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Discussion Starter #1
Hi everybody!
I have a problem refilling my new brake system of my 1975 alfetta gt:

I have completely rebuild the system, changing alle the rubber pipe lines, rebuilding all the 4 brake calipers using the rebuilding kits, changed all the 4 discs and pads using brembo ones, and finally changing the brake master cylinder using a new Lockheed LM43012.
The problem is that it's two days that I'am trying to fill the system with DOT4 brake fluid without any kind of success... It's quite frustrating.
Here the procedure I followed:

Yesterday, first try:
- I have filled the brake reservoir of clean fluid, and starting from the rear right caliper I have started bleeding the system using one vacuum pump attached to the caliper nipple. The fluid seemed to arrive to the calipers, but always with lot of air inside.. I passed also the the left rear caliper and always the same. The exiting fluid, no matter for how many time I pumped to create the vacuum, was always entrained lots of air.

Then I close the rear system I try to bleed also the front calipers, but there no matter what vacuum level I reached, no fluid exited from the calipers,as if the brake master cylinder didn't connect the fluid pipe lines to the reservoir.

Second Try: using a big syringe plenty of dot4 fluid and without air bubbles I tried to fill the from system from the bottom, It seemed to work,with the fluid that starts filling into the reservoir tank, but When I closed the system and tried to pull on the brake pedal to test the system, no pressure was applied to the brakes pads which stays open.

So third try today: I unmounted the brake master cilynder and fixed it to a vice; then I connect to all the 3 exit a rubber pipe. I put the other side of the pipes inside the master cylinder reservoir and I have started pumping in order to correctly bleed the brake master cylinder. I continued until only clean liquid not entrained by air started exiting the brake master cylinder. Then using always the same big syringe plenty of dot4 liquid I have filled all the 3 pipe(this time disconnected to the brake master cylinder replaced for the moment by a bottle with some liquid) line on the car, and closed the nipples when no more air exited from the upper part of the pipes(normally using that procedure I shouldn't have any air in the system). Then I refitted the brake master cylinder to the car(and the strange thing there is that when I have disconnected the rubber pipes used for bleeding the master cylinder the fluid didn't exit like a fountain from the three exits as I expected since my brake reservoir was plenty of liquid..The fluids exit only for a second and then stopped as there was a sort of valve inside the brake master cylinder which isolated the exits from the reservoir(and in fact I have also try to use vacuum to bleed the brake master cylinder instead of pumping, but using vacuum also on only the brake master cylinder no fluids exited, the only way to bleed it was pumping).
Finally I have reconnected all the 3 pipes (already filled of fluid ) to the brake master cylinder closing the system on the car. I expected to have at the moment a system almost filled,without air or with a really small amount of it.
But when I tried to pump on the brake pedal, again no effect: the calipers stay open, the brake pedal goes to the end position without opposing a significative force, and the system doesn't work. If i try to use now the classic two man method to bleed the system when I open the nipple to fluid came out...
What is wrong with my system? Why I have no connection between the reservoir and the calipers and so I cannot use a vacuum bleeding procedure?
Why the master cylinder seems to work when mounted on the vice and disconnected to the rest of the system, and when on the car it seems that it does't nothing?

Please help me!!

Thank you very much!
 

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Discussion Starter #2
Hey Guys!

After a while I decidet to took my alfetta to the workshop.. The problem was in the new master cylinder I monted.. It was broken!! Replaced to an other new one now the car brakes!

Now I have, a part from the brake servo unit, a completly new brake system(discs, hoses, pads, master cylinder, rebuilded calipers).. BUT.. also after 50km of test driving the brake pedal is still spongy and the car doesn't brake as expected... the bleeding has been done by the specialist in the workshop.. what could it be? What have I to check? :001_unsure: :001_unsure:
Thank you very much for your help!
 

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The rear bleeder nipples are not at the top of the calipers. You must jack the rear of the car as high as you can to get them close to the top. You will get more air out of them.

The brakes will also improve after driving a bit and a re-bleed.
 

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Once you have solved your spongy pedal issue (Clayton's suggestion sounds right to me) you might then want to look at different pad compounds if you are still not happy with your pedal feel.
Pete
 

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Discussion Starter #5 (Edited)
Thank you very much for yours suggestions! I'll try! For the Pad I have bougth Brembo's ones they should be quite good.. In the meanwhile I have also built a pressure bleeder..I'll try to use (with the rear of the car jack up) it, in order to bleed as better as possible!
 
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