out the seals, you need something sharp but preferably non-metallic. You don’t want to score the inside of your calipers but you have to pry out the seals so I’ve got these wooden skewers.

So before putting in the new seals, we’ll just do another real quick cleaning to really clean out around here the old seals were. Before putting the new seals in, it’s good to get them a little bit lubricated. Helps it go in a little bit easier, so I’m just gonna use a Q-Tip here and some mineral oil since these are mineral oil brakes.

And to put the seal in, you kind of fold it up and work it into the recessed location. Bit of a bear to get it in there. Just gotta work it gently, make sure it doesn’t have any kinks. That’s the first one in.

We’ll lube up the second one and do the same thing. Stick it in; you can kinda feel where the the recess is that the seal was supposed to go into. If you can get one end of it in, you can kinda work the rest of it down. Now just check with your finger, make sure that it’s in the right way and it’s not all twisted or your piston won’t go in if it’s sticking out and if it’s twisted it’s gonna leak. There we go, we’ve got both seals in.

Don’t know if you can see that in there. To put the pistons in, you also wanna lube these up a little bit too. You can use a Q-Tip and put a little bit of the mineral oil around the sides of the piston.

Reinstalling the Pistons

And what we’re gonna wanna do is for the first piston that we put in, wanna put in the one that’s farthest away from the bore hole. So you wanna work that in there. Wanna make sure that it goes in nice and straight and you don’t want it to bind. When I was pushing it in there, it kept wanting to pop back up again so I didn’t know if the seal was sliding down but now I think I got it.

So to get the first piston all the way in, you can use a brake tool like this one to gently push and make sure that the piston goes in level all the way through so it doesn’t bind up. You’re gonna need it all the way down so that the top piston on the bore hole side can fit in.

Now we’ll put the second one. We’ll lube up the sides with a little bit of mineral oil. Little bit of a challenge to get the second piston in. But here’s where if you have one of these brake tools, you can gently push and work the piston past the seals. When you first push it, it doesn’t want to go past the seals, it wants to hang up a little bit. You can see now I’ve got it partway in, not quite all the way, so I’ll keep working it with the piston tool here. Again, applying steady pressure all around so that it recesses nicely and evenly and doesn’t bind.

Alright, so there you go, now you can see that both pistons are all the way in. You can see with the second piston in looking through the bore hole you can see that the piston is past the seals. That’s the way that it should be.

Replacing the Bore Cap Seal and Bore Cap

While you’re rebuilding your Echo TR calipers, you may also want to replace the seal in your bore cap. Again, pry off the old o-ring and pop in a new one. Let me clean this off a little first using some rubbing alcohol. Get it all nice and clean around where the o-ring was to make sure it seals up nice and tight with the new one. Pop the new o-ring right on. And then before we put the bore cap on, like we did with the piston and the seals, we’ll just put a little bit of hydraulic oil around the o-ring here to help it go on without binding.

You can put the bore cap right back on. Just like I took off the bore cap with a metal bar, I’m gonna use the metal bar to put it back on also.

Final Steps

After rebuilding your caliper, you’ll need to do a few more things before your brakes are ready for use again. I’m not going to demonstrate them all here, but to summarize, you will need to reattach the brake hose to the caliper, fill and bleed the brake assembly, install new brake pads, clean or replace your existing rotor, and reattach the brake assembly to your bike. Before you install the new brake pads, make sure you wash the caliper with soap and water, rinse it well, and then spray and wipe with rubbing alcohol and a clean rag or paper towel. If you decide to keep your old brake rotor, make sure you clean it really well with soap and water and then spray and wipe with rubbing alcohol and a clean rag.

Thanks for Watching!

If you like this video, please give it a thumbs up. If this tutorial helped you rebuild your bike brakes or if you have any good tips that could help other riders with an Echo TR caliper rebuild, please leave a comment.

Thanks for watching, and happy riding!