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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Tue Jan 12, 2021 4:10 pm Post subject: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Hello all,
After buying our bus in April '20, we replaced the rear shoes and cylinders and bled the system. Front pads seemed fine, as did hoses. We have driven the bus many miles since then with the brakes working well. My daughter took the bus to visit a neighborhood friend and reported that the brakes faded almost all the way to the floor. She was able to pump the brakes to stop. However, after the pumping the brakes were fine again.
On her return, I took the bus for a test on the exact route, no issues and the brakes were fine there and back. I also tested the booster by pressing the pedal while starting and, as expected, the pedal dropped slightly - but settled well over half the available travel, as its always been. Fluid is full with no apparent leaks.
Any ideas why seemingly good brakes would intermittently fade?
Thanks! _________________ 1976 VW Transporter, 2.0 FI Engine |
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mike77777 Samba Member
Joined: May 13, 2009 Posts: 119 Location: portland or
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Posted: Tue Jan 12, 2021 4:16 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Your Master cylinder could be the problem. _________________ patience and putty |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3899 Location: Seattle, WA
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Posted: Tue Jan 12, 2021 5:29 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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wagohn wrote: |
... but settled well over half the available travel, as its always been. |
Hmm, wonder what that means? Normal braking action starts as soon as free play at pedal is taken up, and just
increases in force as pedal is pushed further down. It certainly does not drop halfway, which would sort of
suggest one of your brake circuits is kaput. Something that requires immediate attention, at any rate. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
Stop dead photo links! Post your photos to The Samba Gallery! |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Jan 12, 2021 5:31 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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master cylinder _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51153 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Tue Jan 12, 2021 5:46 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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kreemoweet wrote: |
wagohn wrote: |
... but settled well over half the available travel, as its always been. |
Hmm, wonder what that means? Normal braking action starts as soon as free play at pedal is taken up, and just
increases in force as pedal is pushed further down. It certainly does not drop halfway, which would sort of
suggest one of your brake circuits is kaput. Something that requires immediate attention, at any rate. |
X2, good brakes should only go down less than 2" no matter how hard you push with the engine running, you might have more than one issue going on. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Tue Jan 12, 2021 6:19 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Thanks everyone - perhaps "halfway" down was too pessimistic, probably closer to 15-25% before we get pushback. Brakes have always been excellent since we refreshed the shoes/rear cylinders. Stops on a dime.
As for the original question, thank you! Makes total sense that if the seals in the MC were on their way out that the odd "no pressure" scenario would occur.
We will order a new MC as I know my limitations and don't fancy refreshing the old. Any tips for the removal/install? I see references to bench bleeding in other threads but I'm not sure what that entails. I'm assuming filling the MC with fluid before install - wouldn't the fluid just pour out when unplugging the holes to fit the pipes? I'm assuming the MC can just be swapped out without any mating to the servo issues?
Thanks! _________________ 1976 VW Transporter, 2.0 FI Engine |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3899 Location: Seattle, WA
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Posted: Tue Jan 12, 2021 7:42 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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wagohn wrote: |
We will order a new MC as I know my limitations and don't fancy refreshing the old. Any tips for the removal/install? I see references to bench bleeding in other threads but I'm not sure what that entails. I'm assuming filling the MC with fluid before install - wouldn't the fluid just pour out when unplugging the holes to fit the pipes? I'm assuming the MC can just be swapped out without any mating to the servo issues? |
There isn't really a prospect of "refreshing" the M/C, as rebuild kits are not available. I've never had the slightest trouble bleeding system with new M/C with no
"bench bleed" involved. After install and filling the reservoir, air in M/C will just naturally bubble up and out (assuming bus is level, and not at some weird angle).
Rarely, the internal pushrod in booster will be too long to suit the M/C, causing the M/C compensating port to be blocked with resulting eventual brake lockup.
You can somewhat feel that happening by just holding M/C (sans o-ring seal) onto booster in installed position. You should feel no resistance from booster pushrod
in doing so.
Inside of booster should be checked for leaked brake fluid, and cleaned out if present - not too easy if installed.
