How badly did I mess this up?

[Dumbmonkey]

Hi y'all,
81 XS, mostly stock here...
I had an issue with my front brakes locking up on me last week, and after rebleeding all seemed ok except it felt like they were still dragging a little bit. I took the caliper off today and pulled the pads to check the piston for damage. All looked fine to me as far as I could tell. I used the brake lever to extend the piston a bit and applied some caliper grease around the exposed area as well as on the surfaces that the pads move against. I couldn't get the piston to push back into the caliper, so I released pressure by opening the bleed screw. I got it all back together and now I can't seem to build any pressure in the system to re bleed the thing. I can't seem to figure out the problem and I seem to be going through an awful lot of brake fluid with the mighty vac. Could I have pushed the piston back in too far? Any suggestions?
Arrrrrrrgh....

 

[torider]

Have it overhauled. Dirt, dust or even rust may be the reason for the lock up of the pistons.

 

[angus67]

overhaul the mc and caliper, and get a new brake line. the rebuild kits for the caliper from mikesxs are acceptable. I haven't rebuilt a mc, I baught a new one to avoid the hassle, so I couldn't tell you if mikes kits for mc's are worth it.
You didn't screw anything up, you just got some crud blocking return pot in the mc.

 

[Opus5150]

Check that you aren't rolling, (and tearing), the rubber gasket with the piston as you push it in. I rebuilt my 75 front caliper with the Mikes XS kit and its worked fine. Good luck!

 

[Dumbmonkey]

Hey everyone!
Thanks for all the responses and advice, I really appreciate it. My master cylinder and stainless brake lines are only a year old, so I'm assuming that they were ok. I disassembled the caliper today and cleaned it all out. There was some pitting on the piston so I sanded and polished as much as I could out of it. I should probably get a new piston at some point... In any case, the rubber boot was in good shape, no holes or tears, so I cleaned it up and reinstalled everything with a bit of caliper grease. Long story short, the bleeding went painlessly, and everything seems to be working just fine.

 

[FB71]

it sounds like you have the master cyl out of adjustment - the should be some play between the mc piston and adjusting screw - if the mc is even slightly applied, the compensation and replenish ports are blocked, and you will not be able to get fluid into the caliper, or relieve any pressure from the caliper

 

[torider]

Hey everyone!
Thanks for all the responses and advice, I really appreciate it. My master cylinder and stainless brake lines are only a year old, so I'm assuming that they were ok. I disassembled the caliper today and cleaned it all out. There was some pitting on the piston so I sanded and polished as much as I could out of it. I should probably get a new piston at some point... In any case, the rubber boot was in good shape, no holes or tears, so I cleaned it up and reinstalled everything with a bit of caliper grease. Long story short, the bleeding went painlessly, and everything seems to be working just fine.

That is good to hear. What type of brake fluid did you use? Also make sure to clean the rotor and pad before re-installing the whole thing.

 

[angus67]

did you say you assembled everything with caliper grease? You didn't use it to lube the piston back in did you? only use the same dot brake fluid you intend to use to push the caliper piston back in the bore.
grease is only for the sliders.

 

[Dumbmonkey]

did you say you assembled everything with caliper grease? You didn't use it to lube the piston back in did you? only use the same dot brake fluid you intend to use to push the caliper piston back in the bore.
grease is only for the sliders.

Uh oh!!!
I did use caliper grease on the piston. Looks like I've got to take it part again, how much damage could I have done?

 

[Xmarksthespot]

You probably didn't do any damage, just repeat what you did to clean it up minus the grease on the piston. You were darn close to being right on, life is a learning experience.

 

[angus67]

no harm. now you know. just clean it REAL good this time. make sure every molecule of grease is outta there.

 

[racerdave]

I would take Everything apart and clean with spray brake clean. The mc, the caliper bore seal and piston, and inside the hose's.

 

[Dumbmonkey]

All disassembled, master cylinder, brake lines, caliper bore and piston all cleaned with spray cleaner. Everything seems good now, thank you everyone!!!