Bob,
It sounds to me like the control valve is the problem. If it isn't moving
back and forth freely, it won't allow the "T" valve to do its thing and
allow the main piston to withdraw to the rest position (all the way back),
with the brakes off.
It sounds like it (control valve) works fine when you apply the brakes; but,
when you release the brakes, the pressure in the output line is not causing
the control valve to return to its rest position, which it is supposed to
do. This causes a full vacuum on both sides of the piston, which is the
rest position. When you turn off the engine, the vacuum goes away; and the
main piston is forced back by the big spring, thereby releasing the
hydraulic lock (brakes on).
The obvious questions would be:
Were all the seals put on in the proper direction? Were the seats cleaned
and smooth where the "T" handle valves sit?
Is the rubber grommet at the end of the transfer tube allowing air in?
Did you hone the three bores smooth?
Any scoring in the bores?
It doesn't sound like the main piston is hanging up (usually a big problem),
because when you turn it off the spring pushes it back just fine.
When I did my servo, I sent the "can" off to have it Teflon coated on the
inside to keep it nice and slippery. It's been fine for seven years.
I do think another look at the control valve and its associated parts will
show up something.
Atmospheric air pressure is staying on the back side of the main piston and
should not be when the brakes are released.
Good luck. Don't through away a perfectly good component.
Jerry Christopherson
9473187
-----Original Message-----
From: tigers-bounces+jcmc2006=suddenlink.net@autox.team.net
[mailto:tigers-bounces+jcmc2006=suddenlink.net@autox.team.net] On Behalf Of
Robert J. Wanty
Sent: Monday, December 03, 2007 6:30 AM
To: tigers@autox.team.net
Subject: [Tigers] 7" Girling Brake Servo
I have rebuilt my servo and when I have the engine running and put on
the brakes then let off the pedal the brakes hang up (stay on). If I
shut the engine off the brakes stay on unless I push the pedal then they
go off; any ideas or should I toss the unit and go to a dual master
cylinder which may increase my probability of not running a yellow
light?
Bob
B382001318LRXFE
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