Take it easy when manipulating metal brakelines, as they will kink all too readily. The metal lines have to be aligned almost perfectly to be able to start the nuts, and
sometimes takes a deal of fiddling to get it right. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
Stop dead photo links! Post your photos to The Samba Gallery! |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Tue Jan 12, 2021 9:36 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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kreemoweet wrote: |
There isn't really a prospect of "refreshing" the M/C, as rebuild kits are not available. I've never had the slightest trouble bleeding system with new M/C with no
"bench bleed" involved. After install and filling the reservoir, air in M/C will just naturally bubble up and out (assuming bus is level, and not at some weird angle).
Rarely, the internal pushrod in booster will be too long to suit the M/C, causing the M/C compensating port to be blocked with resulting eventual brake lockup.
You can somewhat feel that happening by just holding M/C (sans o-ring seal) onto booster in installed position. You should feel no resistance from booster pushrod
in doing so.
Inside of booster should be checked for leaked brake fluid, and cleaned out if present - not too easy if installed.
Take it easy when manipulating metal brakelines, as they will kink all too readily. The metal lines have to be aligned almost perfectly to be able to start the nuts, and
sometimes takes a deal of fiddling to get it right. |
Thank you, sir. Some great info here. _________________ 1976 VW Transporter, 2.0 FI Engine |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3899 Location: Seattle, WA
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Posted: Tue Jan 12, 2021 11:09 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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I might add to suggestions that some very experienced air-cooled vehicle buffs recommend taking apart
brand-new brake cylinders to clean out factory debris. I've never done so, and not been stung. Yet. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
Stop dead photo links! Post your photos to The Samba Gallery! |
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ToolBox Samba Member
Joined: January 27, 2004 Posts: 3439 Location: Detroit, where they don't jack parts off my ride in the parking lot of the 7-11
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Posted: Wed Jan 13, 2021 10:16 am Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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wagohn wrote: |
I'm assuming the MC can just be swapped out without any mating to the servo issues?
Thanks! |
Make sure the servo is clean and dry inside. If it's wet it might be time to premptivly send it out for a rebuild.
Your daughter experienced a hydrulic system failure. Brake fade is a whole different animal and it sucks in a whole different way. |
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Whaanga Samba Member
Joined: May 07, 2016 Posts: 630 Location: Rochester, NY
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Posted: Thu Jan 14, 2021 2:02 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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I had a similar issue a couple of years ago. I had redone the front and rear brakes and felt I had a good system. I then had a workday with Colin (Itinerant Air-cooled) and when he drove my bus, he quickly identified that I had a bad master cylinder. What was strange to me is that when I applied the brakes, I felt I had good control - but I had learned to compensate by pushing the pedal down with a quick, last-minute foot move. Colin used a slower physical approach. So - I tried changing how I applied the brake and suddenly realized that I indeed had a problem. (see the write up from Colin's website: http://www.itinerant-air-cooled.com/viewtopic.php?...d1248fd48)
I was able to source a quality master cylinder and when Colin came for his next visit, we replaced it. It was a pretty do-able job and then not soon after, the servo failed. AND - so I had it rebuilt and now - I have much more confidence in my brake system.
From my experience and what others have written, it make sense to replace your Master Cylinder. _________________ Late 1973 Bay w/a transplanted 914 Engine |
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oscarsnapkin Samba Member
Joined: October 22, 2013 Posts: 558 Location: Bucks County, PA
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Posted: Thu Jan 14, 2021 2:43 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Whaanga wrote: |
I had a similar issue a couple of years ago. I had redone the front and rear brakes and felt I had a good system. I then had a workday with Colin (Itinerant Air-cooled) and when he drove my bus, he quickly identified that I had a bad master cylinder. What was strange to me is that when I applied the brakes, I felt I had good control - but I had learned to compensate by pushing the pedal down with a quick, last-minute foot move. Colin used a slower physical approach. So - I tried changing how I applied the brake and suddenly realized that I indeed had a problem. (see the write up from Colin's website: http://www.itinerant-air-cooled.com/viewtopic.php?...d1248fd48)
I was able to source a quality master cylinder and when Colin came for his next visit, we replaced it. It was a pretty do-able job and then not soon after, the servo failed. AND - so I had it rebuilt and now - I have much more confidence in my brake system.
