waynem Posted November 21, 2002 Posted November 21, 2002 If freeing the old cortina calipers from their uprights wasn't enough (the whole arsenal of weapons/tools and brute strength brought to bear..), a piston seems to have seized in its bore. How the b*******y do you free it ? My plan was to join the two halves back together, plug the brake pipe thread with a small nut and try and blow the piston out via the bleed valve using a footpump... Okay! Okay!! I'm desperate..... Really strange thing is, the calipers seem in pretty good nick and still had clean looking copperslip on the pads etc. At least with the rears you can draw them out via the handbrake mechanism.... Argggghhhh!!! Quote
Arm Posted November 21, 2002 Posted November 21, 2002 You are on the right lines, if the rest of the braking system is up and running then connect to the hoses and pump them out with the foot brake. If you are not at this stage then air can also be used, more easily from a compressor but a touch on the dangerous side. BE CAREFUL as when they start to move they will shoot out and spray the remnants of any brake fluid everywhere, maybe cover with a thick blanket before trying this method. Not sure if a foot pump will generate the pressure required Quote
waynem Posted November 21, 2002 Author Posted November 21, 2002 The brake system isn't installed, hence the problem! Sods law isn't it. You can bet your life that if you were changing disks or pads, the b*******s would leap out in a millisecond... I don't have a compressor (although Santa might surprise me) so I'm a bit stuck.. To be honest, patience is wearing out with all this donor gubbins. I'm a gnats chuff away from binning the lot and getting some nice new hubs and calipers from CAT..... The wife won't like that........ Nor the Bank Manager.... Quote
brianm Posted November 21, 2002 Posted November 21, 2002 Fraid compressor/airline aint gonna help, the max pressure you will produce is about100/150 psi. You'll need 10 times that ie the pressure of a hydraulic/brake system to shift them if they are properly siezed. Its no help really but if you connected a hydraulic spreader/ bodyshop type pump to the caliper then you ought to be able to move the piston. Thinking about this if I read your query correctly, you have the caliper split? It would be highly unlikely that the piston is fully retracted in the caliper half as this would suggest that it had siezed with brand new pads in, unlikely for a srappy donor? Try knocking the piston IN wth a hammer to break the bond first. Another tip but never tried it myself, -attach a flexible brake hose to the caliper. Fill with oil. Plug end. Lay caliper/hose on flat surface and smash hose with flat face of wooden mallet. Well I'm told it can work HTH brian. Quote
waynem Posted November 21, 2002 Author Posted November 21, 2002 You might be onto something, Brian.... As as said in my previous post, the calipers do look in good nick, the pads look barely used (hence the fully depressed piston). Copperslip and thick disks and pads suggest the donor Cortina had recently had its brakes serviced.. Wonder if this is when the piston seized ?? The other half isn't quite fully depressed which sort of hints that one side has been wearing more than the other. I'll compare the pads tomorrow. On the good half I can push this piston and see fluid rise and fall in the capillary which joins the halves, so no problems with that one. It may just be slightly stiff, but with nothing to grip onto to........ wait.........and idea is forming......... The dust boot recess in the piston may just offer enough purchase to try and pull it out with some circlip pliers or such like...... All may not be lost!!!!! Just hope I don't knacker the piston in the process..... Quote
Gazza Posted November 21, 2002 Posted November 21, 2002 I think 'we' need to take a step back and think about this.... The pistons are siezed, so the bores and pistons will be damaged on their surfaces (which new seals won't cure). BIN 'EM! New M16 calipers are as cheap-as-chips (£20 from your local motor-factors), so there's no need to compromise a new build with rusty old brakes This isn't the R@bin H@@d site Quote
catflap Posted November 21, 2002 Posted November 21, 2002 I used my paint ball gear Compressed air up to 4500 psi on tap (controleble, and i meen +/ 1 psi controlable with didgital lcd out put pressure regulator In stoke if you need it HEHE edited to say i once did a brake on an old bike and forgot to turn down the pressure, the piston shot out like a bullet, with a loud BANG!!!!!!!! A helthy respect of pressure has become a passion of mine Quote
Gazza Posted November 21, 2002 Posted November 21, 2002 Great! Then he'll have two fecked calipers AND a couple of holes in his garage roof Quote
waynem Posted November 22, 2002 Author Posted November 22, 2002 I haven't got physical yet, so saying they are seized as in rusted to b*******y and beyond hope may be a bit premature. They might just be a bit stubborn... £20 ? Is that a fact ? If so then they may well be filed under `B` very soon... Any particular motor-factor , Gazza ? Not Ford I guess....... Quote
waynem Posted November 22, 2002 Author Posted November 22, 2002 Okay, hows this for a plan... Pull good piston out a bit, fill caliper with some fluid and bleed as much as poss. Use g-clamp to push good piston in, and hopefully stuck piston out..... There will be brake fluid everywhere come bedtime......... Quote
Gazza Posted November 22, 2002 Posted November 22, 2002 Honestly, £20-a-piece. "M16" is the magic phrase. I had one caliper start to drag after a bad winter and when I found out the price for a new one, it becomes pointless trying to repair it. Without machining out the bore and replacing the piston it will always tend to drag or leak. Questionable brakes are the last thing you want at the back of your mind! Any general car parts shop will stock them or at least have them in the next day for you. Sorry for the delay, had to do some work this morning Quote
waynem Posted November 22, 2002 Author Posted November 22, 2002 Best I've found so far is £35+VAT.. I guess that is each..... Still, more numbers to try in the book........ Quote
jeff oakley Posted November 22, 2002 Posted November 22, 2002 Gazza is right, don't mess about with these for £35.00 do you really want to die? If these are stuck there is something wrong with them and no amount of magic cures will bring them back to life. I work in the trade and belive me when you go to the factory and see what goes into getting a caliper recond they are as cheap as chips. Unless you are going for weight the standards will do fine, if you are going for looks and performance as well go to CAT. Quote
JonnyBoy Posted November 24, 2002 Posted November 24, 2002 On first inspection, my m16 caliper pistons were really hard to move. I ended up using my footpump with the inflateable boat attatchment pushed into the fluid hole. 3 12stone pumps and they were out. bores and pistons were in good nick, so new seals (incl. o-ring between 2 halves! and bood as new. well untill they started going rusty again on the surface. Remember to invest in some caliper laquer earlier rather than when the brakes are mounted. The tricky repair is the rear calipers...too much going on in there. I would defineately get new ones of these! new carriers are extortionate though. a good seeing to with a grit blasting gun is woth it (seal the holes though) there you go, more answers than u asked for! Quote
hilux Posted November 25, 2002 Posted November 25, 2002 Go to a garage with a heavy duty grease gun. Believe me it will come out Ensure careful cleaning afterwards though Quote
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