Passed Test
Posted 26 April 2021 - 01:07 PM
Hello,
i have 74 Mini with GMC159 master cylinder and PDWA valve. All 4 drumm brakes. On the rear frame I have inertia valve 13H7757.
The master cylinder GMC159 is no longer available on market.
Is it possible to replace with another master cylinder? I bought GMC227. The PDWA valve i will replace by brake limited valve FAM7821. It is a right combination? It will work properly?
Thank you
Martin
Moved Into The Garage
Posted 26 April 2021 - 06:57 PM
I don't see why you can't use that Master Cylinder, however, be aware that the Front and Rear Port connections on to this Master need to be swapped around, ie, the Rears come off the bottom Port.
The item you've referred to as a PDWA Valve is in fact a Pressure Differential Switch. In use, this senses if there's a difference in Hydraulic Pressure between the front and Rear Circuits. If they are about the same, happy days, if there's a significant difference here, then it will activate a Switch (and bring on a Light) to show there's been a Brake Fail in one of the Hydraulic Circuits. You can likely leave this in place. When bleeding the Brakes, if doing one wheel at a time, this will activate, once they do, they need to be Reset, which is done by removing the Switch, standing hard on the Brakes, then refitting the Switch, though sometimes, they need help.
I would strong recommend against fitting one of those FAM7821 Valves. This is just a Pressure Shut Off Valve to prevent the Rear Brakes from locking. As you already have the Inertia Valve, run with that. These are the best Valves they offered on any Mini.
One Carb Or Two?
Posted 26 April 2021 - 08:31 PM
This is a similar scenario with MG Midget braking systems which activates a fault using a brake failure warning system.
I only know because of working on the brake systems and this is familiar with the 1500 MG MIdget. I have the pleasure of owning one !!
They are tricky buggers to set on a Midget, I suspect the same as Moke says
Go along with Mokes suggestion as I have done with this system, it does work !!. It is not the same system you are using, but very very similar, in the respects of some crank ideas Leyland / BL come up with - all the same company - issuing parts they had little money for - always moaning about and never making money , I wonder why ??
They are not PDWA valves, but near as near as near as dammit - s hhhh one t systems
Edited by richmondclassicsnorthwales, 26 April 2021 - 08:51 PM.
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