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 Post subject: brakes again 1970 CS
PostPosted: Tue Jan 08, 2019 3:28 pm 
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848cc
848cc

Joined: Mon Dec 19, 2016 8:38 pm
Posts: 433
Still have the problem with brakes ,everything is new or reconditioned. Now ,when you push the pedal a few times the pedal goes hard and the front disc brakes lock, after a few minutes they release, this is without the engine going. A good mechanic has told me when they resleave the master they partially block off the fluid hole in the master cylinder. I am now trying to borrow a mk 2 master cylinder so I can check if this is the problem. I live in the Newcastle area if anyone has got one that I can borrow. Any ideas ????
TY Allen


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 5:19 am 
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998cc
998cc

Joined: Mon Jan 12, 2015 10:59 pm
Posts: 693
Location: Holt ACT
p7676 wrote:
Still have the problem with brakes ,everything is new or reconditioned. Now ,when you push the pedal a few times the pedal goes hard and the front disc brakes lock, after a few minutes they release, this is without the engine going. A good mechanic has told me when they resleave the master they partially block off the fluid hole in the master cylinder. I am now trying to borrow a mk 2 master cylinder so I can check if this is the problem. I live in the Newcastle area if anyone has got one that I can borrow. Any ideas ????
TY Allen


Did you have the master cylinder re-sleeved? If so, why not quiz the people who did the job what they did? My understanding is that the tank has to be removed to able the hole to be re-drilled.


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 8:04 am 
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848cc
848cc

Joined: Mon Dec 19, 2016 8:38 pm
Posts: 433
the MC was resleeved


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 11:17 am 
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998cc
998cc

Joined: Mon Jan 12, 2015 10:59 pm
Posts: 693
Location: Holt ACT
p7676 wrote:
the MC was resleeved


Was the hole re-drilled through the sleeve?


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 1:09 pm 
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Yay For Hay!
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Joined: Wed Sep 08, 2004 9:27 pm
Posts: 15266
Location: Wodonga - Vic/NSW border
its easy to check... but check your private messages Allen

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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 5:13 pm 
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998cc
998cc

Joined: Wed Sep 22, 2004 5:46 pm
Posts: 692
Location: Melbourne
Check the residual pressure valve in the master cylinder.
I had a problem recently with a MK1 master cylinder where some rust flakes from inside the tank were trapped in the valve and it wouldn't let fluid back into the master cylinder and the brakes wouldn't release properly. I currently have a plastic tank MK2 m/c fitted because that's what I had on the shelf.
I know its not the same type of master cylinder but the plastic tank type should still have the residual pressure valve fitted. If there is no residual pressure in the brake lines then you can get air sucked into the system through the drum brake wheel cylinders. The residual pressure keeps the wheel cylinder cups expanded. The valve is essential for any car that has drums or disc/drum combination brakes.
If you have a split system master cylinder you still need the valve in the line to the drum brakes. It may be the cause of your brake booster problem from your earlier post.

RonR

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Last edited by miniron on Thu Jan 10, 2019 9:16 pm, edited 1 time in total.

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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 7:26 pm 
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1098cc
1098cc

Joined: Mon Nov 06, 2006 8:54 pm
Posts: 1581
Location: Hunter NSW
Are you using plastic m/c or tin tank?


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 8:32 pm 
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848cc
848cc

Joined: Mon Dec 19, 2016 8:38 pm
Posts: 433
plastic tank, is miniron correct? I was told by the brake place they do not have a residual valve when there is disc brakes.
Allen 1970 mk2 c.s


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 9:48 pm 
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1275cc
1275cc
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Joined: Fri May 02, 2008 3:07 pm
Posts: 4069
Location: Bundy
p7676 wrote:
plastic tank, is miniron correct? I was told by the brake place they do not have a residual valve when there is disc brakes.
Allen 1970 mk2 c.s


The manuals calls it a non return valve to prevent a loss of fluid when parked on an incline. But it is more like a slow return valve or a residual pressure valve.

It does help to keep the wheel cylinder seals expanded and it does help to keep air from being sucked in and it also helps when pumping up the brakes.

I can only find the tin type reference at the moment.

Attachment:
Brake Master Cylinder non return valve.jpg


Attachment:
Brake Master Cylinder Parts.jpg


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 Post subject: Re: brakes again 1970 CS
PostPosted: Wed Jan 09, 2019 10:34 pm 
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998cc
998cc

Joined: Wed Sep 22, 2004 5:46 pm
Posts: 692
Location: Melbourne
My understanding is that brake drums are not always perfectly round and any ovality can cause the brake shoes to move the wheel cylinder pistons slightly back and forward and in the process air can be drawn into the wheel cylinder by the movement if you don't have a residual pressure valve. The valve only maintains a few PSI in the brake lines.
It may well be to prevent fluid flowing back to the master cylinder but only if the car is parked on a steep incline with the front pointing downhill and then only if the rear wheels were higher than the master cylinder, but I am still willing to learn.
If you don't learn something new every day you are not trying.
Disc brakes don't need the valve as they have a different type of seal which doesn't rely on the wheel cylinder cups being expanded slightly.
There are at least 2 types of residual pressure valves, one is a rubber type and the other is a white plastic type with a circular spring steel strip around it.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required


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 Post subject: Re: brakes again 1970 CS
PostPosted: Thu Jan 10, 2019 5:53 am 
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1360cc
1360cc
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Joined: Sun Apr 11, 2004 11:32 am
Posts: 11503
Location: Sthrn HiLoLands, NSW, Australia
I really think that you should find another brake specialist...preferably Mini savvy...there is something that they haven't picked up and/or are not picking up.

Ask your local Mini Car Club for recommendations...cut your loses and avoid a failure or expensive accident :idea:

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 Post subject: Re: brakes again 1970 CS
PostPosted: Thu Jan 10, 2019 8:16 am 
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848cc
848cc

Joined: Mon Dec 19, 2016 8:38 pm
Posts: 433
does anyone know a brake place that may do minis ?I seem to be going around in circles, they may have an answer otherwise I will buy another master cylinder, the current mc cost me $175 for the reco.
TY Allen


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 Post subject: Re: brakes again 1970 CS
PostPosted: Thu Jan 10, 2019 8:23 am 
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998cc
998cc

Joined: Wed Sep 30, 2015 9:38 am
Posts: 626
Location: Brandy Hill, NSW
There is a brake place at East Maitland, have you tried them?


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 Post subject: Re: brakes again 1970 CS
PostPosted: Thu Jan 10, 2019 1:09 pm 
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Yay For Hay!
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Joined: Wed Sep 08, 2004 9:27 pm
Posts: 15266
Location: Wodonga - Vic/NSW border
p7676 wrote:
does anyone know a brake place that may do minis ?I seem to be going around in circles, they may have an answer otherwise I will buy another master cylinder, the current mc cost me $175 for the reco.
TY Allen


The old bloke at my local brake place has been in business since the beginning of time, he knows all of the old stuff. I guess my offer to you works in the opposite direction too, send it down to me and I can get them to sort it and I'll send it back

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 Post subject: Re: brakes again 1970 CS
PostPosted: Thu Jan 10, 2019 1:13 pm 
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1275cc
1275cc
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Joined: Wed Oct 03, 2007 9:04 pm
Posts: 5285
Location: Melbourne, VIC
simon k wrote:
The old bloke at my local brake place has been in business since the beginning of time ...

He would've resoled Fred Flintstones shoes a few times then?

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