Daddylonglegs
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| posted on 7/4/13 at 07:32 AM |
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Brakes, Again!!
Went out for a shakedown drive yesterday after a looooong winter off, mainly to test the brakes after all my faffing around changing over to a Fiat
MC.
Got about 1m down the road and the pedal started getting harder with each press and the car was being held back. I assumed brakes binding so stopped
for a minute to make sure they weren't overheated and came home. Only just made it as the nearside front was locked on! pedal by now was solid,
so I cracked off the caliper bleed nipple and the brakes came off immediately, so my guess is the fluid is not returning to the reservoir.
I tried fitting a remote reservoir to the MC but just cannot make it fit high enough to keep a good feed of fluid to the MC, so I used the original
Sierra reservoir and used some short lengths of tubing to connect it to the MC. The trouble is, I think what is happening is that the tubing I have
used is so far down the seals in the MC that it is actually blocking off the fluid holes enough to prevent the fluid returning to the reservoir.
The reason I had to extend the reservoir up from the MC is because the MC outlets are on to and not on the sides so I cannot fit the reservoir
directly into the MC.
What I need to do now is find some sort of remote reservoir that is short enough to fit above the MC and can be connected using the adaptors for
tubing.
Has anyone got any recommendations for CHEAP reservoirs either new or from a scrappy?
Hope all the above makes sense? 
It looks like the Midget is winning at the moment......
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rusty nuts
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| posted on 7/4/13 at 07:36 AM |
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Sound very much like there is not enough slack in the master cylinder push rod to me,
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Ivan
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| posted on 7/4/13 at 07:50 AM |
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I had a similar problem with my Cobra some time back - turned out one of the rubber brake lines had swollen shut. Most probably not your problem but
worth a look.
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mark chandler
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| posted on 7/4/13 at 08:00 AM |
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quote:
Originally posted by rusty nuts
Sound very much like there is not enough slack in the master cylinder push rod to me,
What he said, the plunger in the master cylinder is not returning far enough to reveal the hole going back to the reservoir, you now have created a
pump.
Simple to resolve shortern the pushrod to the pedal and make sure the return spring on the pedal is good.
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britishtrident
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| posted on 7/4/13 at 08:07 AM |
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As above master cylinder push rod too long not allowing the piston in the mastercylinder pushrod to come fully back causing fluid lock.
If the piston is even 1mm off the end stop will cause the recuperating port to be closed off and cause fluid lock.
[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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whitestu
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| posted on 7/4/13 at 09:04 AM |
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quote:
As above master cylinder push rod too long not allowing the piston in the mastercylinder pushrod to come fully back causing fluid lock.
If the piston is even 1mm off the end stop will cause the recuperating port to be closed off and cause fluid lock.
I had exactly the same issue with my Fiat MC. It's tempting to tighten the push rod up to get a firmer pedal, as the pedal feels so much softer
than the Sierra MC.
Back it off a bit and it should be fine.
Stu
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David Jenkins
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| posted on 7/4/13 at 09:37 AM |
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If it happens again, try hooking your toe under the brake pedal and pulling back (if it's a top-pivot pedal, of course!). If the brakes free
off then it's the master cylinder push rod not returning fully, as suggested above.
I used all of the springs that came with my Escort pedals, and the one that pulls the brake pedal back to its rest position is massive!
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Daddylonglegs
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| posted on 7/4/13 at 08:51 PM |
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Thanks for all the input guys
I will try the pedal trick and see if it does need a shorter pushrod, but I think there is sufficient play in the rod-to-piston.
I have put a piccy below to try and explain better what I meant about the modification to extend the reservoir up from the MC and the possibility of
the pipe blocking the holes off.
 
Still think I will be looking at replacing the reservoir, but I hope you guys are right 
It looks like the Midget is winning at the moment......
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johnemms
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| posted on 7/4/13 at 09:33 PM |
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Rod too long.. happened to me on first test drive..
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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