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Discussion Starter #1
Has anyone rebuilt a Bonaldi / Benditalia / Bendix brake booster (they are the same I believe). I know the simple solution is to buy a reconditioned unit, but I am in fact only cleaning the booster as it has been on the shelf for a good while without covers on the vacuum and hydraulic ports.
The vacuum chamber / air valve sections are no problem, it is the hydraulic cylinder I am wondering about, I see with a rebuild kit there are various seals and a circlip that you get, but on this cylinder there is no circlip to remove to gain access...any ideas?

Not knowing what the seal system looks like inside the cylinder, I am reluctant to try to rinse of flush out any dirt that may be in there.

thanks
 

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Hi, there is nothing too much to worry about inside the booster. The bronze bush you show in the photo should be a very light press fit (assembled by hand and retained by the diaphram assembly) so they come out with little effort. Try holding a suitably soft block of wood on the ali face and giving it a good knock down onto a solid surface. Behind the bush is a wire clip retaining the rest of the assembly. It is lightly spring loaded so ease it out and be careful and do it somewhere clean. Easy as you go and take photos as it comes apart and you will be fine. Good luck
 

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Discussion Starter #3
Thanks very much, you were spot on! The bushing took a little bit of coaxing but did come out relatively easily. Glad I did so, because with the amount of gunk and corrosion I found inside the cylinder, the booster surely would not have worked properly once installed.

So I think I understand how this thing actually works now, someone please correct me if I am wrong.

Under normal operation (no braking), the vacuum is applied to the front side of the booster "can" via the banjo fitting/air passage, and also to the back side of the can via the air valve (pentagon attached to the hydraulic cylinder) . With both sides of the can at equal vacuum, there is no assist to the brake. Once the brake pedal is pressed, the hydraulic pressure increases, and moves a small piston that actuates the air valve . This new position of the air valve no longer allows vacuum to pass from the banjo fitting to the back side of the can, and simultaneously allows ambient air pressure to the back side of the can (via the small "filter" on the air valve). Under this condition, the two sides of the big can are no longer at equal vacuum, causing the diaphragm to move inward and push a small rod/piston into the hydraulic cylinder, causing more hydraulic pressure, and effectively giving assist to the braking.

The arrow in the attached picture points to (as I've assumed) the small piston that actuates the air valve. Is there any way to clean/service this part? On the brake booster currently in my gtv, I am pretty sure that this is the part that is sticking (in the "up" position) resulting in vacuum assist sometimes even when the brake pedal is not pressed. Since the inside of this hydraulic cylinder was quite dirty, I want to ensure the same thing doesn't occur.

andrew

ps it looks like there is still a check valve in the cylinder, does this come out somehow also?
 

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Just a thought

I have read somewhere else on the BB about a possible cause of the sticky booster. The external vacuum pipe that goes from the pentagonal valve to the diaphram housing has a little rubber bend as it goes around the corner. This can collapse with age and I think cause sticking brakes.

Otherwise the little piston you show just needs to be clean and make sure the ali housing bore is nice and clean with no corrosion.
 

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Discussion Starter #5
thanks

Thanks, I think that I will reassemble it now, and give it a go on the car. Very good point about the hose, because if that leaks, then the booster is giving assist (even if you don't want it...). I have headers on my car, and given the proximity of this hose to the hotter than stock exhaust (meant literally in this case!), I am sure the hose is not in great shape after 37 years of service (on the car now is a Lockheed booster still with original crimping, no V-band or other evidence of a rebuild).
thanks for your help.
 

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be very careful when you clean that bore. Being that the housing is aluminum, if you over hone it or polish it to much, you can over bore it and then it won't seal.
 

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Discussion Starter #7
The bore was in pretty good shape, so I only used a paper towel to clean it out.

I guess the only hesitation that I still have is not knowing if that little piston that actuates the air valve is siezed or not. It looks like I would have to used pressure (hydraulic or air) to get it out, since there is nothing to grip on to to pull it out (or even budge it for that matter). Shall see on the car if I have power assist or not...:eek:
 

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I know this is kind of an old thread but I thought I would post what I learned this weekend. I have been rebuilding the boosters on my '69 Spider and didn't see any way to remove the air valve piston. While fooling around I found that if you run the booster plunger back and forth in the right sequence the air valve piston will pop out. It's easier to describe with pictures:

Booster 1.JPG
How the heck do you get this out? And what the heck does it look like?

booster 2.JPG
So I inserted the booster plunger and ran it up and down to see that the spring was working and see which port was drawing air.

Booster 3.JPG
With the piston in the fully compressed position I covered the side port with my thumb and drew the plunger back and...

Booster 4.JPG
Out popped the piston! Actually this is re-inactment of the actual event. In truth, It shot out about 3 feet - I was lucky it didn't go down the floor drain...

Booster 5.JPG
ANd this is what it looks like. It has a small rubber seal on the end.

That's it. Hope this helps someone...
 

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I tried rebuilding mine, but they both leaked like crazy. It was the biggest waste of $200 I have ever seen. Its one of the reasons I went to the single circuit system.

