Jacob ben-David Zimmerman shcrieb;
Most elegantly,and with more detail I must confess, but as I said
previously, if the idle dips when when the brake pedal is depressed,
then there is a loss of vacuum at the brake booster.
I do not profess to a complete understanding of the brake servo unit,
however, I'm willing to learn. If anyone can shed more light on this
most mysterious of mechanisms, I would be most appreciative.
Yours humbly and most Triumphantly,
Jeff Johnson
'76 TR6
Jacob ben-David Zimmerman wrote:
>
> I was trying to catch up and came across a query re: a brake booster on a
> TR6 and a dipping idle.
>
> Joe, I'm having exactly this problem. After careful study of the booster
> diagram and the unit itself, I've decided that what's actually going on is
>that
> the O-ring at the very front of the booster - the side close to the driver -
> is bad. Thus, when the pedal is not depressed, the piston is blocking access
> to the outside air; when the brakes are applied, the piston travels back, and
> suddenly this seal is the only thing between the vacuum system and the outside
> air pressure...and if it's leaking, then you get a loss of vacuum, which will
> affect your distributor (see Tomislav Marincic's excellent tutorial on timing
> on the TR6 web at:
>http://www.mit.edu/people/zimerman/Documents/tr6/advretard.html ...blatant
>plug, sorry) and cause a drop and roughening of the engine idle.
>
> I haven't fixed this, because I've been told that I have a 'non-rebuildable'
> booster unit, so I need to replace it to the tune of $300. I'm
>constitutionally
> opposed to spending $300 for an O-ring. Others have suggested taking these
> 'non-rebuildable' boosters to a shop that works on truck fleet air brakes, as
> if anyone can make them work safely, they can...I haven't tried this yet, but
> when the car goes away for the cold season I'll probably yank the booster and
> give it a shot.
>
> CAVEAT: I'm not near the car or my diagrams. My description above may be a
> tad garbled. However, careful inspection of the booster diagram in the TRF
> catalog allows the logical isolation of the seal which is the buffer between
> the vacuum and normal air systems *only* with the pedal down.
>
> Good luck.
>
> J.B. Zimmerman
> The Triumph TR6 Web http://www.mit.edu/people/zimerman/tr6.html
> '70 TR6 #CC58880L 'Amanda'
>
> --------------------------------------------------------------------
> Jacob ben-David Zimmerman can be found at: zimerman@mit.edu
> http://uss-repulse.starfleet.com/home.html MIT/DACS
> Faster, faster, faster, until the Thrill of Speed Overcomes the
> Fear of Death. -Trent The Uncatchable/SEO
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