pressure bleeding brakes - pedal position important?

[ragnarhairybreeks]

I pressure bled my brakes this last weekend, and it all went the way it has before, with minor problems not associated with the bleeding. Later, I was looking over the German language Vanagon repair manual for this process and it shows an adjustable strut between seat and pedal. I wonder what difference this makes, I can't visualize the flow in the m/c to come to any conclusion. Any thoughts?

here is the page from the manual:

alistair
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'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[Wildthings]

Once you push the pedal down a bit you are going to close off the ports in the master cylinder so there will be no movement of fluid through it. There are probably ways to use this to your advantage at times if you just closed off the port on one circuit and not the other. Not sure what you would gain by it though.

[ragnarhairybreeks]

Wildthings,

that makes sense. But I'm still wondering about the first image on above page, and caption:

"bremspedaldrucker zwischen fahrensitz und bremspedal einsetzen und vorspannen"

my translation as :

"brake pedal pressure between the driver seat and brake pedal bias and use"

alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[MarkWard]

Is it possible, each photo belongs to a separate task? That would make more sense.
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[r.e.wing_fc3s]

while were talking about bleeding minutae from the fsm, mine mentions a load sensitive proportioning valve that should be "activated" to let the fluid flow to the rear. my 86 only has the standard valve with nothing on it to move. was this only on earlier vans?

[IdahoDoug]

Proportioning valves are usually on or above the rear axle. They use the changing distance between the axle and floor pan as a proxy for vehicle rear axle load. A simple lever affixed between fine tunes a valve between the brake line and the split to each rear brake cylinder.

DougM
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[ragnarhairybreeks]

Vanagon proportioning valve is shown in bentley and has a prescribed mounting angle which leads one to believe that it works on a "rolling ball" type valve. No levers involved.

alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[presslab]

Maybe if you push the lever just a smidge you will allow any trapped air to escape. A stretch really, I don't think it would have much effect.

The Vanagon proportioning valve is wide open when the van is just sitting level. When stopping quickly and/or on an incline it will close off the port to the rear brakes. It's quite an ingenious device.
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1986 Vanagon Westfalia EJ25
1988 Subaru GL-10 EJ20G --- 2000 Honda XR650L
2010 Titus El Guapo --- 2011 On-One 456 Ti