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Maybe the person who said they are hard to bleed meant the dual circuit 105s?

Btw note that the rear brake pipe is higher than the calipers, in some areas, so air has to be pushed to the calipers to get it out. Maybe that is why I was told, can't remember who by, to jack up the rear ... ?
Pete
 

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Quote: “I tried the bottom up method after Tom suggested it. We could not get any fluid in to the system and wondered if there is a check valve in the MC or booster that prevented it.”

Yes, weird. The Bonaldi does have a check valve at the very rear of the cylinder stopping fluid under pressure going back to the reservoir, but it is activated/closed when the m/cyl piston is pushed by the brake pedal; I shouldn’t think it would block anything under the relatively low pressure a syringe or even a pressure bleeder used from the calliper end would supply. I’ve not seen any reference to a check valve in the boosters.
If you can’t get fluid to return to the reservoir, air can’t either. Interesting....but I can’t offer any suggestions here....I don’t know what would be getting in the way.
The only component I haven’t seen mention of yet is the brake light switch....nothing evident there?
 

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Discussion Starter #383
Brake light switch is merely a pressure sensitive switch at the junction on the firewall....I don't think it could be the culprit.

Quote: “I tried the bottom up method after Tom suggested it. We could not get any fluid in to the system and wondered if there is a check valve in the MC or booster that prevented it.”

Yes, weird. The Bonaldi does have a check valve at the very rear of the cylinder stopping fluid under pressure going back to the reservoir, but it is activated/closed when the m/cyl piston is pushed by the brake pedal; I shouldn’t think it would block anything under the relatively low pressure a syringe or even a pressure bleeder used from the calliper end would supply. I’ve not seen any reference to a check valve in the boosters.
If you can’t get fluid to return to the reservoir, air can’t either. Interesting....but I can’t offer any suggestions here....I don’t know what would be getting in the way.
The only component I haven’t seen mention of yet is the brake light switch....nothing evident there?
-tj
 

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Man, you've done a lot of checking here, but seems like you haven't pinpointed it, if all these things have been changed and the symptoms remain the same.
Pedal is returning fully, not blocking any ports in the MC?
Bypass the booster hydraulically, just as a test, then bleed?
No kinks/blockages in any hose or pipe?
Pipes all installed corrected at junctions and booster?
All calipers installed with bleed screws up?
You trust the rebuild of the components?
Grasping at straws here but trying to think what might not have been thought.
Andrew
 

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Discussion Starter #385
Man, you've done a lot of checking here, but seems like you haven't pinpointed it, if all these things have been changed and the symptoms remain the same.
Pedal is returning fully, not blocking any ports in the MC?

Yup. There is no pre-load on the piston, and the brake pedal has play in it before it begins to engage the piston.

Bypass the booster hydraulically, just as a test, then bleed?

I've not tried that, but again, two separate brake boosters, same exact symptoms. Seems highly unlikely it's the booster.

No kinks/blockages in any hose or pipe?

None

Pipes all installed corrected at junctions and booster?

Yes. The brakes work fairly well. Someone unfamiliar with an old Alfa might just assume "it's an old car." The pedal just has too much travel, and isn't firm enough. If you press down firmly on the pedal you can get it to depress 4 inches or more (with the car not running).

All calipers installed with bleed screws up?

Roger that.

You trust the rebuild of the components?

Well....no actually. But I've also had problems with brand new components. I've had two new MCs that exhibited this behavior, a NOS one that exhibited the behavior, and a rebuilt (twice) MC that exhibited this behavior. I used to prefer rebuilt original parts, but now I've had both rebuilt original and "new manufacture" parts not deliver.


Grasping at straws here but trying to think what might not have been thought.

You and me both. Thanks for helping Andrew.

Andrew
-tj
 

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Discussion Starter #387
It is now being suggested that I've been using the wrong brake MC all this time, and that I should try this one https://centerlinealfa.com/catalog/clutch-master-cylinder-1969

My car was originally equipped with Dunlop calipers and at least a couple peoples' opinion is that the "Bonaldi" style brake MC is very hard to rid of air.

Has anyone used the MC in question and noticed any difference in performance?

