smart51
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| posted on 26/2/06 at 07:05 PM |
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sierra front caliper problem
I went out in my car yesterday and after a few miles started to smell hot brakes. I pulled in at the next petrol station and sure enough, one of the
brakes was scalding hot.
I looked at the caliper today. The wheel would turn but then when the brake was applied and released it beacame difficult to turn.
I have taken the caliper off and it looks OK but when I came to put it back on, the piston won't move back far enough to get the pads and disc
back in.
What is wrong with my caliper?
How do I get the piston to move back in?
The rear caliper's pistons have notches in them so that you can turn them back in.
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RazMan
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| posted on 26/2/06 at 07:08 PM |
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Simply put - you have got a seized caliper 
You might be able to refurb it with a kit from a motor factors (or maybe Ford) but more than likely the pistons will be scored and you are looking at
a new caliper.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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smart51
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| posted on 26/2/06 at 07:16 PM |
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It has only done 1400 miles since it was fitted. It had been stipped and painted when I bought it and I cleaned and reassembled it with new piston
seals and dust seals. Is "sealed buy a new one" the only possible cause?
It works well enough in that I locked up that wheel on the way home so its not totaly nackered.
How do I get the piston out so that I can inspect it?
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MkIndy7
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| posted on 26/2/06 at 07:29 PM |
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Sometimes the outer dust seal comes slightly loose if the groove it fits in wasn't cleaned properly or has got some paint in it.
Just pop the caliper all the way out, and you'll probably see the tinyest bit of rust thats causing it.
To get it out the easiest way is to take it off and disconect the brake pipe flexi, and then very very very! carefully using a foot pump, hold the air
hose upto where the flexi came out of and pump gently, the piston should slowly come out.
Then give it a wipe with some brake cleaner or brasso etc and clean out the dust seal groove and pop it all back making sure the seal goes back on
correctly.
I had exactly the same thing on my Fiesta a few months ago after refurbing and painting the calipers.
[Edited on 26/2/06 by MkIndy7]
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britishtrident
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| posted on 26/2/06 at 07:34 PM |
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First check it isn't a master cylinder problem -- yes in theory it shouldn't just effect one cylinder but that is theory ---- to check
this put a nip clamp the flexy hose (you can only do this with proper brake hoses not braided types) open the nipple a turn and a half and try
pushing the piston back.
The reasons why rear calipers have notches on the pistons is to turn back the mechanical self adjuster -- obviously front calips don't have
a hand brake so no self adjuster required.
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indykid
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| posted on 26/2/06 at 07:34 PM |
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and just to be certain, there is free play on the push rod(s) for the master cylinder isn't there? if the mc piston can't return fully, it
won't allow fluid to be pushed back.
seems to be a recurring theme of late. a quick search should bring up everything you could possibly need to know!
tom
beat me to it BT. do what BT says, he's not usually wrong.
[Edited on 26/2/06 by indykid]
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britishtrident
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| posted on 26/2/06 at 07:36 PM |
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Usual warning about dangers of using compressed air.
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givemethebighammer
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| posted on 26/2/06 at 09:04 PM |
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quote:
Originally posted by MkIndy7
To get it out the easiest way is to take it off and disconect the brake pipe flexi, and then very very very! carefully using a foot pump, hold the air
hose upto where the flexi came out of and pump gently, the piston should slowly come out.
[Edited on 26/2/06 by MkIndy7]
Put a piece of wood on the caliper and keep your fingers out of the way. The piston may not come out very slowly, in fact quite the opposite. Worth
wearing goggles too as brake fluid in the eyes won't do them much good. Also do it away from anything you don't want brake fluid on (i.e
the tin top). Any fluid left in the caliper may spray out, it's only likely to be a small amount but enough to damage eyes and paintwork.
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MkIndy7
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| posted on 26/2/06 at 10:14 PM |
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yup very wise words of warning, should have been a little bit more specific myself.
Its usually a crap seal and not a very good foot pump that we use to get them out!
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smart51
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| posted on 26/2/06 at 10:20 PM |
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thanks guys. The outer dust seal had partly come out of the groove in the caliper. I took out and cleaned the piston. No rust other than watery rust
from where the seal had come away. The brake fluid seal had protected the main part of the piston. I've put it all back together and it seems
to work. The bleed screw had siezed and removing it has rounded the hexagon bit. A new one from Ford and I should be back on the road. thanks
again.
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