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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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 Posted: Sun Jul 24, 2016 5:50 pm Post subject: Occasional soft brake pedal- 1970 drum brakes |
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This is what I found in my search:
This was interesting, but not really my problem:
https://www.thesamba.com/vw/forum/templates/subSilver/images/icon_minipost.gif
This seems a bit closer, but my problem is just once, or perhaps occasional:
https://www.thesamba.com/vw/forum/templates/subSilver/images/icon_minipost.gif
* 1970 Type 1, all stock suspension and parts. Probably some aftermarket stuff in there by this late date.
 Problem: Usually good braking. Two days ago I experienced sudden very soft pedal, glides to floor at moderate rate with little braking effort. Pumping up brakes did nothing, and they would not get firm. Needed to be on the parking brake to come to complete stops. I note there are no visible leaks and the MC reservoir remains full. I look underneath at all four tires and do not see brake fluid streaking. No drips under the MC.
I get back from my trip, expecting to see brake fluid puddled up somewhere under the car. Nothing.
Get in, drive away and brakes work fine all the way home (roughly 23 miles).
 Does this indicate a failing MC? |
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Joey
Samba Member
Joined: August 12, 2005
Posts: 5366
Location: Nova Scotia - Canada
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| Posted: Sun Jul 24, 2016 5:59 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Wasted youth wrote: |
| Does this indicate a failing MC? |
Yes.
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Joey
‘60 Kombi - '74 Bus - '79 Panel - '65 Beetle |
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BUGGED11111
Samba Member
Joined: February 03, 2006
Posts: 1819
Location: Oregon
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| Posted: Sun Jul 24, 2016 6:20 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Is your brake fluid level dropping in the reservoir? |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Sun Jul 24, 2016 6:33 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| BUGGED11111 wrote: |
| Is your brake fluid level dropping in the reservoir? |
No. Fluid remains high. |
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BUGGED11111
Samba Member
Joined: February 03, 2006
Posts: 1819
Location: Oregon
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| Posted: Sun Jul 24, 2016 6:41 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Wasted youth wrote: |
| BUGGED11111 wrote: |
| Is your brake fluid level dropping in the reservoir? |
No. Fluid remains high. |
If it's me I'd pull all the drums, checks cylinders, pads,etc. Look at it as system before buying stuff |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Sun Jul 24, 2016 6:48 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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No doubt this bug needs a full work up on the brakes. Haven't touched them much except to replace the rubber lines and one wheel cylinder, then bleed and adjust after getting it home several months ago. Daily driver though! 
No leaks, no reservoir drop... where is the fluid going?
I think Joey is right... that the MC is failing, as in letting the pumped pressure bleed back into the supply side/reservoir feed side instead of building pressure on the wheel cylinder side. Intermittent or occasional complaint may be attributed to chunks blocking a port, or a seal getting loose. Dunno, just thinkin' out loud.
Last edited by Wasted youth on Sun Jul 24, 2016 6:48 pm; edited 1 time in total |
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Cusser
Samba Member
Joined: October 02, 2006
Posts: 31361
Location: Hot Arizona
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| Posted: Sun Jul 24, 2016 6:48 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| BUGGED11111 wrote: |
| If it's me I'd pull all the drums, checks cylinders, pads,etc. Look at it as system before buying stuff |
Yes, good strategy.
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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BUGGED11111
Samba Member
Joined: February 03, 2006
Posts: 1819
Location: Oregon
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| Posted: Sun Jul 24, 2016 6:53 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Wasted youth wrote: |
No doubt this bug needs a full work up on the brakes. Haven't touched them much except to replace the rubber lines and one wheel cylinder, then bleed and adjust after getting it home several months ago. Daily driver though!
No leaks, no reservoir drop... where is the fluid going?
I think Joey is right... that the MC is failing, as in letting the pumped pressure bleed back into the supply side/reservoir feed side instead of building pressure on the wheel cylinder side. Intermittent or occasional complaint may be attributed to chunks blocking a port, or a seal getting loose. Dunno, just thinkin' out loud. |
Certainly could be a MC or brake hoses failing. They fail internally so it's another thing. I always use these type of things to look at the system. Usually saves time and hair pulling. |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Sun Jul 24, 2016 7:17 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| BUGGED11111 wrote: |
| Wasted youth wrote: |
No doubt this bug needs a full work up on the brakes. Haven't touched them much except to replace the rubber lines and one wheel cylinder, then bleed and adjust after getting it home several months ago. Daily driver though!
