Alfa Pages

[Brit01]

As a few of you may knowalready been having an issue with revs dropping when braking, especially noticeable when I brake hard to a standstill at lights for example.

drops to 600 or so then rises again to 850.

Got some brake fluid to top up until I get it into the workshop. Below the MIN level just a tad.

I did the brake test. Started the engine with brake depressed.
The pedal slowly got softer and sunk a little.
Booster appears ok but could have a small leak/tear.

I guess I can check the one way valve by removing the end that attaches to the booster.
Start the engine and see if there is a vacuum present.
Or just buy a new one. Think they are pretty cheap

this guy changed his check valve and fixed the rev drop issue. worth a try


http://honda-tech.com/showthread.php?t=2969816
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S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Bobkelso]

Hi Brit, interesting post,
I think I have similar issue with my 33..
..on the list of to do things..
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Alfa 33

[Brit01]

[Bobkelso]

Hi Brit, I have no idea, in my case the effect is
moderate and I have been used to it..
Actually I swapped the 33 as second car
and I'm post-posing many small repairs to it
for when I'll have a period with more time

I'm hoping is just the check valve as the paper
in your link suggests..I'm not sure because
vacuum reserve is small in the 33,
the booster is a small 7 inch one...but it make sense
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Alfa 33

[Brit01]

[Bobkelso]

I also thought about already, is quite a complicated work.
Original alfa 33 brake booster is a single diaphragm (7 inch diameter) booster with 203 mm external drum diameter, you can:

a) fit a single 8 inch diaphragm booster,
if you want to have similar aspect to the original and full compatibility
with the original pump (20,6 mm diameter with 3 out lines)
you can use the gold galvanic plated single booster from alfa 75
(227 mm external diameter of the drum) that is from same brand than the one of 33,
it was fitted also on other cars and old light trucks like fiat Ducato,
but there is no the space to straight fit it, 75 drum is 12mm bigger in radius than the original of Alfa 33, and:
- one side of the original booster drum there is the air ventilation unit, in between you have 6-9 mm free space in series 3 models,
- the other side you have the clutch oil pump, only 3 mm of free space available (6 mm if you think about to grind the pump on the side),
- below the drum there are few mm (about 3-6mm, or some more mm if you put a 10-15 mm spacer between the black frame and the booster);
So, to create the space for a 8 inch booster you have to heavy modify the black frame where
the booster, the clutch pump, and the pedals are attached, moving the booster position:
- 6-10 mm up
- 5 mm more side away from the air ventilation unit,
- have to move 10/15mm side away also the clutch pump
(also welding new small parts at the black frame may be needed),
After this you have to modify the brake pedal connection to the booster (the position of the fulcrum) to make it work
at the correct leverage and angle as original one, and a minor modification also for the clutch pedal (fulcrum moved on the side),
or to make it a little easier you can move up 6-10 mm all the 3 pedals and their common axe,
probably many many time needed to do all this when done first time;
this will give you stronger brakes and an aspect very similar to original;

b) any other 8 inch booster more modern and easy to find,
they have the drum with external diameter some mm less respect the older one like the gold one from alfa 75,
so they are a little easier to fit, but you have to verify compatibility with original brake pump
or use the brake pump that comes with that booster;

c) you can fit a double (tandem) 7 inch diaphragm booster
( 7 inch + 7 inch, about same working area and strength of a single 9 inch diaphragm booster),
the black one from Smart model 2007 is ok as it is 200 mm external diameter, it fits in the 33 in the same lateral space of the original one (203mm),
but as double booster type is longer than single type you have to fit a brake pump shorter than the one of 33 for longitudinal space limitation,
for example the brake pump from Smart 2007 himself is very compact
(with 2 out lines and 23mm inner diameter, against 20,5mm of alfa 33 pump, but 23mm should be ok with the double booster help)
or for example one from old fiat-seat-opel models (20,5 mm with 4 out pipe) if it fits the booster;
(for this there are online some catalogs of brake pumps, like from Metelli site)
You will have to adapt an oil reserve tank (and if you don't find a reserve tank compatible you can use soft pipes
to connect tank and pump like in the Smart donor car, where the 2 connections on the pump to the the tank are positioned horizontally)
and adapt the 2/3/4 out lines from the pump to the 3 brake pipes on 33
(but this is quite easy, many photos and guides on forums about this already done on other cars);
this upgrade seams to me a solid option, it should give a modern touch at the pedal brake
(both short travel using the 23 mm pump and strong brakes with the double booster)
but it will be quite easy to detect as a modding, here in Italy it will be a problem to make it legal.

