Wells
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| posted on 31/1/10 at 11:06 PM |
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Bleeding Brakes
Iam having a nightmare trying to bleed my brakes! Ever since I replaced my rear calipers I have never been able to get a firm pedal like I had before.
Does any body have any ideas I could try?
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austin man
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| posted on 31/1/10 at 11:15 PM |
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are you using sierra rear disscs and callipers ?? if so I think you have to tilt the calliper backwards when bleeding, something to do with the bleed
nipple being too low, MK indy's have this problem when disc's ar fitted
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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Wells
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| posted on 31/1/10 at 11:27 PM |
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Yeh it sierra rear discs and calipers. I have tryed this but still no joy. I dont know whats going on!
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blakep82
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| posted on 31/1/10 at 11:33 PM |
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hmm, which way up should they be? got a feeling mine might be on the wrong way
________________________
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Wells
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| posted on 31/1/10 at 11:38 PM |
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What do you mean when you say the wrong way?
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jack_t
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| posted on 31/1/10 at 11:52 PM |
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you might have the same problem as i did on my indy
what you have to do it unbolt the caliper and take the disc of and turn the caliper upside down so the bleed nipple is totally vertical pointing
upwards
remember to put the disc between the pads when the caliper is in this position and you are bleeding as if you dont u will have to rewind the
caliper
next time i am home i am going to make a picture tutorial to deal with this occurrent problem
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blakep82
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| posted on 31/1/10 at 11:55 PM |
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well, i've got mine on a atlas axle. i think mine are on the wrong sides, and by the looks of things, on a sierra they were mounted at the top of
the 'axle' mine are mounted to the rear, with the handbrake cable entering from underneath
think you might need to hold them this way to get them to bleed properly
heres how mine are
 
Description
[Edited on 31/1/10 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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speed8
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| posted on 1/2/10 at 06:39 AM |
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Are you using an EZ Bleed? I only ask as I had real trouble doing it this way and ended up getting my missus working the pedal whilst I bled it the
old fashioned way. It worked a treat like this and pedal is solid.
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cd.thomson
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| posted on 1/2/10 at 09:12 AM |
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hi blake, no i think you've got it right.
you want the bleed nipples at the top, otherwise you'll end up with a pocket of air in the top of the caliper.
Craig
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blakep82
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| posted on 1/2/10 at 12:25 PM |
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quote:
Originally posted by cd.thomson
hi blake, no i think you've got it right.
you want the bleed nipples at the top, otherwise you'll end up with a pocket of air in the top of the caliper.
if you look at the way they are on the sierra though, the pipe comes in below the bleed screw. i've got mine both level. will just need moving
around when i come to bleed them, thats all 
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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antonio
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| posted on 1/2/10 at 01:24 PM |
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pretty sure you have the same i had prior i dicovered my front callipers were not square to the disk (thank you british trident)
callipers were too flixible, and drain back cause a spongy pedal.
i had to shimed/"grind", my calliper mounts to get them right.
ally bulkhead on MNR are very bad IMHO as the are way too flexible.i also welded a steel plate where master cylinders are fixed.my english sucks, so
here is what british trident advise me to do, i should be easy to understand in his words:
You really have to make 100% sure the caliper is presenting the pad parallel to the disk in in all axes if not you will get lost motion at the pedal.
It takes only a tiny amount of movement at the caliper to result in excessive pedal movement.
After market calipers are very bad for this because they do not mount straight on to the standard brackets, longer multi piston calipers make the
effect much worse.
If the caliper is to true to the disk every time the pedal is pressed the caliper bracket has to bend elastically (ie it acts as a spring) when the
pedal is released the fluid is slowly forced back to the master cylinder.
Because of very clever design of the main rubber hydraulic seals in caliper the It takes a lot of pressure difference to push back the pistons in a
caliper, the difference in pressure of having the calipers 100mm or so higher than the fluid level in the resevoir isn't anywhere near enough to
over come the static friction.
the seals is the caliper are designed to have a friction characteristic.
If you get lost motion on the first pump of a disk brake system if the mater cylinder is OK it it is a sure sign some mechanical component is flexing.
(1) Check all the pistons in the caliper are moving freely.
(2) Check the caliper body is set a square as humanly possible to the brake disk.
(3) Check for flexing of the caliper body under pressure using a dial gauge --- some alloy multi pot "racing" calipers are no where near
rigid enough.
(4) Check the pedal box and its mountings for flexing using a dial gauge.
[Edited on 1/2/10 by antonio]
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