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  #1  
Old 09-06-2015, 04:55 AM
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Car wouldn't STOP!!

Hello, just had a really traumatizing experience about an hour ago. So i have a 1963 220Sb 4 speed column shift, Anyways i took my car out this morning for a nice drive and it was great but I decided to go to the store about an hour ago (at night). So i go for a drive and pass a few blocks then i come across a busy red light and as i start to brake the car doesn't brake at all! and the light is still red and i slowly pass the light and as i come to the middle of the intersection trying to brake, the light turns green and i go a few blocks then turn back and go home. All of this is happening while listening to Patsy Cline which makes it even more of a movie death scene... The brakes were great until now because the PO rebuilt them. I don't know why this happened but its very dangerous. I changed the brake booster lines a few weeks ago because the car stalled because of a small vacuum leak. anyways any ideas whats going on. Just to clarify my brakes work fantastic all the time except for this one situation. Also my reverse is really hard to get into! thanks in advance.
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  #2  
Old 09-06-2015, 09:19 AM
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If the pedal dropped very low , this is a sign of a bad master cylinder.

Look for a cut away pic of one on the net. The rubber seals have a lip on them that faces the pressure side. As the seals wear, the lips are not under as much compression and will leak ( internal to the MC ) . This causes loss of braking pressure.

Why are the brakes seemingly OK now? If the pedal is pressed rapidly the lips fan out and are pushed into the cylinder walls making for a good seal.

The easy way to test a MC is to place your foot lightly on the brake pedal and as it falls keep following. If the MC is leaking internally the pedal will slowly fall to the floor. Sometimes in the early stages of failure you need to drive on a slightly bumpy road to generate some vibration,

How many lines do you have coming out of the MC? If only one it is a really good idea to convert to a dual circuit master cylinder. This will at least give you 1/2 braking if something fails.

If you do have a dual circuit MC , you still had 1/2 braking ( front or rear ) and a very low hard pedal.

If the pedal remained high and was hard to press, you have a brake booster / vacuum supply problem. In that case pressing harder would have stopped the car.
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Old 09-06-2015, 09:39 AM
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I vote for master cylinder also.

Regarding converting to dual circuit MC, doesn't that involve very extensive fabrication of brake lines? And a different power booster?

I have a 63 220S and am interested in all of this, but I've heard that swapping to later master cylinder involves metal fabrication on the firewall..
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Old 09-06-2015, 12:54 PM
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I don't know the specifics of these cars but will say that metal work around the master cylinder / booster area is preferable to performing metal work ahead of the front wheels. . . .. .

In order to make the conversion, one must study last generation single and first generation dual circuit setups. If the same or similar body series was available in both version, it is a simple parts swap even if that entails cutting metal.

Also study other cars regardless of brand that use the same brake booster type. It does not need to be the same exact booster as things like master cylinder mountings / brake booster mountings tend to stay similar and auto makers rarely make their own brake parts.

Lucas , Girling and ATE are common Euro brake makers.
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Old 09-06-2015, 01:20 PM
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My recollection is that the master cylinder and booster mount together on the later cars with dual circuit brakes and that the firewall sheet metal is different. On the earlier cars the master is mounted on the firewall (in a different spot) and the booster is remote mounted in front of the left front wheel. Both are ATE.
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  #6  
Old 09-06-2015, 01:53 PM
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That would be very unnerving. Did you have time to try to grab the e-brake?

When I replaced my MC, I kept it original. As long as you have good components and keep the fluid changed regularly, it should work well. One thing on my car though is after an instance of hard braking, I have to "pump" the brake pedal a little bit to build pressure back up. If I don't, the pedal travels far before the brakes engage and that can be a bit of an unwanted surprise. I don't know what exactly it is but I had the brake booster rebuilt twice. It's just a quirk of the car, I guess.

