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Mick's "Who's ure daddy!?" caliper overhaul
https://www.ausmini.com/forums/viewtopic.php?f=2&t=35255		 Page 1 of 2
Author:  Mick [ Wed Aug 29, 2007 3:13 pm ]
Post subject:  Mick's "Who's ure daddy!?" caliper overhaul
After the problems I had getting the lockheed booster apart, I had another problem crop up with the disc brake calliper.

Now everyone who has rebuilt their callipers has crossed this bridge, I have done so four times so far.
Usually however, it has been on a reasonably fair condition set of callipers and not on a pair of rusted barnicles from below the Devonport high tide mark.

Usually i use a master cylinder attached to a pedal box to remove the calliper piston, but i didn't have this luxury. It takes a lot of fiddling around to jury rig up a pedal box, master cylinder (working) and mount it on something so you can get some leverage into it. Both callipers simply laughed at my crappy amateurish efforts when i tried to cram 120 PSI from a compressor into their blow holes. So I had to try something a little harsher to teach 'em a goddamed lesson about ambition and ability.

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Once again as per the booster, I slipped a grease gun over the bleed nipple fitting from the very same calliper (these are bigger than the drum brake nipples so fit nicely into a standard grease gun) and used the grease gun's pressure to remove the lower piston.

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As the upper piston has a very handy hole behind it to allow me to drift the piston out mechanically, I simply used a crappy G clamp to hold this one in place. Allow this one to fall out and you will be left with no pressure leverage to get the lower piston out.

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It worked so well that it was all over in 5 minutes for the pair of callipers and in pieces ready to be blasted, cleaned, rebuilt and painted.

It beats dealing with the setting up of a master cylinder, bleeding the system up and trying to get the pressure in there. Grease guns put the grease in and don't let it out again, so one pump = one movement of the piston. There's no arguement the piston can put up except "ok mister, I'll move.."

If I had walked in there from out of the blue, grabbed a calliper and a grease gun I would have been in and out in under 10 minutes. Much nicer way of rebuilding a calliper.

***CAVEAT*** Do not use this method on ANY brake component rubber parts you will use again. Mineral based oils and greases swell rubber and will ruin your brakes (potentially on the road!). i will be thouroughly cleaning my callipers out, blasting, degreasing in petrol and then again in metholated spirits (which does not bother brake components) before refitting ALL new seals. This is not for a half job calliper repair.

I thought you might likey likey.

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Author:  Blokeinamoke [ Wed Aug 29, 2007 3:16 pm ]
Post subject: 
was this more effective than using an air compressor?
Author:  Mick [ Wed Aug 29, 2007 3:19 pm ]
Post subject: 
Air compressor won't budge a rusted in piston. have alook at the photos and you can see that one a couple of the pistons they were locked in and dry with no fluid. They simply shrugged off 120 PSI. Usually that may work, though more people have grease guns in their garages than air compressors.
Author:  Blokeinamoke [ Wed Aug 29, 2007 3:20 pm ]
Post subject: 
Mick wrote:
Air compressor won't budge a rusted in piston. have alook at the photos and you can see that one a couple of the pistons they were locked in and dry with no fluid. They simply shrugged off 120 PSI. Usually that may work, though more people have grease guns in their garages than air compressors.


yep I getcha - I hadnt noticed how bad they were :shock: I might try that if I have some bad disk sets
Author:  goodie [ Wed Aug 29, 2007 3:25 pm ]
Post subject: 
Bloody smart character's some of you people eh! Just hope i can remember some of these tricks when the time comes, well done.
Author:  Mick [ Wed Aug 29, 2007 3:25 pm ]
Post subject: 
Blokeinamoke wrote:
Mick wrote:
Air compressor won't budge a rusted in piston. have alook at the photos and you can see that one a couple of the pistons they were locked in and dry with no fluid. They simply shrugged off 120 PSI. Usually that may work, though more people have grease guns in their garages than air compressors.


yep I getcha - I hadnt noticed how bad they were :shock: I might try that if I have some bad disk sets


Yep, I'm just snapping rusted in bolts with gay abandon over here with all the rust. I reckon I could give a tafe course in easyouts by the time I am done. By the same token I'm over pandering to every recalcitrant nut and bolt not up to being unscrewed today. My Supercrap grinder tells em how it's gonna be.
Author:  Matt68 [ Wed Aug 29, 2007 3:49 pm ]
Post subject: 
Please post in the how to section so i remember this when doing my second hand discs in 12 months time!!!!

Looks like a very good way to handle the rusted in pistons!

Well Done

Matt 8) 8)
Author:  lil-ute [ Wed Aug 29, 2007 4:27 pm ]
Post subject:  Re: Mick's "Who's ure daddy!?" caliper overhaul
Mick wrote:


Usually however, it has been on a reasonably fair condition set of callipers and not on a pair of rusted barnicles from below the Devonport high tide mark.


sorry mick but you do know the car was not from Devonport but Calder and Calder does not have a high or low tide its inland
Author:  Mick [ Wed Aug 29, 2007 4:37 pm ]
Post subject:  Re: Mick's "Who's ure daddy!?" caliper overhaul
alsminik wrote:

sorry mick but you do know the car was not from Devonport but Calder and Calder does not have a high or low tide its inland


.....figuratively speaking of course Al...

But there are hight tide marks inside the car on the carpets and the front bulkhead. I am sure it saw some time in a creek or the bottom of a boat ramp. No difference however, I bought the car knowing the extent of the problems.
Author:  AEG163job [ Wed Aug 29, 2007 4:37 pm ]
Post subject: 
next time I do calipers I'll tell 'em in no uncertain terms - don't mess with me or i'll get uncle Mick onto ya" :lol:
Author:  simon k [ Wed Aug 29, 2007 7:58 pm ]
Post subject: 
that's a very very good tip - I had no idea when I pulled mine apart years ago - I don't remember how I got them in the end
Author:  Morris 1100 [ Wed Aug 29, 2007 8:01 pm ]
Post subject: 
I would have dunked the whole lot in vinegar overnight and just pulled the pistons out with my fingers. :wink:
Author:  Austin850 [ Wed Aug 29, 2007 8:15 pm ]
Post subject: 
Morris 1100 wrote:
I would have dunked the whole lot in vinegar overnight and just pulled the pistons out with my fingers. :wink:



You're obviously into chemical warfare. Uncle Mick prefers brute force :)
Author:  9YaTaH [ Wed Aug 29, 2007 8:18 pm ]
Post subject:  Vinegar
Morris 1100 wrote:
I would have dunked the whole lot in vinegar overnight and just pulled the pistons out with my fingers. :wink:


and then...what....lick your fingers :P
Author:  Mick [ Wed Aug 29, 2007 8:24 pm ]
Post subject: 
If we wanted economical ways of going about our business, we wouldn't have V8's now would we... :)

Gimme a hammer and a blow torch and I'll open a can of whoop arse on any stubborn mini bit.

Anyways, I didn't want it open tomorrow, I wanted it open NOW!
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