From my experience and what others have written, it make sense to replace your Master Cylinder. |
I was kind of away from thesamba for awhile having had twins a few years ago. I’ve been been back pretty regularly for a few months and have not seen any sign of Colin. Anyone know of his status? Hope he’s well. _________________ - 1977 CEI Sunroof Bus 2.0L F.I. Hydraulic Lifters
- 1973 Thing
"It’s so easy to laugh, it’s so easy to hate, it takes strength to be gentle and kind." |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Thu Jan 14, 2021 6:18 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Thanks all, New MC should be here tomorrow. I just soaked the brake pipe nuts in PB Blaster for the night in prep.
On a side note, I'm using newly purchased Harbor Freight 6" ramps, should have bought them years ago. Drive right on, rock solid, and lots of work room. Great deal for $45 and rated for 13000 lbs.
I'm getting older and need a little more room.
_________________ 1976 VW Transporter, 2.0 FI Engine |
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22670 Location: NYC/Upstate/ROW
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Posted: Thu Jan 14, 2021 7:46 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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Start those brake line unions before you bolt up the MC, that lets you manipulate both to line them up. I find I can feel the threads engage when I have both in hand, vs one being bolted up. _________________ .ssS! |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3899 Location: Seattle, WA
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Posted: Thu Jan 14, 2021 9:37 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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oscarsnapkin wrote: |
I’ve been been back pretty regularly for a few months and have not seen any sign of Colin. Anyone know of his status? |
He's taken the year off from his usual activities, as many of us have. He still posts (infrequently) on his website: https://www.itinerant-air-cooled.com, and
just last week put up a new site banner there. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
Stop dead photo links! Post your photos to The Samba Gallery! |
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vwwestyman Samba Member
Joined: April 24, 2004 Posts: 5688 Location: Manhattan, Kansas, USA
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12728 Location: on a bike ride somewhere
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Posted: Fri Jan 15, 2021 9:34 am Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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It's been mentioned here before, but some new cylinders have the rear brake light switch mounted planar with the front switch, and that can get in the way of the handbrake cable. Good cylinders mount the switch at an angle. It's up to you if you want to try to return/exchange it, or make a chafe-guard for the cable; just look out for it!
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Fri Jan 15, 2021 9:41 am Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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airschooled wrote: |
It's been mentioned here before, but some new cylinders have the rear brake light switch mounted planar with the front switch, and that can get in the way of the handbrake cable. Good cylinders mount the switch at an angle. It's up to you if you want to try to return/exchange it, or make a chafe-guard for the cable; just look out for it!
Robbie |
Good to know, thanks. Unfortunately, delivery seems to be end-of-day, then a prior commitment tomorrow. I intend to at least remove the old one today. _________________ 1976 VW Transporter, 2.0 FI Engine |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Fri Jan 15, 2021 1:52 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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So I got the old MC off and everything came off fairly easily. The only possible issue was removing the filler tube. There appears to be a "shouldered, black rubber, inner insert at the inlet and the shoulder area is torn up or deteriorated. How crucial is this, can I reasonably use as pictured, and in the pic do I have it the right way around?
Inner booster was dry.
Thanks for your attention.
_________________ 1976 VW Transporter, 2.0 FI Engine |
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wagohn Samba Member
Joined: June 24, 2014 Posts: 740 Location: United States
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Posted: Fri Jan 15, 2021 6:15 pm Post subject: Re: 1976 Bus - Brakes Mysteriously Faded, Then Came Back - |
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I decided to go with the frayed black grommet in the pic. Other than the shoulder it was complete. I've ordered a new one and will fit when it arrives.
New MC is now on and holding fluid. Next step, bleed the brakes. _________________ 1976 VW Transporter, 2.0 FI Engine |
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