Brakes - Piston Dust Seal

Danbear09

Member
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Mazda 6
My question is: what keeps all the brake fluid in the system from leaking out if you disconnect the brake line? Either you've gotta crimp the line or plug the end with something, right?

I'm trying to repair a damaged piston dust seal that I discovered when replacing the pads and rotors on my 2014 Grand Touring AWD CX-5. I've read through an older how-to that was excellently written...it also seems to jive with other internet resources I've read:

https://www.mazdas247.com/forum/sho...o-Replace-Front-Caliper-Dust-and-Piston-Seals

I'm also referencing my FSM, but it's really not terribly useful for a first-timer to this job. My understanding is that you basically remove the caliper from the vehicle and use compressed air to force the piston out (gently as possible), inspect for pitting, corrosion, etc, and reinstall/lube the new seal. I am also intending to change/bleed the brake fluid in the system after performing the repair (Only one piston seal needs replacing).

Since I'm only changing the dust seal, is it possible to remove & replace while the piston is still on the caliper (leaving the fluid seal in place)? I'm thinking that getting the new seal on would be much tougher to do leaving the caliper connected. But to remove the caliper you gotta disconnect the brake line, and no video or how-to that I've read yet addresses what to do with the line that leaks fluid once you disconnect it...that's how I get to my original question. Any advice or pointers would be appreciated.
 
My question is: what keeps all the brake fluid in the system from leaking out if you disconnect the brake line? Either you've gotta crimp the line or plug the end with something, right?

I'm trying to repair a damaged piston dust seal that I discovered when replacing the pads and rotors on my 2014 Grand Touring AWD CX-5. I've read through an older how-to that was excellently written...it also seems to jive with other internet resources I've read:

https://www.mazdas247.com/forum/sho...o-Replace-Front-Caliper-Dust-and-Piston-Seals

I'm also referencing my FSM, but it's really not terribly useful for a first-timer to this job. My understanding is that you basically remove the caliper from the vehicle and use compressed air to force the piston out (gently as possible), inspect for pitting, corrosion, etc, and reinstall/lube the new seal. I am also intending to change/bleed the brake fluid in the system after performing the repair (Only one piston seal needs replacing).

Since I'm only changing the dust seal, is it possible to remove & replace while the piston is still on the caliper (leaving the fluid seal in place)? I'm thinking that getting the new seal on would be much tougher to do leaving the caliper connected. But to remove the caliper you gotta disconnect the brake line, and no video or how-to that I've read yet addresses what to do with the line that leaks fluid once you disconnect it...that's how I get to my original question. Any advice or pointers would be appreciated.

It'll be a slow drip unless you take the master cylinder cap off, then it'll leak out rather slowly. Either way you should do a bleed after you disconnect components like that.
 
Ok thanks. Oughtta be straightforward then, even if it takes me a while to replace the dust seal. I'll hook everything up afterwards and do a bleed in the order of RR, LR, RF, LF and be good to go.

Appreciate the help! I'll report back if I learn anything else.
 
Definitely appreciate the advice! It gave me the confidence to tackle the job. Took me a while to get the time, but I just finished the job. I left the Master Cylinder capped liked you suggested. I only lost about a thimblefull of fluid while I replaced the Piston dust seal. I did stuff a shop towel through the banjo bolt fitting just to help soak up the fluid (and maybe slow it down a bit). It was super simple. I bled the brakes afterward (which I needed to do anyway since the fluid was looking a little dirty) and all was fine.

Btw, the Motive Brake Bleeder is amazing.
 
Just in case anyone's curious, I bought the "0118 Black Label GM/Late Mustang 3-Tab Power Bleeder Kit" off of Amazon. The 3-tab design fit the 2014 CX-5 Master cylinder, and came with a couple of rubber gaskets of different thicknesses. Using the thicker gasket gave me a good seal to use the Motive Bleeder.
 
Congrats on the repair. It can be a little nerve racking opening up the brake system - so good job on getting it bled correctly following your repair.
Tip for next time: Before you begin your work push the brake pedal down and hold it there with a piece of wood wedged against the bottom cushion of the car seat. This pushes the master cylinder piston past the reservoir outlet - no brake fluid will drain from the reservoir.
Want to be super safe (and this applies to manual brake bleeding with an assistant pushing the brake pedal)?: Put a piece of wood or something about 1-2" thick between the brake pedal and firewall to limit travel. This way you won't damage the master cylinder piston by pressing it too far into an area of the cylinder that might damage the seal.
Don't forget you can always open the bleeder and use a c-clamp to compress the caliper if needed to get it off the rotor.
 
My question is: what keeps all the brake fluid in the system from leaking out if you disconnect the brake line? Either you've gotta crimp the line or plug the end with something, right?

I'm trying to repair a damaged piston dust seal that I discovered when replacing the pads and rotors on my 2014 Grand Touring AWD CX-5.
I guess my question is: how is possible the piston dust seal got damaged on a 2014 CX-5 GT AWD?

The front caliper piston and rear cylinder dust seals are still fine on my 1998 Honda CR-V with 185K miles. I was wondering if you can replace only the dust seal without removing the piston from caliper?
 
I damaged it myself when I was changing the brake pads - I wasn't as careful as I should have been when I was returning the rear piston to the retracted position. The tear in the seal was really really small, but I knew it would just fester into a bigger problem over time.

There may be a way to keep the caliper on the car for this job, but I didn't want to try that. I appreciated the working room I had when I was finagling the new seal into position. It also gave me a good chance to clean the caliper when I had the whole thing off.
IMO, it would take longer to figure out how to do the job without removing the caliper than it would to just do it.
 
I damaged it myself when I was changing the brake pads - I wasn't as careful as I should have been when I was returning the rear piston to the retracted position. The tear in the seal was really really small, but I knew it would just fester into a bigger problem over time.

There may be a way to keep the caliper on the car for this job, but I didn't want to try that. I appreciated the working room I had when I was finagling the new seal into position. It also gave me a good chance to clean the caliper when I had the whole thing off.
IMO, it would take longer to figure out how to do the job without removing the caliper than it would to just do it.
Thanks for explanation.
 
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