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what are my chances of changing the brake pads in the fiesta without any problems, there not far off the limit now so they need changing will it be easy to push the brake pistons back into the calipres without too much trouble as i dont have a wind back tool i heard you can do it with a c-clamp but i cant see it fitting the gap, any tips welcome ..thanks
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i use water pump pliers they cost about £5.00 if you open the bleed nipple and push the piston back this method will be fine, clean all up with a wire brush especially were the pads sit and use copper slip on the backs everything ok.
i run in/ bed in pads about 300mls good luck.
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Depends on the shape of the clamp;if the ends are reasonably square it will work-if a car is not fitted with ABS the pistons should push straight back without opening the bleed valve-it can't affect the seals,it will go straight back into the resevoir but make sure that does not overflow.
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You can lever the pistons back in with a big screwdriver, but leave the old pads in when you do it so that you damage them rather than misaligning the pistons.
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thanks for the tips, il see if the chap on ebay has still got the pads and disks kits for sale bout £15.00 i think
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Buy your brakes from a decent supplier please. They are no dearer at a good motorist shop or motor factor and they are your safetty ! Mine too if you cant stop and im in front of you !
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thanks yorkiebar advice taken on board
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No point in replacing the pads unless the discs are within spec and flat and shiny.
Don't force old fluid back up into the master cylinder, it's a sure way of damaging its seals too and then needing a complete system overhaul and bleeding. Release the surplus fluid out of the bleed nipple. If it's at all dirty flush some new stuff through.
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To expand on that,if the discs have a lip and/or are scored -replace.If in doubt-replace.Probably worth replacing the fluid if it not fairly new,it is hygroscopic(absorbs water).Re copper based grease,use this on the backs of pads where contact is made,plus sliding contact points-but-only a thin smear-excess can be dangerous.
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Cliff
Please don't take this as a personal comment. It's just that I've so often seen it stated that it's damaging to push fluid back to the master cylinder, and that this might cause the master cylinder seals to 'flip' that I've finally decided to make a comment! I simply don't understand this. The seals are designed to handle significant pressure when the brakes are applied and do this without 'flipping', so why returning fluid under very little pressure would flip them I don't know. It's also the case that the reservoir above the master cylinder has a clear connection to the brake system to allow it to keep it full as pads wear. So, it's difficult to see how any significant pressure is built up when pistons are pushed back. I've never had any problems retracting pistons and pushing the fluid back to the master cylinder since I've worked on cars for longer than I care to mention. However, I've heard it so often said that seal failure can occur, I guess there must be something in it. My theory is that it may be that the problems are bought on by worn seals and/or corroded master cylinders giving up when the system is given long pedal strokes to push the pads back into contact with the discs, and has absolutely nothing to do with the fluid return itself. I'd be delighted to hear of any other theories.
JS
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I didn't mean the seal flip theory - I'm not so sure about that myself.
But if the fluid hasn't been changed for a long time and there is rusty debris accumulated in the caliper chambers, then pressing the pistons right back to accept new pads pumps this muck right back to the master cylinder. There is then a risk that it will damage the seals or bores, and of course it is also free to be dispersed back down all the other brake lines.
It is also true as you say that long pedal strokes, as in bleeding or taking up at the pistons, can bring about failure of the master cylinder seals, for the same reason.
I have experienced the latter failure, and know of many other cases where it has happened. The first is perhaps only a theoretical risk as you say.
The safe thing is perhaps to pressure-bleed off some fluid to start with, and if it is dirty, continue (with refilling) until it runs clear.
Then the pistons can be pushed in knowing that any dirt has already been expelled.
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Cliff
Yes, completely agree about the need to ensure the fluid is clean, and ejecting it via the bleed nipple for a 'cleanliness check' isn't a bad idea. Perhaps not so much a problem these days when there is more awareness of need for regular fluid changes. Have to say back in the days when no-one ever changed brake fluid I've seen some incredibly dirty fluid bled out of cars when brake cylinders were changed!
JS
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The only way master cylinder seals could be damaged is if you have the pedal down.Fluid going back from the slave cylinder will go straight to the fluid reservoir;this supply will only be shut off when you put your foot on the pedal and the seals are moved forward to pressurize the system.
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Cliff, John,
I know what you mean about the problem with the mechanism for seal flipping - I agree that the fluid *should* go back into the reservoir.
However, while I worked in the Vauxhall garage, we had two cars which did this. In both cases, we decided that it was safest to rebuild the master cylinder with a new seal kit. Now, these were cars being worked on by colleagues, so, I don't know the "full" story. It is possible that the pedals were sticking a bit, and the reservoir port wasn't opening, and it is also possible that the caliper pistons were forced back quickly and violently - I tend to go fairly gently, and apply gentle pressure with water pump pliers, and let the pistons return at their own speed.
I agree with the view about avoiding forcing dirty fluid back upstream - particulalry if you are forcing it into an ABS unit.
Number_Cruncher
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If the reservoir port is blocked by sticky piston/pedals your master cylinder needs a clean and rebuild anyway.
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>>If the reservoir port is blocked by sticky piston/pedals your master cylinder needs a clean and rebuild anyway.
Indeed!
Number_Cruncher
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