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'
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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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