MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

'69 brake master cylinder Trap valve question
Posted by: limey222
Date: September 25, 2015 10:01PM

I have question about my non-servo brake master cylinder on my 1969 MGB.

The rear connection has a trap valve and spring installed but the front connection doesn't , is one missing or is this normal?

Also I believe that my trap and spring were installed backwards, in other words, the plastic trap was installed first with the spring on the outside. I noticed that it should be the reverse according to the exploded view in the Moss catalog. What would the effect be on the brakes if they were installed in the wrong order?


88v8
Ivor Duarte
Gloucestershire UK
(719 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: '69 brake master cylinder Trap valve question
Posted by: 88v8
Date: September 26, 2015 05:19AM

As I understand it, purpose of the valve is to keep some residual pressure in the system so as to minimise pedal travel, even if the rear drum brakes are not in good adjustment.
There wouldn't be one on the front as the calipers have no pulloff springs, although there could be a valve if it were a car with drums all round.
Sadly, I don't think this has any relationship to your problem. With the valve reversed, the brakes should work normally although perhaps with a longer pedal.
However it does nothing to increase confidence in the product.

Ivor


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: '69 brake master cylinder Trap valve question
Posted by: limey222
Date: September 26, 2015 11:20AM

Ivor,
Thanks for your response. I asked the question because as part of my quest to fix my front brake problem I received a new master cylinder yesterday and installed it last night. I'm pretty certain that I have installed the trap valve and spring in backwards hence my question. I'll rectify that and then bleed the brakes today and see if i has solved the problem. If it doesn't then the only thing left is the calipers and I don't see how the same problem could occur simultaneously on both sides.


Nexxussian
Erik Johnson
Alaska
(62 posts)

Registered:
04/20/2015 10:32PM

Main British Car:
1974, MGB, Citroen Color Rover V8

Re: '69 brake master cylinder Trap valve question
Posted by: Nexxussian
Date: September 26, 2015 03:27PM

Good luck. :)


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: '69 brake master cylinder Trap valve question
Posted by: limey222
Date: September 26, 2015 07:05PM

This may be premature but I don't think so, but it lucks like I have solved my stick front brake problem. On a whim I just removed the tiny trap valve and spring in the rear connection port of the brake master cylinder. I drove the car many times around the block, braking many times and the locking disc brake problem never re-ocurred.


88v8
Ivor Duarte
Gloucestershire UK
(719 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: '69 brake master cylinder Trap valve question
Posted by: 88v8
Date: September 27, 2015 04:54AM

Well that is just weird.
So was the previous cylinder also mis-assembled?

Anyway, if it's fixed, hooray. I'm sure your wife will be very pleased.

Ivor


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