I should complete the brake system rebuild by doing the calipers/wheel cylinders, but they don't leak.
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  #7  
Old 09-06-2015, 05:24 PM
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Quote:
Originally Posted by ScooterABC View Post
My recollection is that the master cylinder and booster mount together on the later cars with dual circuit brakes and that the firewall sheet metal is different. On the earlier cars the master is mounted on the firewall (in a different spot) and the booster is remote mounted in front of the left front wheel. Both are ATE.
This is sounding like a remote power brake system that some 60's British cars and large 70"s USA trucks used. The master on the firewall sends pressure to a slave cylinder in the booster , the booster from the slave forward is similar in function to a firewall mounted booster / master.

Dual circuit could be added to the remote booster and the single circuit to the firewall retained.

Looking towards the street rod world may offer another solution. The single and dual diaphragm units they speak of only have to do with how much pressure the booster will generate.

Remote Mounted Brake Boosters: Vacuum Booster Solutions For Cramped Engine Compartments | Master Power Brakes
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Old 09-07-2015, 12:18 AM
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Old 09-07-2015, 12:23 AM
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Here are the pictures. The brakes look good but I guess I have to change the MC from you guys are saying. So is this a dual or single? Also I am planning on taking my car to the shop. Will changing the MC most likely fix my problem? Thanks
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  #10  
Old 09-07-2015, 07:53 AM
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Quote:
Originally Posted by Project Grandslam View Post
Also I am planning on taking my car to the shop. Will changing the MC most likely fix my problem? Thanks
If you're planning on driving the car to the shop following the "no brake" episode, changing the MC will likely be the least of your problems.
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  #11  
Old 09-07-2015, 08:55 AM
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The MC looks to be a single circuit system since all lines attach at the left side. It has 2 lines maybe 3 of the one that loops over is connected to the bottom. This isn't typical for a remote booster. I'd need to see a diagram to go farther.

Fitting a firewall mounted brake booster would require an extension to get the booster beyond the clutch MC and relocation of the battery to the trunk.

I'd also take an inventory as to what brake parts have been changed, the MC looks very old , calipers fresh painted , brake hoses unknown. I would not call the braking system "completely rebuilt" at this point.
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Old 09-07-2015, 08:59 AM
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Yep, it's a single circuit. I second 97 SL320, go through the whole system and update old parts. The MC looks like it's well past its prime, just from the outside, I wouldn't question replacing it since it's critical. Brake fluid in the reservoir looks really brown and nasty. Should be change annually or every 2 at most. DOT 4.

Will it solve your problems? Some of them but you may need to send out the booster for a rebuild to get everything right. Also, if your brake fluid is that old, you'll want to flush/replace the clutch fluid.
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76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6
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  #13  
Old 09-07-2015, 04:03 PM
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Ok, thanks for the input guys.
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  #14  
Old 09-12-2015, 06:22 AM
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Just to help with a diagnosis, when the brakes didn't stop, did the pedal go to the floor ?(usually a fluid leak / MC failure) or did the pedal suddenly become unresponsive & very hard to press down? (failure of the power-assist)

AS for changing to the later, dual system, to install the correct integral dual MC/vacuum-booster would require major firewall surgery, moving the battery and a different pedal assy & clutch master cylinder.
Alternately, one might be able to substitute a dual master cylinder without the booster, and plumb in a PAIR of remote vacuum servos - one for each circuit. Seen this setup on a late '60s British Rover 3500.
The longer, dual master cylinder might still require moving the battery.

Happy Motoring, Mark
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Old 09-12-2015, 08:13 AM
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Originally Posted by Mark DiSilvestro View Post
JAS for changing to the later, dual system, to install the correct integral dual MC/vacuum-booster would require major firewall surgery, moving the battery and a different pedal assy & clutch master cylinder.
Alternately, one might be able to substitute a dual master cylinder without the booster, and plumb in a PAIR of remote vacuum servos - one for each circuit. Seen this setup on a late '60s British Rover 3500.
The longer, dual master cylinder might still require moving the battery.
That's what I was trying to say but didn't know the specifics.
Well said. In other words it's a PITA.
Replace the MC and invest in good seat belts.
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