Quote:
Originally Posted by Steve 940
Yay, success!!!
Dave's first suggestion of pressing in, worked first time👍👍
After pressing piston in a few mmm, tried my little 25 ltr 8 bar air compressor using the blow gun, with rubber protecting hose union threads, piston came out a dream.
Oh, top tip, I had taken precaution of using reducing thicknesses of scrap wood to protect the piston as I was aware it may come out with some force. Certainly did, you wouldn't want fingers in the way!!!!
Also just need to be a bit careful using this method, as the old fluid in the caliper did squirt out as I couldn't get a 100% air tight seal, perhaps make sure goggles on.
Piston looks in good shape, caliper now back in electrolysis tank to see what we've got. Not sure if saveable, as it did feel as though there was a slight ridge around 10mm up from the bottom of the bore, may be just general crud🤞
Any tips for removing the seal without damaging the caliper?? Also any tips on assessing caliper for wear etc once I get it out of the electrolysis tank?
Cheers
Steve
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If you use a cotton polishing drum in a drill and some Halfords rubbing compound on it, you can polish and remove the ridge in the piston bore. From everything that's gone so far, i'd suggest the ridge is simply dirt that has formed round the forward edge of the seal and until you moved the piston in there wasn't enough momentum behind the piston when trying to eject it with compressed air.
https://www.halfords.com/motoring/pa...in%20a%20jiffy.
I believe (although not 100% sure) it's what is known as a "diminishing abrasive" - in other words it starts off coarse and as it's used, the particles reduce in size so the longer it's used, the finer the finish. Obviously there's a point where it's removed enough plating that if any more is removed there will be no plating but you'll have achieved a near-mirror finish long before then unless corrosion has pitted the piston and/or caliper bore.
Don't forget to wash any excess compound out once done, any remaining abrasive will wreak havoc with new seals!
I normally use acetone or IPA as both are good degreasers/cleaners/solvents.
I'd add the piston to the electrolysis tank as well, it probably didn't get much first time round unless you deliberately added a wire link to the piston so it became an electrode. You may be pleasantly surprised at the result of adding the piston!
Also don't forget to bake the caliper and piston in the oven for an hour or so to aid removal of the hydrogen from them to avoid hydrogen embrittlement. Most things you can get away with and just let them naturally degas before painting with no long term effects from the hydrogen but with suspension, brake and steering components, i'd definitely give them an hour or so at ~100C to help get the hydrogen out quickly.
Once it's all clean and dry with any remaining dirt removed, you can assess the condition and go from there.
