Bleeding dual circuit (really now!)

Tor

Tor

Well-Known Member
I'm back to a familiar but hated place, and I would appreciate some help. It's where my brakes people are trying to get the brakes right in connection with a fluid change and EU inspection ("MOT"). The guy who previously said the system can't be properly bled without arresting the shuttle in the four-way cross thing by the booster, now says that said shuttle has no bearing on the bleeding or fluid passage apart from triggering the warning light when connected (it is not). He says that if this dual circuit booster feels hard and notchy he could spend hours and not get it right, and that the time/money spent far outweighs the cost of a NOS item.

I have a firm enough pedal but it keeps changing ever so slightly, indicating air somewhere in the system. Once every now and then it's like an air bubble has shifted and I have fantastic, progressive response and the car will stop on the nose - feels like how it ought to be. But then the brakes drag for quite a while, ie. until the air bubble moves again.

What's the deal?

(History: one tandem booster, overhauled with a seals kit. Not sleeved, no can do in these parts).
 
If this is anything like old Volvos I believe you have to centralise the shuttle valve before bleeding the brakes ,An old screwdriver with the sides ground off the tip used to be the tool to use
 
I've never worked on an old Volvo, but if you're saying that centering the shuttle valve on a dual-circuit P6 is crucial to getting both circuits free of air, then that's what I'm after! :?
 
I think so because if the shuttle moved to one end of it's travel, doesn't it cut off fluid flow to one circuit?
 
This is indeed the question. I will eventually find out, presumably, when I collect the car... :?
 
Hi Tor. I am curious how your story ended since i am about to fit my resleeved slave cylinder to my 3500s. Did you lock that sleeve or what? Regards Barten
 
Hi Barten,

They did indeed poke something into the junction to keep the shuttle from sliding out, then they replaced the fluid. No change in how my brakes work, however, and I've decided to send the booster cylinder to Mark Gray for stainless sleeving this winter. Seems to be as good a solution as buying a NOS booster. Might do the master cylinder while I'm at it.

I would love to hear how your brakes work when you're done?

Tor
 
Hi Tor,
I opened another issue yesterday about bleeding a duel system because your problem seemed to be different.
However, maybe you can help me out as well.
I'm having trouble with getting the air out of my braking lines. I suspect the master cylinder to suck environmental air when releasing the pedal.
Any suggestions? Thanks

Eus (new member; see my introduction in the intro section)
 
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