Bleeding super duplex system

[Overknasten]

I am still trying to figure out what has happened to my brake system.

Before I took of the calipers everything worked quite well. Why fixing it you might ask?
Well I had a squeaking noise from the front when the brakes were warm and I wanted to overhaul the parking brake as well.
All four calibers has been taken apart and refitted with new seals, and dust covers. New "internal" brake tubing (the four small ones on the front calipers) has been made. So far so good.
Calibers re-installed and bleeding of the front seems OK.
Bleeding the rear ones only causes a small stream of oil and a lot of AIR.
I haven´t touched the tubing from the mbc at all.
It has been standing in the garage for 2 months drained from brake fluid while I was working on the calipers.
The car is on jack-stands and the brake control valve to the rear is fully open, as far as I can see.
I understand what you describe about the mbc, but I simply cannot understand why I have this problem now given the fact that the only thing I have done is to take off and re-install the calibers.
If it is the mbc, is it possible to renovate or do I have to buy a new one?
I will post some photos of the system I have in the car now, maybe you can see if it is the right one.

Below is the last post in the old topic: Girling brake caliper refurbish
viewtopic.php?f=10&t=1408312

From Huib:

I agree with bmarler. I scanned the thread quickly and could not find anything about the master cylinder.

First of all you MUST have an original mbc. The Super Duplex system as on the 2nd series Fulvia requires volumes of the two chambers which are different from simple Duplex systems.
If you do have a non-original mbc, replace it or connect the the wheel brake cylinders in such a way that it becomes a Duplex system.

I am very quick to replace mbc's which are over 40 years old. Even a NOS one which has been on the shelf for over 40 years I would not trust.

Be aware that on the new mbc parts are used that are not resistant to brake fluid. Among those parts are the plastic parts inside the container for the float and also the O ring at the base of mbc. I replace those with EPDM O-rings.

If you still want to try the old one, check if the two parts of the 2nd (counting from the pedal) plunger still slide.

Check if all the lines are connected correctly. The first (counting from pedal) chamber serves the 8 small cylinders, 4 at the front, 4 at the back. The 2nd chamber serves the 4 bigger ones at the front. Make sure you connect them same way when reinstalling a mbc.

I suggest to take apart the mbc and post photo's here. Consider opening a new thread.

[bmarler]

i have a little bit more to say about this. your system was drained for several weeks. there was ample time for all the fluid to drain from the master cylinder. a better choice when going the route you took would be to plug the lines coming to the calipers so the system would stay filled with fluid.
but that is behind you now so we move forward. you absolutely must bleed the master first or you may never fully vent the system.
with that accomplished the rest will be easy.
the complication now though, is that the master has been sitting empty of fluid and is prone to damage from air/moisture in the system making corrosion. the other complication will be when you use the pedal for pressure bleeding. if you push too far sometimes you will break loose bits of crud inside the master that tend to build up from time and the fact that the stroke from the pedal is reduced as there is no air in the system. you already may have done some damage by stroking the pedal all the way to the floor.
it may be worth giving it a try to bleed the master and hope for the best, but at this point in your project i would probably pull the master and go through it so all the parts would be as new. then you can bench bleed the master to be sure it's working before mounting to the car.

[Overknasten]

Thanks again. I fully understand that letting in sit there without oil for some time was not clever (to put it mildly) In Denmark we haven a saying that sounds something like "From damage you getter wiser but never richer"
OK back to the topic. Bleeding the master cylinder?
I filled it up and unscrewed the connection pipes to check if oil was flowing and it was good. Then I started the bleeding sequenze.
Is there some other way to bleed the mbc?
Luckily i have only pushed the pedal down by hand and not by force. I will try and remove the jackstands to unload the brake pressure valve and see if this changes anything then I will disconnect the rear calibers once at a time to see if the problems is in the caliber, they are interconnected so i guess any fault will show in the other as well.
And after all this I will dismantle the mbc and go that way - as you suggest.
Any advise on where to buy the spareparts? Do the common Classic Lancia spare dealers have the stuff? Huib says that it must be EPDM.
Any idea sending it for renovation to a specialist like Casa Lancia?

[lancia7550]

Probably a silly question, but did you put the rear calipers back with bleed nipples at the top? I know about two cases where someone put the calipers back with the nipples at the bottom, as they fit either way, and would obviously be impossible to bleed.

Also worth trying to bleed at the rear limiter first on the brake line connection to the rear wheels to see if you get clear fluid out there.

[Huib]

Very good question indeed. It does happen!

[Overknasten]

Good point but The calipers are Installed correct.
Yesterday I took of the connecting rod from the rear axle to the brake limiter and realised that this valve is completely stuck. I will take it off and see if I can get it to work again.
First I will make some blanking nuts for the brake line connectors so I don’t spill all the oil on the floor again.
I guess I am very close to doing the mbc job now.
My concern is that the connectors to the mbc are not in super condition and right now I cannot see myself renewing the brake lines as well. Well one thing at a time and patience will get me there.

[Huib]

Several hundreds of fantastic Italians built the car for you in a few days. When you, the fantastic owner of the miracle called Lancia Fulvia works at it alone, it is only natural that it takes a few days longer.

[bmarler]

if i am only going to be opening the brake lines for a short time i just use small tapered wooden plugs for the lines. they seal good enough to slow the leakage to a few drops. i keep a few golf tees around with re-shaped tips for this purpose.

[Overknasten]

MBC renovated - check
Brake force limiter - new
All tubing connected according to manual
Question: I have adjusted the brake force limiter so that the activating rod just touches the end of the piston. Rear axle on stands as if it was standing on the road. Is that correct?
I haven’t started filling brake fluid on the system yet, any thing I should be careful about?
Tomorrow I will try and bleed the brakes again!!!
So I will either drive my Lancia in the weekend or put it on a trailer and head for a professional workshop.
Exciting 😁

[bmarler]

i don't have a brake limiter on mine so i don't know the exact positioning for it. but if there's a measurement in the workshop manual i would bet that it's taken with the can being level, and the weight on the axles.(wheels)