Will
 

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Will:

What rebuild kit did you use and where did it leak? I actually have two sets (4 total) of these boosters - two that came off my recently working spider and two from an unknown parts car. I disassembled all of them and spider units mostly just to paint the bodies and replate the booster housings. Otherwise the spider units were in good working order. I soon found that the spares were anything but - the plungers are seezed and I can't get the bronze bushing out of the nose. There was lots of hydraulic oil and rust in the booster housings and sludge everywhere. I thought it might worthwhile to rebuild them but by the time you get done buying kits for the body and the air valve you may as well just by a new assembly.

Interestingly, I imagine that the bulk of the cost of the rebuild kits is for the rubber vacuum diaphrams. In my case, all the diaphrams look brand new - no wear or distortion whatever. If I could just find that filter element in the air valve, a couple of cup seals and a couple springs I would be in business for a few bucks max. Alais, no luck so far...
 

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Both of mine leaked from the large diaphram to begin with. Then they leaked from the small one. After that they leaked from elsewhere. I pulled them completly apart replaced all the gaaskets and seals, and they still leaked. I guess sitting for 30 years finished them off. At first it was only the rear one that leaked, I thought I fixed it, then the front one leaked, thought I got that one dialed in only to have the rear start leaking from another place. I was stuck between a rock and a hard place and chose to ditch the second one all togther. I have to say the car stops just fine.

Will
 

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Filter Alternative

I made my filter elements by pulling a standard industrial pneumatic silencer to bits to get the silencer element out which is essentially a filter (a Festo unit worth about $8). Then I machined the outside diameter to fit which took a couple of minutes on the lathe. I had a new nose seal made by Sealjet here in NZ. Nearly six months down the track, although not many miles have gone by the boosters seem to be working a treat.
 

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Discussion Starter #13
I actually purchased a filter kit from a Mini shop (I noticed that the servo on my Mini was very similiar) and in fact it works just fine on a Lockheed booster. The filter assy for the Bendix looks identical also (but I have not verified this).
Here is the link
http://www.minispares.com/Product.aspx?pid=36143
I replaced the whole filter assy (including the new plastic cover), but I don't see any reason why you couldn't reuse the original metal cover, which looks better on an Alfa.....
At the end of the day, the filter assy was not my problem, so I didn't really solve anything, but nevertheless, at least there seems to be a source for these parts.
The comment about it being cheaper and less hassle to just replace the whole booster is probably quite true, given that the complete boosters are readily available. But if you are sure that you filter assy is the culprit, then replacing the filter assy is certainly much less expensive that the entire booster.
 

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I just took out both boosters from my '69 spider and came across this post so I thought I'd get the collective wisdom of the forum on my situation.
The symptom was that I was losing brake fluid and getting white smoke out the tailpipe.
When I disassembled the boosters, both had lots of fluid in the the chambers. The diaphragms look fine and the small air valve diaphrams look ok too. The rubber seals in the cylinders don't look too bad either. Still pliable.
What would be the failing part causing fluid to enter the chambers? The cylinder walls and the larger rubber seal? Is that it?
The power assist seemed to be working ok before the incident with the white smoke. Should I just rebuild the cylinder and expect that it will be fixed? I see that IAP has a rebuild kit for $88. Is there a better source? Who sells complete boosters?

Colin,
Apex, NC
 

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My guess would be that the rubber seal that works against the diaphragm plunger, is worn. The would let fluid enter the vacuum chamber. Being the body of the units are made of aluminum, dirty fluid is most likely the culprit for early failure IMO.
I have seen the rubber "elbow" decompose to where it is just a remnant of its former self, and any good vacuum hose will suffice as long as it is long enough to not kink in the middle.
These units are as we can see are simple in design and easy to repair. Rarely does the big rubber diaphragm fail. IMO, it is the body that wears until the clearances are out of tolerance.
Can these units be resleeved? (question for a machinist)
 

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broken plastic thingy

I just noticed that the cone shaped plastic piece that goes on the end of the long spring and has some oil flow passages in it is cracked in one of my boosters. Do any of the rebuild kits have this piece? Anyone have a used one to sell me?

Colin Verrilli
Apex, NC
 

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I'm new to the list and own a 1971 RHD 1750GTV with twin Bonaldi/Bendix boosters. I am wondering if anyone has any exploded diagrams of these and if so, are they willing to post them? The reason I'm asking is that mine need repairing and before I pull them apart, I'd like to know what I'm getting in to.
Regards,
Chris
Australia
 

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Chris, I got these from Jim last year for my GTV restoration. Now so far I've dissassembled my boosters and picked-up 2 repair kits...but haven't started the rebuild yet so I can't offer much more than this at this stage.
 

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Rossano,
Thank you - these will help a lot. My car is undergoing a slow rebuild and I'm up to the brakes. When I dismantle the boosters I'll take the hydraulics to be professionally cleaned and possibly resleeved if necessary. I've already had the calipers and master cylinder overhauled and the brakes work quite well with no vacuum assistance though when a vacuum is applied the brakes are partially on the whole time. I'm assuming the fault is in the air bleed part of one or other booster, that is, the valve is stuck open to the atmosphere all of the time. I'll see how I go with it.
I've always called my old car my Summer Car - summer time she go and summer time she not go ..... at present it's at bit of a mixture.
Thanks again and all the best for 2008.
Chris
 
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