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Master Cylinder leaking Advice?? 1971 411
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mg93108
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PostPosted: Thu May 26, 2016 1:13 pm    Post subject: Master Cylinder leaking Advice?? 1971 411 Reply with quote

So the master cylinder is leaking on our 1971 411.
I have no idea where to start.
I'm not even sure from where it is leaking.
Good anyone please provide me with some step-by-step instructions?
I would greatly appreciate it!!!
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raygreenwood
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PostPosted: Thu May 26, 2016 2:18 pm    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

OK....all of this assumes that you have not been up under the dash working on anything like the metal lines or the brake light switches....meaning no chance that you have left something loose or damaged something.... right?

So...I assume you KNOW its the master cylinder leaking because its getting all over your feet, carpet and running down the pedals...right?

So....

1. 90% of the time the master cylinder leaks at the pushrod end due to the primary outer circuit shaft/piston seal either deteriorating with age....or more commonly....damaging itself due to a rust ridge at the outer opening of the master cylinder.

IMPORTANT NOTE: Does your car have any pesky little water leaks around the window or windshield seal? Do you live in a rainy humid area with wide ranges of temperature swings?

If so....the most common cause of the rust ridge on the outer opening of the cylinder is two fold. First all master cylinders leak a VERY tiny bit....like a couple of drops...if that much....every few months. Usually it never gets out of the boot and looks more like a smear or smudge. On most cars, the cylinder is either in the engine compartment or under the car like other ACVW.
Between heat and/or air circulation.....any small smudge of leaked fluid is either dried or dissipated.

However, in humid areas...with wide temperature range...or in leaky cars....being that the cylinder is under the dash...and is a large chunk of metal...in the coll rainy season or in a leaky car...water condenses all over the cylinder which is why even and especially under the dash...the cylinders get a hideous rusty look.
The brake fluid smear is hygroscopic....it absorbs water like its supposed to. If you catch it early...it looks like a whitish pasty ooze. Many mistake it for assembly lube.
But...now it cannot evaporate and its highly corrosive. It eats up a ring right up to the edge of the cup seal.

2. About 5% of the time you may find one of the brake light switches has a crack in the plastic center section and is sweating fluid. Its rare...probably less than 5%

3. In rare cases...5% or less....either the top fluid fill tubes have a rotted grommet seal where they enter the cylinder or may be leaking from the master cylinder reservoir....rare.

First you need to either locate a rebuilt cylinder...or a kit to rebuild yours (if its rebuildable)...about 50/50.

Or...you could find a rebuild kit.....opt to never have this happen again...and just pay the cost to have it stainless steel sleeved.

http://www.brakeandequipment.com/

http://www.karpspb.com/sleeving.htm

http://www.applehydraulics.com/brakes.htm

All of these companies sleeve brake cylinders for a living. The cost is usually about $100-150. If your pistons are in good shape...no corrosion under the brass flap valves....a simple rebuild kit for $25 and having the cylinder sleeved and it will last you until you die...maybe with just a new seal kit every 50k miles....but the cylinder will last forever.


There are other options but that is a different conversation.

I would use a syringe and pull all the fluid from the reservoir. Then if you still have the cardboard underdash steering column cover...remove the two screws that hold it up.

NOTE: if your cardboard cover is complete...pull it off and keep it safe and I will ask to borrow it to make a mold in the next 6 months so I can offer these to the community...made of aluminum or steel.

On the right side of the pedal cluster you will see the master cylinder. Pull the brake light three prong connectors off. Pull the carpet back. Put a sheet pan under the pedal cluster on the floor.

There is no un-messy way to do this. If you have small hands and can reach up on top of the master cylinder...with a small cup in hand...pull the blue hoses off one at a time and drain them into the cup.

You can also drain them into a soft terry cloth rag.

Then with a flare wrench...remove each brake line. I procure small rubber caps from a FLAPS to cover the end of each line right as they come loose to keep leakage down and air infiltration low. Use soft terri cloth rags under the fittings to absorb what leaks out.

Now take a 19mm socket and unbolt the two master cylinder bolts. The master cylinder pulls forward and it comes out.

Disassembly is like any other master cylinder.

Get to this stage and show us what you got and I will advise.

WARNING...DO NOT BUY NOS MASTER CYLINDERS. They are too old and will fail quick if they work at all.

At Rockauto they list a Centric brand (not bad) cylinder but list out of stock right now.

If your seal is just shot but the cylinder is fine, you can buy a Bendix type 3 master cylinder rebuild kit for $19.34 at rockauto.com.

