[Mgs] Brake failure warning switch

Bob Howard mgbob at juno.com
Wed Dec 26 06:37:24 MST 2007


Rick,
   When changing fluid on my MGB, I have just flushed clear fluid through
the warning switch w/o removing it from the car or disassembling.  It
appears to me that, unless there were a large clot of rubber stuck in the
thing, it would work because of the pressures involved. 
    The piston inside should be centered normally. If there is a
difference in pressure in the front / rear circuits, the high pressure in
one pushes piston to the low-pressure side, and (with luck) activates the
warning light circuit.  
  It seems to me, then, that you could flush it in place satisfactorily,
and, by building pressure in one side then the other, determine that the
shuttle is moving. Eventually you must get the piston back to center
anyway, and the movement of the piston would dislodge any dirt in the
unit.  Last time I looked, Moss had the repair part kit and the switch in
catalogue.
Bob

    
On Tue, 25 Dec 2007 09:03:40 -0800 (PST) Rick Lindsay
<rolindsay at yahoo.com> writes:
> Good morning folks and Merry Christmas!
> 
> Question for the folks who know brakes:  Should the
> brake failure warning switch be disassembled to clean
> it?  Is that even possible?  Or should I just clean
> and flush it with brake fluid on the workbench until
> the internal piston moves freely?  Advice?
> 
> My car has a new master cylinder (done by PO) and I
> have replaced all the flex lines, rebuilt the front
> calipers and replaced the rear slave cylinders.  I now
> need to flush out the hard pipes before reconnecting. 
> My guess is that I should do that in the same order as
> bleeding the brakes - longest pipe run first working
> toward the left front (LHD).
> 
> The old fluid in my car is still clear so I don't have
> much threat of decomposed rubber in the system. 
> Still, it will all be flushed clean and recharged
> properly.
> 
> rick / '70 Split-bumper Tourer


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