No leaks, no reservoir drop... where is the fluid going?
I think Joey is right... that the MC is failing, as in letting the pumped pressure bleed back into the supply side/reservoir feed side instead of building pressure on the wheel cylinder side. Intermittent or occasional complaint may be attributed to chunks blocking a port, or a seal getting loose. Dunno, just thinkin' out loud. |
Certainly could be a MC or brake hoses failing. They fail internally so it's another thing. I always use these type of things to look at the system. Usually saves time and hair pulling. |
Hope it's not the hoses. Replaced them new in May. |
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birddog1
Samba Member
Joined: March 11, 2006
Posts: 952
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| Posted: Sun Jul 24, 2016 7:27 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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I have 3 bugs in my family. I also have an ever growing list of recently installed parts that failed. It's actually getting to the point they're the first thing I suspect.
Not saying it is or isn't the issue but I wouldn't exclude a recently installed part as the issue. I would go with Bugged's approach but it's your time and money. If you took it to a good VW shop, that's exactly what they would do at $85+ an hour |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Sun Jul 24, 2016 7:59 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Seems to me my time and money will go more efficiently if I put it up on jackstands and check the whole system. Might as well... Changing out a suspected MC is not a five minute task. So yeah, probably dig deep. |
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enjoyther1de
Samba Member
Joined: December 19, 2010
Posts: 1279
Location: chino,ca
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| Posted: Sun Jul 24, 2016 11:32 pm Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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| Wasted youth wrote: |
| Seems to me my time and money will go more efficiently if I put it up on jackstands and check the whole system. Might as well... Changing out a suspected MC is not a five minute task. So yeah, probably dig deep. |
I had the exact problem your having. It ended up being a piece of debris clogging the brake light switch. Which later explained my spotty brake lights.
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HBB took me to BBV. |
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DeathTrap
Samba Member
Joined: February 26, 2004
Posts: 1757
Location: Sacramento/Vermont
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| Posted: Mon Jul 25, 2016 2:22 am Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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Here is your second opinion.
It is indicative of a leak in the system. Unless there is loss of fluid. It indicates a failing master cylinder. Leaking inside itself. |
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Joey
Samba Member
Joined: August 12, 2005
Posts: 5366
Location: Nova Scotia - Canada
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| Posted: Mon Jul 25, 2016 7:20 am Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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The old MC in my '74 bus worked fine if you applied firm pressure to the pedal... but if you gently pushed on the pedal it would go right to the floor.
Brake fluid is getting by the seals/cups.
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Joey
‘60 Kombi - '74 Bus - '79 Panel - '65 Beetle |
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TheRustySuper
Samba Member
Joined: June 24, 2009
Posts: 2076
Location: New Albany, IN
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| Posted: Mon Jul 25, 2016 9:47 am Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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Sounds like a failing MC to me. Had your exact symptoms on my '72 Super when the original MC failed on me. No external leaks either.
Like others have said though, don't just check the master. Check out the whole system and see if there's anything else that could be your problem or contributing to it.
A few years back I replaced the soft lines on my Super. That turned into acquiring a new MC and all new wheel cylinders as all the original parts started failing one by one. Brakes are incredibly important and are often left neglected, so take your time and go through everything.
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My '72 Super |
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theKbStockpiler
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Joined: July 07, 2012
Posts: 2316
Location: Rust Belt
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| Posted: Mon Jul 25, 2016 10:17 am Post subject: Re: Occasional soft brake pedal- 1970 drum brakes |
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I'm under the impression that if a piston in a wheel cylinder or a calipar has resistance when the pressure is released they will allow air in without leaking fluid . I have had this happen with calipars. Also a slow leak at a wheel cylinder will bleed it's self. It is advisable to look under the dust boots on your wheel cylinders. If you can get a good pedal without it slowly going to the floor ;with no external leaks ,the master is good.
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My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
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