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1991 Alfa Spider Veloce
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Discussion Starter #1
I set out to do the brake fluid flush and quickly realized that it will take way more than that.
Fast forward a bit and that’s how it all looks at the moment.

1642683


As you know from my other post, brake performance was marginal.
Little investigation showed wetness in the booster vacuum hose. That can’t be good. Tracking back, the booster chamber was totally wet inside. Loosen the master cylinder and it was dripping wet. Drained the brake fluid reservoir, removed it and than suck the remaining fluid out. I could not believe my eyes. Needless to say there is no saving it.
Replacement is a must. I see newer units future the 22mm bore versus the 20mm on the original design. I hope the flare nut size remains the same. I could not confirm that over the weekend. I would appreciate if someone will before I place an order.
 

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But Mad North-Northwest
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11,595 Posts
Yes, the flare nuts are the same size. 22mm gives a bit shorter, firmer pedal, which is a good thing IMO.

Unfortunately if the booster's been soaking in brake fluid for a while the diaphragm is likely to go very soon, if it hasn't already.
 
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1991 Alfa Spider Veloce
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84 Posts
Discussion Starter #3
Unfortunately if the booster's been soaking in brake fluid for a while the diaphragm is likely to go very soon, if it hasn't already.
It has failed already. I just didn’t know the reason until I started disassembly. I already got the replacement Now I’m just wondering where I can get the master cylinder in a hurry. (In Canada if possible.)
 

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But Mad North-Northwest
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11,595 Posts
I dunno how it is in Canada, but when I've ordered stuff from Classic Alfa in the UK on a Sunday I've generally gotten it by Wed or Thurs in the US.
 

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1991 Alfa Spider Veloce
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84 Posts
Discussion Starter #5
Yes, the flare nuts are the same size.
I attempted the install today and the bottom flare nut does not fit. Strange thing is that the Included plug goes in no problem in to both m cylinders, new and old. It feels very loose in the old one though.
I’ll have to contact Classic tomorrow. Anyone experience that before.
 

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But Mad North-Northwest
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11,595 Posts
The three flare nuts and three ports are all the same size, so if two went in and one didn't that's not normal, no.

You sure you just don't have it lined up right? Sometimes it can be hard to get the nut straight relative to the hole. You want to get the flare nuts attached before you attach the MC to the booster, this lets you move it around so you can get things lined up and not cross-threaded.

Worst case completely detach the MC and just try to hand thread that one screw in, see if you can get it lined up.
 

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1991 Alfa Spider Veloce
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84 Posts
Discussion Starter #8
Lucky I started with the measurements. That exactly where the problem was. The tip of the nut was slightly mushroomed and effectively prevented it from being threaded by hand. Some Emery cloth action and a bit of elbow grease solved that problem.
BMC bleed was next. Now that I was able to connect all the lines by hand I removed them and connected the bleeder tips with the tubing running back to the reservoir. Pumped the pedal nice and steady few times, waited few minutes and did it again. There were no more air bubbles showing up in the reservoir so I like to think that all the air is out of this part of the system.
Another system flush is still needed though as I couldn’t get crystal clean fluid from the back as of yet. Decided to take the car for an extended test drive to work the system hard and try to loosen any remaining residue. I think that now another quart will do the trick. I plan pressure flush with nice steady stream to finish it of.
 

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1991 Alfa Spider Veloce
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Discussion Starter #9
All as good as new now.
I’m very happy with the results. I’ll try to post a step by step with pictures on brake booster/BMC replacement as the time allows.
 

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1991 Alfa Spider Veloce
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Discussion Starter #11
just wondering, did you have to adjust the booster rod
No adjustment was necessary. The rod position was exactly the same on the used unit I got.
Boost is very predictable and soft at the start of travel. Yet with quick and firm pedal application all wheels will lock in the blink of an eye.
 

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But Mad North-Northwest
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Glad it worked out well for you. Yeah, I went from the 20 to a 22mm MC on my GTV and was much happier with the braking feel. There's no reason to use a 20mm with boosted brakes IMO.
 

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1991 Alfa Spider Veloce
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Discussion Starter #13
Vin went through some hassle on his S4 with a new booster (with an adjustable pushrod) and his brakes started dragging:
No dragging at all. There is a quick way to find out if your booster or master miss adjustment is the problem.
Disconnect the vacuum line. Will all the wheels spin free now?
Yes - adjust the boost value at rest by shortening the rod.
No - loosen the mounting nuts for the BMC to extend the rod (free) travel. 1 to 5mm max. Measure the gap and shorten the rod accordingly.
 
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