d) if you want go radical, double 8 inch diaphragm booster for example from old Volvo models
(the older are gold and rounded, the more modern ones from 740/760 series are black and sharp angled)
with a short brake pump and all the adaptations needed of option a),
probably this will give a 100% or more gain in braking force..

e) the booster upgrade in alfa 33 will be the more correct way to improve brakes for street use,
as the original 7 inch booster (and may be 6 inch in early alfa 33) is ridiculous for today standards,
but actually I think that to get a moderate gain (30-50%) is more simple mount 256mm vented disk
with 14 inch rims and uprated calipers (the ones from opel/vaxaul) at the front
and original brake pump like described in the other post on this forum,
you will have same gain in force and also, is one is interested in this, more resistance to fading,
at the quite reasonable price of 1,5 kg more on each front wheel and very few mm of more travel at the pedal..

Actually I cannot, problems with time and space where to work, but if some one reading the forum
would try the brake booster upgrade it will be very interesting, for me it is a major alfa 33 fault..

[The Wombat]

Could always replace the vacuum assisted booster with a hydraulic assisted one.

I have not researched what is for sale in UK, but it was a readily available mod in the US for boosterless muscle cars, or to ensure brake assistance on cars with a positive pressure manifold (supercharged).

I bought one for my '72 Dodge Challenger but never fitted it (car now sold). Its sat in my garage in a box and I am pondering!!

Principle is the same as a vacuum assist, except hydraulic pressure (per Citreon), and uses a take off from the power steering line.
_________________
Drivers:
- Green Fiat 20VT Coupe
- Champagne 155 V6
- Winter Freelander
- Mrs Wombats Freelander

Projects:
- Various 33s
- Some 155s

Hibernating for 2015
- 75 3.0 Cloverleaf
- 155 Q4 Winny
- Red 33 16v

[Brit01]

Actually was just looking at the vacuum pumps today.
Check valve changed.

Very bulky and noisy i believe and you still need the drum.

funny behaviour today I noticed.
While idling if I pump the brake the revs drop with each depress until stalling.
Blip on the throttle and back to normal.

Drum damaged? ?
_________________
S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Actually was just looking at the vacuum pumps today.
Check valve changed.

Very bulky and noisy i believe and you still need the drum.

funny behaviour today I noticed.
While idling if I pump the brake the revs drop with each depress until stalling.
Blip on the throttle and back to normal.

Drum damaged? ?
_________________
S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Bobkelso]

Hi Wombat..Hi Brit..I never thought about hydraulic booster because
I don't know if I will be able to make it work right,
seams really more complicated, and here are quite expensive and exotic,
I read about some upgrade using that type only on "luxury" vintage car,
and I think it is used also on truck, surely it work if well done,
may be in USA or other country is more common and affordable,
Don't know also if it use a non negligible power from the motor
or if using steering oil pump will be the same that without it.

Though about also to put a vacuum pump on the 33 original booster,
some small pumps that were moved by a belt like the one in old diesel car with (peugeot 205, etc),
putting one more belt on the A/C grove on the crank pulley but gain will be not predictable
(original vacuum booster should work conserving maximum air depression from the motor,
I think something like -0,6 bar, with a pump may be it will arrive at -0,8 bar ? really I don't know,
I should ask to a booster repair specialist if important gain if possible or not)
If one want to go on predictable and rapid results the disk swap seams to be the more easy way

Ps.: Brit, about a possible damage at the drum or the inner valve, you can hear air entering
from the pedal area while depressing the brake pedal (leaning air-fuel mixing at one carb) ? Have you got some indications
of good or bad working from the various booster tests suggested in your link or you got unclear results ?
Or may be booster is ok but you could have carbs axis with some plays?
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Alfa 33

[Brit01]

[Brit01]

I do hear a significant wushing type noise when depressing the brake pedal.
Is this normal?
Or is it unwanted air entering?
_________________
S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)

[Brit01]

Strange as this issue has almost disappeared! !
I filled the brake fluid to the max and after about a week the phenomenon began to disappear. But I still need to change the fluid and check the system.
_________________
S2 33 1988 1.7 QV
Dellorto DRLA40 (32mm venturi)