Need expert advice. Cannot bleed front brakes. 73 bay.

[Jrh5r]

Long time lurker, few time poster. I was given a 73 T2 by my folks and am on the last roadblock I think, aside from wasting more hours on how to put in the gd front roll up windows

I need help figuring out how to bleed the front disc brakes on this bus. The back brakes I have fluid to. The front brakes I cannot get a drop out of or even a sound of air. I bought a new Brazilian made master cylinder and a new brake servo, which I think Is an airtech, if I remember correctly. The manual is really vague as far as I remember reading today... I recall it saying 68-70 to leave a 1mm gap between the pushrod and mc. Beyond those years, I think it said to fine adjust by removing the Clevis pin and turning. I have the brake arm to the stop and I have nothing. I will note that the front half of the reservoir looks filled with fluid, as it appears to move around when I pump the brake arm and have a flashlight on it. That’s the side supplying the back brakes. The other chamber looks dead empty, or maybe it’s full and there’s no air?

I bought new master cylinder seals that connect to the reservoir. They were too large to fit in even with a lot of silicone and force and a small amount of heat. I reused the old ones off the original vw mc. The seemed to be fine. I have cracked the line at the mc supplying the front discs, and have nothing there.

All lines are brand new. Everything is tight. I have triple checked. No fluid coming from anywhere. No sounds of air escaping. Literally everything is new on this bus. Calipers are from O’riely. I cannot recall if the secondary reservoir on top of the mc is connected or not. I don’t think it is. The booster is not hooked up, as it seems that it should have no role in the bleeding portion.

I am thinking that this is either a clogged mc or defective out of the box mc. It’s hard to find quality parts. I tried to save a penny and bought the Brazilian made one. I am thinking to remove the mc and bench bleed it. I spent all day on this, and is my last roadblock to cruising.

Any advice appreciated.

TLDR; no front brake fluid

[ImAddicted]

Did you bench bleed the MC before installing it?
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1979 Transporter (sold)
KC1MUR

[skills@eurocarsplus]

did you set the gap for the push rod?

when i say that, i mean the one between the booster and master. it is very possible that is wrong and adjusting the outer push rod (the one with the clevis) won't get you there.

beyond that, i'd say you have a bad master. never in my professional life have i ever bench bled a master. it's possible while fooling around you shaved a crumb off of the reservoir grommet and that's plugging the feed hole to the master
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[Jrh5r]

[Jrh5r]

[ImAddicted]

Chasing down things like this are a pain, I wish you luck. Bench bleeding isn’t necessary, typically, but I’ve been doing it on my daily as well as bus the last few times because of crappy quality aftermarket parts. While it won’t find every issue, it does help identify a dead player out of the box. Ray Greenwood has a post someplace on seals and prepping a Mc before installing, not sure if it will help you in this situation or not.
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1979 Transporter (sold)
KC1MUR

[Jrh5r]

After watching this, https://youtu.be/Xeiml3VcuNo it makes more sense that the clevis adjustment won’t get me to where I need to be. I do recall a little force being needed to seat the master to the servo. I’m betting this is the issue, like skills said. The question now is how far in do I go? It sounds like just a trial and error and attempt to get close to 1mm. Sounds like the rod from the pedal lever to the mc can bring me home if I can get it close and get that preload off the master. I’ll update tomorrow just for follow ups sake.

[kreemoweet]

[skills@eurocarsplus]

[timvw7476]

it's a real grind. bench bleeding. I went with a 1 quart milk container cut open & enough brake fluid to immerse my new MC in it. Yeah, it seemed to work, but I also took out my caliper bleed screws, made sure they were clean at their tips & wrapped teflon tape around their threads. THEN I could get some fluid movement. The new grommets were useless for me too, had to rely on the oldies. Good Luck with it.

[Jrh5r]

[skills@eurocarsplus]

not sure i understand....

you want to adjust it with no pressure on the pedal or rod, as in the brake pedal isn't being activated.

adjust it from the master cylinder side inside the booster itself

when you say "adjust with the brake pushrod to the stop" i think you mean with the pedal up and the arm against the rubber buffer on the floor. that is the way you want to do it.

basically do NOT depress the brake pedal while doing this adjustment
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[Abscate]

It’s probably a 1mm pitch thread on the pushrod( you can measure it easily )

You can unscrew until it touches, the retract it 1 turn to get the clearance, Clarence.
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[kreemoweet]

The pushrod in the booster (or the one in the pedal linkage) being misadjusted is not going to affect the ability of the m/c to push fluid thru the lines to the caliper. It's either a bad m/c, empty reservoir (see OP's first post), or blocked fluid passage somewhere.
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[skills@eurocarsplus]

[Jrh5r]

[Jrh5r]

[kreemoweet]

[Abscate]

The front and back are nearly hydraulically independent.

They are not mechanically independent and are in fact mechanically linked.
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