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 Post subject: Lost brakes
PostPosted: Wed Apr 11, 2018 5:24 pm 
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848cc
848cc

Joined: Mon Mar 06, 2017 7:30 pm
Posts: 4
Hi, looking for advice. 67 Cooper S, driving home and noticed the braking efficiency had dropped off heaps. I really had to stand on the pedal to stop. The pedal also went down really low.
I checked for obvious leaks, nil. There was still fluid in the tank. When I press the brake pedal, there is a hissing noise which I think is coming from the brake booster. Does it sound as if I need a new booster or is there something else I should check first? Thanks in advance.

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 Post subject: Re: Lost brakes
PostPosted: Wed Apr 11, 2018 5:50 pm 
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998cc
998cc

Joined: Fri Apr 01, 2011 8:33 pm
Posts: 1146
A "new" booster is a bit OTT... Its just the diaphragm that probably needs replacing (BTDT) ...although you may as well refurb the rest of it while you're there...(depending on what kit you can find:)

Cheers, Ian


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 Post subject: Re: Lost brakes
PostPosted: Wed Apr 11, 2018 8:18 pm 
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Yay For Hay!
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Joined: Wed Sep 08, 2004 9:27 pm
Posts: 15861
Location: Wodonga - Vic/NSW border
If the booster has failed, it's not an issue to drive the car without it, the brakes work just as well but you've gotta push the pedal a bit harder. Hydroboost in Echuca can recondition it for you

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 Post subject: Re: Lost brakes
PostPosted: Thu Apr 12, 2018 7:29 pm 
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998cc
998cc

Joined: Fri Aug 30, 2013 8:59 pm
Posts: 1029
Location: Western Sydney
Doesn't the booster just reduce pedal force required.
The pedal going lower must surely be a hydraulic issue ?

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 Post subject: Re: Lost brakes
PostPosted: Fri Apr 13, 2018 7:51 am 
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1360cc
1360cc
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Joined: Sun Apr 11, 2004 11:32 am
Posts: 12390
Location: Sthrn HiLoLands, NSW, Australia
Phil 850 wrote:
Doesn't the booster just reduce pedal force required.
The pedal going lower must surely be a hydraulic issue ?


Yes and No...if the booster is passing fluid through the diaphragm or elsewhere...the pedal pressure will vary and your fluid level at the master will drop. Symptom can be white smoke out the exhaust.

If you can stop ("lock") the front wheels from rotating with un-boosted brakes...then that is the best you can hope for...

VH40 = 3:1 mechanical advantage
VH44 = 2:1 mechanical advantage

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 Post subject: Re: Lost brakes
PostPosted: Mon Apr 16, 2018 7:27 am 
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1275cc
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Joined: Thu Aug 31, 2006 7:56 pm
Posts: 2651
Location: Muswellbrook -- NSW
I agree with the booster diagnosis , as for the pedal height , how long since the rears have been adjusted ?


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