For that price, it should just have the seals (cups) brass flap valves, 2nd circuit lock screw seal washer and a new outer clip....which is ALL that is usable anyway.
The Raybestos kit they list for $25.79...has new pistons. The type 3 pistons will not work at all. different length and spacing...but all of the parts I listed above are the same and will fit. As long as your pistons do not have severe corrosion pits under the flap valves they are perfectly resusble.

Ray
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mg93108
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PostPosted: Thu May 26, 2016 4:14 pm    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

Wow!
That's a lot
Thank you very much
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mg93108
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PostPosted: Thu May 26, 2016 4:21 pm    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

Are these the same as the 914 Porsche?
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raygreenwood
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PostPosted: Thu May 26, 2016 5:46 pm    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

mike93108 wrote:
Are these the same as the 914 Porsche?


No...not even similar, Porsche 914 is 17mm. These are 19mm...and the type 4 master cylinder is totally unique to the type 4 car .

Nothing like it at all in any other ACVW. It mounts totally different. Different casting.

Also...TRUST ME....you cannot just slam in another 19mm x 60mm master cylinder even if it would bolt end. The front and rear bias are specifically set up in each car by the springs in each circuit. Great way to get killed....been there.

The type 3 balance is similar enough that it "should" work...with only a little adjustment to the rear brake balance unit....IF you could bolt it in...but you cant.

Now....IF you want to do some heavy fabrication...I am working on the under dash mod to allow installing a type 3 cylinder or power brakes like factory...meaning in the trunk instead of under the dash It requires a brcket, an adjustable pivot unit and another pushrod, a flange and drilling out the stamping into the trunk.

For now your best best is to simply rebuild yours if it can be rebuilt. You can use the seals and flaps...ONLY...from a type 3 kit. Ray
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titan3c
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PostPosted: Fri May 27, 2016 8:09 am    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

Ray, my cardboard cover is in good shape, and I have it off now. I have made some simple repairs on it around the screw holes, but don't think that is anything that would be a problem for you.

Getting it safely to you would be the challenge. Bob
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raygreenwood
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PostPosted: Fri May 27, 2016 9:26 am    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

titan3c wrote:
Ray, my cardboard cover is in good shape, and I have it off now. I have made some simple repairs on it around the screw holes, but don't think that is anything that would be a problem for you.

Getting it safely to you would be the challenge. Bob


Put it someplace safe and dry....I will make a box for it and ship it to you to ship to me in the next three weeks.

During the mold making process...so I do not destroy your original....I will restore it. I will do any patching of small dents and holes with wood glue and powdered cork. Then fix the little texture spots.

Then seal it with several coats of matt urethane...then spray it a satin black with Plasti-coat. Basically it will be waterproof.

Then...I will make a two part mold of either plaster or concrete.

The object here for me....is really the shape.
I also have the rear valance for a two door/four door that I am doing the patching work on now that was sent to me five years ago.

I do not want to recast these in a mulched cardboard again like they are. They will not last. I have explored MANY manufacturing methods and materials. Only a few of the most difficult ....and expensive....would make a part that really lasts.

And....the factory texture usually gets damaged over time and wherever you patch it the texture is flawed. So....its so simple to put on an acceptable texture after the fact.

So...the best way I have found I think...is to make a stiff hard, shape only mold. I will use the top and bottom to pressure shape sheets of .016" aluminum sheet. Then spray a layer of rubberized coating...let it dry and press the second sheet.

Spray a second layer of mastic and press the two together. This should yield parts That are in the .040" to .045" thick range with an accurate shape that will not change with heat and moisture. If I dont like the strength I could go to three layers.

The texture can be simple generic...meaning one of the satin texture paints....or I can nearly duplicate the factory pattern with industrial flocking.
Ray
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titan3c
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PostPosted: Sat Mar 25, 2017 7:02 am    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

Ray, I guess we got off the subject some how, but I still have the underneath cover off my car. You mentioned how to mail it to you so you could make a mold, but haven't heard anymore since. Also I'm still very much interested in that rear window trim you were working on. Bob
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raygreenwood
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PostPosted: Sat Mar 25, 2017 8:32 am    Post subject: Re: Master Cylinder leaking Advice?? 1971 411 Reply with quote

titan3c wrote:
Ray, I guess we got off the subject some how, but I still have the underneath cover off my car. You mentioned how to mail it to you so you could make a mold, but haven't heard anymore since. Also I'm still very much interested in that rear window trim you were working on. Bob


I was just working this one through my head again yesterday. I cannot make the mold until warm weather comes so I have amonth or so if I am going to get to it in relative order.

The two parts that need molding are the under dash cover and the valance for the rear window.
I am working on what to cast or mold the parts from. There are several combos I am exploring still.
Again...shape and longevity is everything...texture and color is secondary as that can be easily aplied after molding.

I have not forgotten you and will get back on this soon. Ray
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