IMPORTANT brake master cylinder information!

[raygreenwood]

Damn....I hate being TOTALLY WRONG!

But on the other hand I like learning something new...especially after almost 40 years of working on these cars.
I probably could have found that others in these forums already knew this information...if I had asked or looked deep enough.

So....titan3c asked a very important question that I "thought" I was giving the right answer to.

" If the brake light switches on the master cylinder go on the top holes/ports...why do all the books show them in the bottom holes/ports?"

I said that the fluid lines to the brake cylinders should have the larger holes...obviously......and I was wrong!

My very first 411 mechanic (high school)...a genius...but obviously didn't know everything! ...had pointed out to me that the fluid ports to the wheel cylinders and calipers MUST have the greater fluid flow...and it all sounded and looked right...so I NEVER...even noted that all of the books show it the other way around.

So:

This IS the correct location for the brake light switches...in the lower holes.

Why is this?

I found this in the InterEurope shop manual. A manual that is kind of rare in the US...I have only had for about 1.5 years....and is very incomplete...but has some REAL gold nuggets of type 4 only information.

This information is NOT in the Haynes manual, the Clymer manual, the Drake book, the Chiltons....and is not in the Bentley for type 3...but I'm not sure the type 3 has this feature.

As the text notes....to keep from having to use residual pressure valves on the fluid outlet ports which can cause brake drag in some situations....they used restricted/smaller drillings in the fluid outlet ports ....to allow for faster pressure build up while bleeding the brakes.

Damn...very cool!

This is the top "restrictor" port that feeds the metal brake lines to the calipers and wheel cylinders

This is the lower port that feeds the brake light switches.

Sorry for the blue pictures....I had to use my LED light to illuminate these.

In your fluid lines and brake switches are reversed...like they have always been on my car...even before I bought it....this will NOT cause any problems with braking. It may just make bleeding a little more difficult/slow.

Since they have always been reversed on my car...and my very first mechanic also did this.....I do not feel totally alone in my misunderstanding of the system.... .

Ray

[KTPhil]

Yes, the Type 3 masters had two sized orifices to aid in bleeding:

https://www.thesamba.com/vw/forum/viewtopic.php?t=509786

[raygreenwood]

[Lars S]

Thanks Ray, we all learn from this good info!
Im not under the dash right now but isnt it quite obvouis which brake line to go to what port when you try to re fit the master.?..I remember the lines to be wery stiff...

Also I nowdays try to N O T drain the lines going to the wheels whatever I do yo the brakes...as we kmow bleeding the lines to the rear is a BIG p.i.t.a. if they have been emty...


Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[raygreenwood]

[titan3c]

This all comes at the time I am installing a NOS mc, and I was just going to start the bleeding procedure today.

The new mc had the switches on the bottom, and the old mc which came with the car when new (71 sedan) are on top. When I was installing the new mc the brake line nearest the fire wall lacked about quarter of an inch being long enough. So I took the mc out, and moved the switches to the top, and everything went well. Since I haven't got everything buttoned up yet, and haven't done the bleeding----I may just do it over, and put the Switches back on the bottom. If I remember correctly there isn't any possibility of stretching the short line. It's a real straight line to the lower connection, no bends. It would require making a short line "hook-up), or maybe I could find some kind of connection that would make up the shortage. If I had already done the bleeding I would live with it--- I'm a well known recipient of "murphys law", and use to it. So changes and corrections are not new to me. Bob

[raygreenwood]

[titan3c]

Yep, I've been thinking it over, and I think I'll just leave my installation intact the way I got it. This afternoon I will start the bleeding process, as you explained it.

As for that little tin shield-----it sure was a big help to cut that off. I cut mine off too. I'm planning on working that into a take off item like engine tin, and bolt it back on. Still can't figure out why it was there in the first place. But I'll give the engineers credit for it being there for some reason, and bolt it on

BTW Ray, That composite cover that goes underneath all of this is laying in the trunk of my car, and is in good condition, not perfect but real good. If you need it for mold pattern we'll work out a way to get it to you. Bob

[raygreenwood]

Funny you should mention that cover. I was working that one....and the valance in the rear window over in my head....again....this past weekend.

I already know how to mold them.....and funny enough....the mold will either be high eensity plaster or fine portland cement....or a combination.

The issue I have been working over is what to make these parts from.....fiberglass, casting resin etc.....will all warp in the heat.

I see why they made them from cast cardboard....but they need to be a little tougher.....and coated for water resistance.

I have decided to make the first one.....from heavy aluminum foil. Like twice the thickness of store bought heavy aluminum foil. About 5-6 layers with a thin layer of sprayed bedliner in between. I will then put a spray texture on the outside. The texture will be slightly different from factory.....but will look professional. Ray

[titan3c]

Awwright, that sounds great. I'm looking forward to the results. When I think of molds I think of pouring something in them. But there are press dies or molds too. I'm not an expert on the proper material for particular uses, as an metallurgist like you. That rear window part will sure make an improvement on the inside appearance, and so will the other one. Bob

[lofoxx]

If I should post a new thread, by all means, let me know - figured this was active and somewhat relevant. Bought a master cylinder for my 411, installed, and it seems the seals are rather corroded... it barfed brake fluid all over the place. Any thoughts on options for a better master? Or a custom master install?

Thanks in advance, guys.
Loren
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1972 VW 411

[raygreenwood]

[lofoxx]

1. was this an NOS master cylinder, used or rebuilt? (NOS, but just old...)
2. What brand and do you have any pictures of the packaging? (ATE
411 611 015B - I don't have the box at the moment)
3. What do you mean it barfed brake fluid everywhere....from where? (From the master)
4. Yes....the other thread I listed is about alternate master cylinders and other modifications.

Thanks Ray!!! Seems like it might be a good option just to customize rather than keep going after old borked parts...

Thanks!
Loren
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1972 VW 411

[raygreenwood]

[titan3c]

Just a couple of technique questions: How to remove the reservoir connections on top of the mc. And how to put pressure on the push rod spring when removing the clip ring to keep innards from flying out, perhaps hitting you. This may sound silly, but I've never done this, and I can see the possibility of a ooops. Bob

[raygreenwood]

[raygreenwood]

Titan3c........I know you are trying to get your car back on the road.

So aside from bleeding attempts it sounds like the NOS cylinder may have had the "old seal cup" syndrome.

This does not make it a bad deal ....just temporarily useless. It should have a nice clean bore and no oversize issues and clean pistons and hopefully clean flap valves.

If you want......you can send it to me to put seals in it for youm I have three seal sets and can get it together in about an hour or two and have proper brake paste and a few little tools for putting the seals on and a good bit of practice.

I will post how to make a little "spoon" that really helps to get seals on without damage.....in lieu of the unobtanium tapered sleeves like the factory manual shows.....but its still a b*tch.

The seals only ran me $3 a set so no charge. I can use yours to photograph for the how to. Ray

[titan3c]

OK---sounds good to me. I could send the nos or the old one or both. You might find the old one interesting since it has been in the car since new. Use the PM for mailing instructions if you wish. Bob

[lofoxx]

Hi Ray,

What are the chances I could send you a master cylinder for my '72 411 for you to rebuild? Can't find a kit to save my life... the car is ready to roll outside of this piece.

Thanks in advance,
Loren
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1972 VW 411

[raygreenwood]