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#Post#: 49856--------------------------------------------------
What am I missing (brake master cylinder)??
DIR By: onfire
Date: January 26, 2013, 2:09 pm
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Hello again,
I have had a small issue with my brakes since refitting the
whole system a year ago - they were perfect until one of the
rear Britpart wheel cylinders failed after just 80 miles of use
... once I replaced both cylinders and bled the system I found
the brakes made an awful noise when I lightly touched the pedal
(solved by filing the leading and trailing edges of the brake
lining down) and a curious occurence where the brakes clunk with
a little travel on the pedal for the first few minutes / miles
but then a solid pedal and instant brakes from that point
onwards. I had a rear brake binding so filed a little bit off
the metal shoe web to allow it to sit properly inside the drum
(Britpart again Im afraid) and I have had no real problems since
... indeed I did 600 miles in 3 days with no problem before I
filed anything off shoes or linings.
Yesterday I drove 45miles on dual carriageway and motorway and
the brakes gradually pressurised until they seized on and I was
forced to stop ... 3 hours later and they had released and I
could drive her the short distance home.
I am now convinced that the brake system is pressurising ...
probably because the system is not 'relaxing' fully.
From memory the brake pedal is at the right height but it has
always sat tight up against the pedal mounted brake light
switch. I have now unscrewed the switch by half its length and
there is a small amount of travel in the pedl that wasnt there
before. On looking into the pedal box I can see that there is
STILL no play in the master cylinder pushrod (there never has
been, despite the nuts being fully slackened off to the end of
the rod).
Before I replace the master cylinder (which is probably Shitpart
because I didnt know any better when I rebuilt her two years
ago) I wonder if I am missing anything with the setup:
[IMG]
HTML http://i742.photobucket.com/albums/xx63/onfire-photos/IMGP2289_zpsdb9edbcc.jpg[/img]
[IMG]
HTML http://i742.photobucket.com/albums/xx63/onfire-photos/IMGP2289_zpsdb9edbcc.jpg[/img]
[IMG]
HTML http://i742.photobucket.com/albums/xx63/onfire-photos/IMGP2287_zpsa2eab562.jpg[/img]
The clutch master cylinder sits in a pedal box with an adjuster
bolt on the end - this MC sits at a slight downward angle and
has never given me any trouble.
The brake MC is a CV type which sits more-or-less horizontal in
the pedal box (I have just removed the rubber grommet from the
end of the pedal box).
I intend to unscrew the brake switch some more to see if that
releases the pedals full upwards travel ... otherwise I will
change the MC ... but am I missing something else like the pedal
box being the wrong type???
Thank you for your help
... oh, its a Single Line System with 10" SLS brakes on rear
and 11" TLS brakes on the front - the brakes were bled by a
reliable mechanic and the pedal is always firm rather than soft
#Post#: 49857--------------------------------------------------
Re: What am I missing (brake master cylinder)??
DIR By: bob86
Date: January 26, 2013, 2:39 pm
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If the nut on the pushrod is wound right in and it still has on
freeplay sounds like it needs a spacer put between the pedalbox
and the master cylinder. Cant find my parts book but one master
cylinder needs a spacer. My brakes would slowly lock on and
fitting the spacer and setting up the right amount of freeplay
cured it.
#Post#: 49859--------------------------------------------------
Re: What am I missing (brake master cylinder)??
DIR By: bob86
Date: January 26, 2013, 2:44 pm
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Part number is 564944 its for 109 master cylinders
#Post#: 49860--------------------------------------------------
Re: What am I missing (brake master cylinder)??
DIR By: onfire
Date: January 26, 2013, 2:46 pm
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A spacer ... genius! I was wondering if the threaded part of the
pushrod was simply too short and therefore wasnt allowing the
nut to undo enough and therefore giving no freeplay at all
I will look at it again and see if I could use a few washers
over the bolts as an interim solution until I get a spacer -
thanks for the part number
#Post#: 49891--------------------------------------------------
Re: What am I missing (brake master cylinder)??
DIR By: Calum
Date: January 27, 2013, 4:37 am
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I don't know if it matters, but the pedal box you have on the
brake master is for use with the S3 style servo unit. All the
non-servo ones I have seen use the same pedal box as the clutch.
#Post#: 49894--------------------------------------------------
Re: What am I missing (brake master cylinder)??
DIR By: NoelC
Date: January 27, 2013, 4:47 am
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I had the same when I fitted a Lockheed master cylinder to the
109, the pushrod was too long and wasn't releasing the pressure.
I cured it by cutting half an inch or so off the end of the
pushrod with a hacksaw.
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