Re: Bonaldi Brake Booster

[M.Battley@domain.elided]

>> Has anyone figured out these old style Bonaldi Brake boosters. The 
>> one on my 67 GT Veloce will not release.  I have to disconnect the 
>> vacumn hose from the engine to stop it from actuating even with no 
>> force on the brake pedal. I haven't found a manual that covers the 
>> booster.

Both Tony Stevens and Biba have suggested rebuilding the servo which 
I agree is very likely to be the cause. However before you do 
this, check the short 90 degree hose that connects the pipe from 
the vacuum chamber to the external airvalve. I spent a long time 
trying to solve this problem on my twin booster 2000 GT Veloce, 
including rebuilding the offending servo, only to eventually find 
(thanks to a hint from another digest member) that the only 
problem was that this hose was perished and was collapsing under 
vacuum, preventing the servo from releasing.  It's very easy to 
check: when the brakes are stuck on, feel the hose: in my case it 
was obviously collapsed. I pushed a smaller diameter hose inside 
it, problem solved. Tony: is this hose available?

The servos are not difficult to rebuild, even without instructions, 
(although Biba's instructions should be comprehensive enough to let 
you do the job) just make some sketches to show you how to reassemble 
it. I also spent some time figuring out how the thing worked just for 
my curiosity. You can buy full rebuild kits that include the 
diaphragm and the airvalve assembly: in my case these seemed fine so 
I just cleaned up the bores and replaced the three main 
hydraulic seals which are generic sizes, cost me about $5 total and a 
few evenings work.

Good luck... hope it's the hose!

Mark Battley,
Auckland, NZ

74 2000 GT Veloce

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