Anybody have insight into the workings of the brake booster
unit for a TR6?
My understanding is that at rest (ie no pressure to the
brake pedal) both sides of the diaphram are exposed to
the same airspace. This means no motion, since there's
no pressure differential.
When you press on the pedal, you upset this, and allow
the master cylinder side of the diaphram to be exposed
to engine vacuum, and the other side gets exposed to
atmospheric pressure. This differential pulls the
diaphram and thus provides the boost.
And so I thought that there was never a time when
there was an "open" flow of air into the vacuum hose
back to the engine. (perhaps a bit of movement as
pedal/valve moves, but not a continual flow)
Is this how it's supposed to work???
If so, why does a good steady pressure on my brake pedal
kill the idle of the engine? Idle is about 900-950 rpm,
but with brake applied, it will stumble down into the
600-700 range, and threaten to die. Removing my foot from
the pedal immediately restores smooth idle. My assumption is
that it opens an air flow into the vacuum line to the
booster.
Does this mean a bad diaphram? Or maybe something else?
If it's the diaphram, what are repair options? I've
heard in the past that the replacements weren't available,
but I'm not sure whether that's true or not.
Currently avoiding brakes to keep the engine running :-)
Joe
flake@a3115jmf.atl.hp.com
'72 TR-6 CC75128
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