-tj
 

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If it's truly a 69 it should have two circuits (four holes) coming out of it. Is your car plumbed that way?
I've used the early Dunlop style and the later ATE style on the same car, no issues. The way the pipes route in is a little different, but hydraulically they should be the same I think, both using a servo and thus having the same piston diameter.
I have bought ATE style ones from Classic Alfa and Jon Norman, both worked fine. That is, both pipes go into the MC body proper, not the one with the pressure line hanging off the back.
Andrew
 

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Discussion Starter #389
Andrew,

There are two master cylinders of this style, one has the dual circuits for the twin booster 69s, and the other has only 2 total.

My car only has one booster.

It doesn’t really make sense to me, and after having replaced almost every single component numerous times I’m loathe to spend yet another $200 on a component unless I’m reasonably sure it’s going to fix the problem.

The person who suggested this part is well known to us both and respected in the Alfa community.

If it's truly a 69 it should have two circuits (four holes) coming out of it. Is your car plumbed that way?
I've used the early Dunlop style and the later ATE style on the same car, no issues. The way the pipes route in is a little different, but hydraulically they should be the same I think, both using a servo and thus having the same piston diameter.
I have bought ATE style ones from Classic Alfa and Jon Norman, both worked fine. That is, both pipes go into the MC body proper, not the one with the pressure line hanging off the back.
Andrew
-tj
 

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Discussion Starter #391

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Discussion Starter #392
The continuing saga of the brake system that won't come good....continues.

With the suggestion that I purchase yet another (later style) brake master cylinder I decided to try one more thing. Perhaps stupidly unwilling to accept the probability that I've had 4 consecutive brake master cylinders that are defective, I removed the one I got from Classic Alfa, and reinstalled the Bonaldi I got from Alfa Parts. Both were supposed to be new parts. Before I installed the Bonaldi, I took it apart on my bench, inspected it for torn seals, broken pieces, etc. Everything looked normal. Before reassembling it, I pour brake fluid in to the bore, then reassembled, then poured more brake fluid in to the supply and delivery line ports. I tilted it, tapped it, let it sit overnight, and added more fluid to it. I used the little plastic caps to keep as much of the fluid in the master cylinder during installation.

Back installed, I bled the brakes using the two person method. Took her out for a trip. Same. Bled her again with the two person method. Took her for another test drive. Same.

Then I borrowed a modified brake fluid reservoir cap with a fitting for an air hose in it, and pressurized the system from the brake fluid reservoir with about 12psi. I cracked each bleed screw starting at the right passenger rear. Each time I got a few bubbles from each caliper, and then clear fluid without bubbles. I set her back down, and went for a test drive. Same.

Back up on jack stands once again. Once again I got a few air bubbles, and I don't know if they were merely still in the system from before, or somehow new air got in to it, but I let each bleed screw stay open until I had clear brake fluid flowing for 5 or 10 seconds. Back on the ground, back on the road for a test drive, and once again, same.

It's hard for me to believe I have a vacuum leak because there really aren't many connections in the system that would only suck air. Actually past the first connection from the brake fluid reservoir to the supply pipe to the master cylinder, there are none. Any other junction that might be drawing air would also be under pressure and would show a leak. I don't have any brake fluid leaks.

And so at this point I don't feel I have any options but to try the later style brake master cylinder which has the junction coming off the tail end.

-tj in the Cruz Mtns
 

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Man I feel your pain and frustration. 1 more thing to think about and check is if the pin that drives the piston in the master cylinder has an adjustment is it set perfectly. I had a problem with this on my spider but it is standing pedal dual circuit system. I'm thinking if it has caught air even before you start to bleed and it has no way to pass. Regards John
P.S. That's the pin that comes off the pedal arm and goes thru the firewall.
 

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Well, you’ve done so much, including having your local 105 guru stumped too.
I’ve occasionally had SOME trouble bleeding my car (single circuit, floor pedals, Bonaldi), but nothing that persistence and lots of fluid didn’t largely or completely eliminate, and those times when it was only ‘largely’, driving seemed to occasionally help, or the next go at it did.
A few posters have hinted at trying to isolate the problem, maybe that’s about the only thing left to help steer you in the right direction.
For example...
- take the booster out of the equation. A brake shop made me up a 6-8” female-female hose to connect the hard lines to/from the booster for $15 to do similar testing. Didn’t have to bend the hard lines that way, just removed the booster.
- Front versus rear, left versus right. If I recall correctly, you have Teflon/braided steel lines everywhere? Bit hard to successfully clamp these I expect, but do you still have some rubber hoses you can use for the rear axle and front calliper lines....clamp them off one at a time and see what happens? (You can put this back axle flex line in backwards, by the way, and it will leak. But I expect you would have spotted that.)
It’s a bit of messing about, but I expect by now you are used to that.

