Re: 105 brake booster

["Sasha Nackovski" <snackov@domain.elided>]

Bert,

I assume your car is using the dual Bonaldi booster setup?

I have rebuilt quite a few of these boosters, so I will offer some advice.
Firstly, buying new is the easiest way to go, and new boosters last well
provided you change your brake 'very' regularly. However, when we talk about
"new" boosters I mean brand spanking new from the factory, not the locally
reconditioned units that some parts vendors advertise as "new". Read on.

If you choose to recondition your own booster, note that if you merely put a
new seal kit into an old booster housing, the booster will fail again in
short time. It is not a question of it "may" fail, it will defiantly fail.
To combat this I have the main cylinder resleeved in stainless steel by a
local company. Resleeving these cylinders is not cheap, as they require
three distinct size sleeves to be fitted- two in the main bore and one for
the air valve. I believe stainless sleeves are superior to the original
machined alloy found in these cylinders. If you buy a reconditioned unit,
make sure they have used stainless sleeves in the bores.

Also note that when you buy a seal kit (available from most Alfa parts
vendors in Oz and the UK), you are really only getting a half-kit. That
means you get the parts to recondition the main cylinder, but not the
air-valve components, Unfortunately, it is usually the failure of the
air-valve seal that leads to failure of the booster- fluid leaks through the
air-valve seal, and get sucked into the main diaphragm chamber, where it
sits and eventually causes the main diaphragm to fail- which means the
booster no longer functions. To get around this problem I install a modified
air-valve piston that incorporates twin seals rather than the original
piston that only has a single seal. If you attempt to recondition your own
booster you must carefully disassemble the air valve in order to reuse the
air-valve diaphragm, otherwise you will have to buy an air-valve kit also-
which are not cheap or easy to find. Of course if the air-valve diaphragm is
damaged it will need to replaced anyway, but I usually find that they are
OK.

I should mention that I do not recommend you try to rebuild the Bonaldi
booster yourself if you have no experience with brake hydraulic cylinders-
it is very easy to screw them up.....Besides, once you add the cost of
resleeving the cylinder, a main cylinder kit and an air-valve kit, you have
exceeded the cost of buying a brand new booster.

Another option you have is to use Australian made PBR remote brake boosters,
which were found on lots of 60's and 70's Holdens, if originality is not a
concern. There are two types, the VH40 and VH44, and they are cheaper than
the Bonaldi's to buy and recondition. However, there are two problems with
this option- firstly you will have to change all you booster brake pipe end
fittings, as the PBR boosters use Imperial fittings rather than Metric
fittings. Secondly you will need to fabricate new brackets to mount the PBR
boosters in your engine bay. I have seen this conversion done on a few 105
cars (I have never done it myself, so I couldn't tell you the results), but
it makes sense from a purely economic view.

E-mail me if you have any other questions.

Sasha Nackovski- Melbourne, Australia.

>Date: Mon, 31 Dec 2001 08:33:41 +1000
>From: Bert Steginga <A.Steginga@domain.elided>
>Subject: 105 Brake Booster
>
>Happy New Year to all you fellow Digesters.
>One of the brake boosters on my 105 Alfa has packed it in over the weekend.
>Has anybody ever rebuilt one of these using a kit or should I buy a new
one?
>Thanks,
>Bert
>Brisbane
>Australia
>1971 GT Junior

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