Joe,
Normally, if your idle is drawn down by the action of pushing on the
brake pedal, it means you have a vacuum leak. Check your hose going into
the booster- it may be have dry-rotted and your booster is not receiving
any vacuum.
Jeff Johnson
'76 TR6
Joe Flake wrote:
>
> 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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