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early double brake MC: why this valve under the banjo bolt reducing braking at the rear?

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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
As probably known from another thread on the brake system and the early USA double brake cylinder, I am in the process of renewing it myself. Taking it out without following the factory guidelines for taking both MC's together with the whole pedalbox assembly was not easy and required removal of the banjo coupling and hollow bolt at the rear before it could be removed with the piston pushed inwards to the max. During this process a tiny valve and spring fell out this orifice. When I found an old unit back, fortunately its valve and spring were still in place so it was clear how to put the other one back in. See picture showing the new unit with its spring and valve lying outside the MC but in the proper direction. This way its tiny hole reduces the flow of hydraulic fluid when braking at the rear, while this valve opens when no longer braking, so fluid goes back in much more quickly. Why is this so, one would expect faster braking and slower deactivating of the rear brakes. Does anybody on MGE know the background? Going through the manuals and a lot of parts lists made me find only one picture with such a valve shown, but not with a spiralled spring

Tomorrow I will mount the new unit in place and start bleeding, hopefully with my Ezibleed working on lower pressure level, sometimes the large reservoir cap leaks

PS My regular parts supplier did not know this either, although he mentioned better brake bleeding with it.

PS2: strange, my user name and last post indication are not present in the column to the right, although my signature was added by me



Edited 3 time(s). Last edit at 2019-03-14 09:33 AM by Donthuis.

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Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, NC, USA   USA
As always..





Gary

Hammer: Originally employed as a weapon of war, the hammer nowadays is used as a kind of divining rod to locate expensive car parts not far from the object we are trying to hit.

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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
I thought I remembered this JT video well, because I looked at it multiple times before my own, successful refurbishing action on this double brake MC over 25 years ago. Somehow this part at the beginning about those valves did not make a lasting impression on me, so I forgot it. Thanks Gary, for reminding me thumbs up

Contrary to what JT said: since these valves have a small opening, residual hydraulic pressure goes down to near zero over time anyhow eye rolling smiley


In reply to # 3908546 by Gary E As always..


I RE

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ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, AB, Canada   CAN
1971 MG MGB
Kelvin made a post quite some time ago that explained the valves. However, I can't find the printout of his post and so far "search" hasn't been my friend. I think Skye cleaned up the data base because old messages don't seem to be here any more.

I am attaching a diagram that shows the direction of the valve.

I'm also attaching a scan of Kelvin's message, post 1662272. Be sure to read to the end because the initial post got things backward. Grr - apparently the PDF is too big so I'll post the first page in this message and the second in the next.



Terry Ingoldsby
terry.ingoldsby@DCExperts.com


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ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, AB, Canada   CAN
1971 MG MGB
And here is page two of Kelvin's post



Terry Ingoldsby
terry.ingoldsby@DCExperts.com


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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Yes this is the direction I found it in, not in reverse (although at first I thought this should be the correct way)
So Terry, Kelvin was not the first to make such a mistake in thinking....grinning smiley

PS I added his picture, now turned 90 degrees which I was looking for MG

In reply to # 3908600 by ingoldsb And here is page two of Kelvin's post



Edited 1 time(s). Last edit at 2019-03-15 03:36 AM by Donthuis.


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sandglowB Avatar
sandglowB Gold Member Al Blosser
Uniontown, OH, USA   USA
1977 MG MGB
good info



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NAMGBR since #1-263
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