Ross Carter
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| posted on 19/7/15 at 05:55 PM |
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Brake binding
First run out in newly IVA,d and registered MK Indy on Friday identified the following problem after a few miles the brakes started to drag parked up
for 15 mins and car rolls fine set off again and the same thing happens again park up for 10 mins car rolls fine set off again ect
The brake system is as follows
New Sierra duel circuit master cylinder filled with Automec SBF (silicon brake fluid) Clearance on master cylinder push rod
New Sierra front calipers and discs
New Sierra rear handbrake calipers and discs
Copper brake pipes
Would heat in the engine bay cause enough expansion of brake fluid to cause this problem
Any ideas would be welcomed
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daviep
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| posted on 19/7/15 at 06:17 PM |
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Expansion of the fluid due to heat should not cause this, as long as the master cylinder is returning fully then any fluid will be pushed back in to
the reservoir.
Do all wheels drag/lock or just one?
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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adithorp
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| posted on 19/7/15 at 06:38 PM |
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Sounds like your master cylinder push rod doesn't have any free play in it when the brake is released. That means the piston isn't fully
returning and that causes the symptoms as residual pressure isn't released back to the res'. It's a common problem with newly built
cars. Just adjust the pushrod length (at the clevis) so there's a bit of free play.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 19/7/15 at 06:57 PM |
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quote:
Originally posted by Ross Carter
First run out in newly IVA,d and registered MK Indy on Friday identified the following problem after a few miles the brakes started to drag parked up
for 15 mins and car rolls fine set off again and the same thing happens again park up for 10 mins car rolls fine set off again ect
The brake system is as follows
New Sierra duel circuit master cylinder filled with Automec SBF (silicon brake fluid) Clearance on master cylinder push rod
New Sierra front calipers and discs
New Sierra rear handbrake calipers and discs
Copper brake pipes
Would heat in the engine bay cause enough expansion of brake fluid to cause this problem
Any ideas would be welcomed
The problem will be the dual circuit master cylinder piston not returning, I assume you aren't using a servo, the various Sierra master
cylinders were designed to be used with a servo if the pistons are not returning fully by even a fraction of mm it will cause severe binding as the
fluid in the callipers warm up.
If you are using a servo then the plunger that is part of the servo that pushes on the master cylinder piston needs adjusted to give more clearance.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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madteg
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| posted on 19/7/15 at 07:24 PM |
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Check the bleed hole it could be blocked. You will have to remove the reservoir and the hole you are looking for is in the bottom of the recess. It
lets the fluid back into the reservoir when peddle released. I had the same problem when first on the road it was not cooling down but slowly seeping
back in reservoir.
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Ross Carter
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| posted on 20/7/15 at 04:04 PM |
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Thanks for all the reply,s will check everything this evening
As for the cooling theory of mine i thought it was quick and can now understand the reason could be a slow weep back to the master cylinder reservoir
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Ross Carter
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| posted on 8/8/15 at 09:30 AM |
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Further to brake binding problem have checked free play in the pedal and checked for any obstruction or foreign object between the primary piston and
washer/circlip that might have got in during construction, after removing master cylinder fluid reservoir to check fluid return holes for any blockage
i found that the stop pin from the the secondary piston is missing
The binding only effects the font brakes could this be causing the slow return of fluid to the reservoir by the secondary piston being out of
position
The master cylinder is the cast type of 22 mm bore and was brand new
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rusty nuts
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| posted on 8/8/15 at 10:31 AM |
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In a way it's a pity the master cylinder is off, did you try cracking off one of the front bleed nipples when the brakes were binding? If so did
the brakes release? If they did the problem lies with the master cylinder, either not returning or badly adjusted as already suggested. Was the master
cylinder new ? or possibly new/old stock? If the brakes didn't release I would be looking at the calipers or sticking pads
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Ivan
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| posted on 9/8/15 at 07:40 AM |
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I had this problem with my Cobra years back - turned out my brake hoses had rotted inside and swollen shut due to wrong grade silicon brake fluid. The
hoses looked perfect from the outside.
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