Re all those master cyls, unless you have REALLY bad luck, I’m with you, I don’t see how they can all be bad, in the same manner, trapping air somewhere, but with no evidence of leaks...those single-circuit cylinders are pretty simple.
 

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Discussion Starter #395
Yes, thank you. There is no pre-load on the master cylinder. There is enough free play between the piston and actuating rod.

Man I feel your pain and frustration. 1 more thing to think about and check is if the pin that drives the piston in the master cylinder has an adjustment is it set perfectly. I had a problem with this on my spider but it is standing pedal dual circuit system. I'm thinking if it has caught air even before you start to bleed and it has no way to pass. Regards John
P.S. That's the pin that comes off the pedal arm and goes thru the firewall.

-tj
 

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Discussion Starter #396
Thanks for your suggestions. The behavior has been identical across two separate brake boosters, including one which was rebuilt and tested and verified to be good.

I do not have stainless braided brake lines....a myth I seem incapable of dispelling! I have the original hard lines to the calipers.

Well, you’ve done so much, including having your local 105 guru stumped too.
I’ve occasionally had SOME trouble bleeding my car (single circuit, floor pedals, Bonaldi), but nothing that persistence and lots of fluid didn’t largely or completely eliminate, and those times when it was only ‘largely’, driving seemed to occasionally help, or the next go at it did.
A few posters have hinted at trying to isolate the problem, maybe that’s about the only thing left to help steer you in the right direction.
For example...
- take the booster out of the equation. A brake shop made me up a 6-8” female-female hose to connect the hard lines to/from the booster for $15 to do similar testing. Didn’t have to bend the hard lines that way, just removed the booster.
- Front versus rear, left versus right. If I recall correctly, you have Teflon/braided steel lines everywhere? Bit hard to successfully clamp these I expect, but do you still have some rubber hoses you can use for the rear axle and front calliper lines....clamp them off one at a time and see what happens? (You can put this back axle flex line in backwards, by the way, and it will leak. But I expect you would have spotted that.)
It’s a bit of messing about, but I expect by now you are used to that.

Re all those master cyls, unless you have REALLY bad luck, I’m with you, I don’t see how they can all be bad, in the same manner, trapping air somewhere, but with no evidence of leaks...those single-circuit cylinders are pretty simple.
-tj
 

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Ok, but BEFORE the hard lines to the callipers, there are flexible, rubber (and therefore clampable) lines LH front, RH front, and before rear axle, yes? That’s what I was getting at...clamping these in turn to see if anything changes....sorry if I wasn’t clear.
 

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Discussion Starter #398
No sir....there is only one flexible rubber line and it connects the main line that begins at the junction on the firewall to the junction on the axle.

-tj

Ok, but BEFORE the hard lines to the callipers, there are flexible, rubber (and therefore clampable) lines LH front, RH front, and before rear axle, yes? That’s what I was getting at...clamping these in turn to see if anything changes....sorry if I wasn’t clear.
 

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Ok, so there’s one of the three flexible lines.
For the front, you can’t have hard lines all the way to the front callipers. Things move up and down...there’s gotta be a flexible line in each wheel well.
If these are rubber, you can try the isolating thing by clamping them off. This is what I was getting at in post 394. If they are Teflon with a (usually) braided stainless sleeve, maybe not so easy to clamp, as they may crush instead.
 

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Discussion Starter #400
With a small amount of caution I announce that I believe I've found the root cause of the air that was getting in my brake lines and causing the soft pedal. I went back around the car and checked all the fittings and found that there were two on the brake line junction that is mounted to the firewall that I was able to get another half turn or so on. I know these are compression fittings and that they need to be very tight, but I'd manufactured these lines and put the flares on them with a handheld tool. I also used new copper tubing on a couple of the lines. Getting the flare right with the handheld tool is not easy, and it's possible that the flare wasn't perfectly formed. Cinching them down required a certain amount of sensitivity and I may just not have been as aggressive as I needed to. One of the fittings that wasn't completely tight was the one from the brake booster.

It's curious of course that it would allow air in but not push fluid out (there were no leaks) but when I tightened it and one other, and then went back to bleed the system with a pressure bleeder there were no more air bubbles. The test drive was markedly different and better, with the kind of firm pedal that feels right but still with the ability to modulate braking appropriately.

On to the next....

-tj in the Cruz Mtns
 
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