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brake bleeding problems

Posted: 28 Dec 2022, 21:07
by ZsZ
Hi all!
I have problems bleeding my brakes.
Brand new ATE rear cylinders, few years old master and then renewed front calipers.
The problem:
I bleed the brakes with the help of my girlfriend, everything is OK, no bubbles, firm pedal, then I start the engine and push the pedal hard an it is soft. It even kinda feels like when the master was bad, the pedal sinks slowly if I push it really hard.
No signs of leak anywhere.
Is it possible that the few years old Cifam master cylinder gone bad and bleeds through?
Still air in the system somewhere - in the bias valve for example? I have bled a quarter to half a litre from the two cylinders combined.
Tomorrow I will buy more fluid and try to bleed it again.
Any other thought?
Thanks! 
 

Re: brake bleeding problems

Posted: 28 Dec 2022, 23:24
by mioba
Sounds odd. Press pedal a few times when all closed. Then bleed firrherest to nearest. i always gravity bleed.
Do your clutch circuit too

Re: brake bleeding problems

Posted: 29 Dec 2022, 07:28
by ZsZ
Definitively strange.
I hope that not the master again as the big brands like TRW, Brembo or ATE are really expensive while the cheaper CIFAM and METELLI could be the same bad quality.
We will see.

Re: brake bleeding problems

Posted: 29 Dec 2022, 08:14
by ZsZ
Read some samba and 80-90 brake bleeding posts, and it seems like the shoe adjusting method is super critical.
So first I will re-adjust the shoes then bleed again.
If no progress then time for MC rebuild (I hope it is not rusted inside in these few years)

Re: brake bleeding problems

Posted: 29 Dec 2022, 09:32
by weimarbus
I had trouble with mine after new slave cylinders and shoes, some slave cylinders even ATE (Chinese) do not have an internal spring and retract away from the shoes when you take your foot off the brake pedal this means that when you next press the pedal the first pedal press becomes lost motion to take up the play. I was told by supplier that they have had no issues and they sell hundreds, fitted more new cylinders ATE (Italian with internal springs) from Br..w..ks no more issues :ok

Re: brake bleeding problems

Posted: 29 Dec 2022, 16:41
by ZsZ
These were made in italy - at least the label on the box said that :) They seem to have the spring inside.

Re-adjusted the shoes with the handbrake cable loosened, re-bled all around, now the spongyness is replaced by springyness. Just like it was before - which is a shame as I also replaced the lower retainers and the adjusters in hope to have a more stiff pedal feel.
And the pedal still seems to sink a bit when fully pressed down hard with running engine.

Now it is usable - MOTs were done like this -, so I let it alone and will fall into the master cylinder - pedal pin - brake booster - brake hoses rabbit hole later.

Autofren, ERT, and Frenkit repair kits are available here, The Frenkit has better rubber as I remember, so I will order one just in case...

Re: brake bleeding problems

Posted: 01 Jan 2023, 16:23
by SurfT25
Last year I had same problem after sorting the rear arms and braking system out.
Learned (via my Bently)that i had put the adjuster screws back incorrectly.
One has an L stamped on it so assumed it was for Left side, turned out that Right side has L the lefthand thread and Left side has the righthand thread.
Just check you haven't done as I did.

Re: brake bleeding problems

Posted: 04 Jan 2023, 16:13
by ZsZ
THX!
I did assembled the springs and the adjusters in the correct way, just made the adjustment wrong. I did not check with the drum pulled yet but the self adjusting seems to work. The springyness of the system is caused by something else. 
Probably the hoses, rear drum plate, or the pedal assembly with the booster.