Series 3 brake issue

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Johnnyg131313

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  • Name: John Graham
Series 3 brake issue
« on: August 09, 2021, 08:17:10 AM »
Hi. I have a 1971 Series 3 with a brake issue which I would appreciate some advice on please.

I've replaced everything in the brake state. Which is single.line and CV master cylinder. The brakes have been bled a number of times and seem to be free of air. All drums are adjusted.

The problem I believe, is with the adjustment on the master cylinder which should have 1.5mm play. I'm not clear how to achieve the 1.5mm play.

There is a locknut at the engine side of the pedal and one on the bulkhead side. Screwing up the nut on
 the bulkhead side locks the brakes on with a hard pedal whereas letting off the same lockout the pedal will pump up and then on the next press of the pedal, it goes to the floor. Bleeding again finds no air in the system.

How does one adjust the master cylinder to achieve the 1.5mm play? 

Many thanks in advance.

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discoverypete

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  • Name: Peter Williamson
Re: Series 3 brake issue
« Reply #1 on: August 09, 2021, 07:38:45 PM »
Are these the nuts you are adjusting?
https://littlegreenlandy.files.wordpress.com/2020/04/ynvr2hzszehql7jtmbhwq.jpg?w=768

                 Pete.

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Johnnyg131313

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  • Name: John Graham
Re: Series 3 brake issue
« Reply #2 on: August 09, 2021, 10:02:53 PM »
Yes.

The nut on the bulkhead side of the pedal pivot either locks up the wheels if adjusted owards the engine, or if adjusted towards the bulkhead results in a brake being there by pumping the pedal, but then goes to the floor a moment or two later.

If I adjust the nut on the bulkhead side until the brakes lock and the loosen it off, I can hear the brakes releasing due to the pressure being released.

It's a new CV brake cylinder from Paddocks.


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discoverypete

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  • Name: Peter Williamson
Re: Series 3 brake issue
« Reply #3 on: August 10, 2021, 04:35:13 PM »
It does sound like you are describing a faulty cylinder. Give paddocks a phone and have chat, I have always found them helpful and they may have a trick up their sleeve.

                            Pete.

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Johnnyg131313

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  • Name: John Graham
Re: Series 3 brake issue
« Reply #4 on: August 11, 2021, 08:50:48 AM »
Thanks DiscoveryPete.

This is the second new master cylinder I've purchased as I had presumed the last one had as issue due to excessive pumping of the pedal during bleeding activity.

It's very frustrating as everything on the braking system is new yet I cant achieve a pedal.

Is there guidance on how to adjust the master cylinder piston nuts at the brake pedal pinion?

The Haynes manual just says adjust it to 1.5mm, but not how to do that. Which nut is to be adjusted and which to lock the adjustment in position?

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discoverypete

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  • Name: Peter Williamson
Re: Series 3 brake issue
« Reply #5 on: August 11, 2021, 10:13:46 PM »
There is a picture but not a lot of instruction. I will scan it tomorrow and see if I can put it on here.

             Pete.

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discoverypete

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Re: Series 3 brake issue
« Reply #6 on: August 12, 2021, 10:52:36 AM »
Not very good because the manual is so thick.

I hope this helps.

             Pete.

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Johnnyg131313

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Re: Series 3 brake issue
« Reply #7 on: August 12, 2021, 08:10:51 PM »
Thanks Pete.

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Navigator

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  • Name: Stuart Clink
Re: Series 3 brake issue
« Reply #8 on: August 14, 2021, 09:26:37 AM »
No air = fluid passing a seal in master cylinder.   Is it possible you have to two pipes on the master cylinder connected to the opposite ports?
Navigator          GM1VBE

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Johnnyg131313

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Re: Series 3 brake issue
« Reply #9 on: August 15, 2021, 12:17:28 AM »
Thanks very much for the assistance.
On the master cylinder there are two pile connections: one to the rear of the cylinder at bulkhead and one to the front of the cylinder. The the pipe from the fluid reservoir connects into the bulkhead end and the feed to the brakes is at the front of the cylinder.