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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Tue Jul 17, 2018 8:39 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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I do have a hard copy of the Bentley which I’ve been using for this.
If I adjust the brakes up tight then the pedal does rise higher. The parking brake is currently slack because I was waiting until I could confirm everything else was set correctly.
I don’t have enough jars or hoses right now to do the gravity bleed like that. Could I gravity bleed each point individually? How long do you have to leave it for? |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50333
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Posted: Tue Jul 17, 2018 11:22 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
I do have a hard copy of the Bentley which I’ve been using for this.
If I adjust the brakes up tight then the pedal does rise higher. The parking brake is currently slack because I was waiting until I could confirm everything else was set correctly.
I don’t have enough jars or hoses right now to do the gravity bleed like that. Could I gravity bleed each point individually? How long do you have to leave it for? |
Yes you can do each corner individually or you can do one front and one rear at the same time. You have to baby sit the brake fluid reservoir when doing this so that you don't run out of fluid. Do several minutes on each corner or until any bubbles stop. |
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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Sun Jul 29, 2018 5:39 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Well, I’ve had no success with the gravity bleeding. I decided to try and bleed the master cylinder again.
I took off the inlet line into the rear brake pressure regulator and tried to bleed it from there, because that is a direct line from the master cylinder. The brake fluid just poured out without me pressing the brake pedal at all and would have continued until both reservoirs were empty. Is that correct? My assumption was that, after some fluid from the line had come out, no more fluid would get past the master cylinder until I pressed the pedal. In which case, the master cylinder must be defective or maybe I have rebuilt it incorrectly. |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3897 Location: Seattle, WA
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Posted: Sun Jul 29, 2018 6:49 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
... maybe I have rebuilt it incorrectly. |
Ah, the truth comes out. Your first posts indicated you had a "new" m/c. Fluid should not be "pouring" out. Usually, it will slowly drip
as fluid makes it way past the compensating ports (very tiny) and out to the lines. If the rubber cups you used are shrunken and hard (which would be
expected in an antique NOS rebuild kit), fluid might be "pouring" past them thru the equalization ports drilled thru the piston.
That scenario would also explain why you can't get a hard/high pedal, as fluid will be bypassing the cups. _________________ '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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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Mon Jul 30, 2018 3:38 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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I’m so confused. I replaced both of the bungs, if you go back in the thread you will see the photos I showed of the new bungs. I guess they must be the wrong type?
I know it’s a long thread, so not everybody will keep up with the order of things. I bought a new master cylinder and fitted it. I later removed it, took apart, cleaned it out and rebuilt it using brake fluid and the ATE rebuild paste. I didn’t use a rebuild kit. I did this purely to ensure there was no crap inside it. |
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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: Mon Jul 30, 2018 9:42 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Have you verified the push rod adjustment???? |
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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Mon Jul 30, 2018 4:31 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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I was satisfied that it was correct but I think I will disconnect the master cylinder from the servo and see if the flow stops. If it does, I guess we can assume that the push rod is holding open the master cylinder. If it doesn’t, then I guess I’ve got to dismantle the master cylinder again. |
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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Sat Aug 04, 2018 4:51 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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I tried to do the procedure I described in the previous post but it didn’t seem to have much of an effect, which suggests that the push rod was not causing the issue.
I dismantled the master cylinder and checked to see if I’d rebuilt it correctly. Everything looked to be in the correct order so I assumed I’d rebuilt it correctly. I’ve now packaged up the master cylinder and sent it back for a replacement. Let’s hope the next one is not faulty. Is there a way of bench testing a master cylinder?
Here’s some photos of the internals of the master cylinder, laid out as they were inside the master cylinder before I removed them. If anyone can see the cause of the problem, it might be useful to know for future reference.
Varga servo master cylinder internals:
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3897 Location: Seattle, WA
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Posted: Sat Aug 04, 2018 12:03 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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There's nothing obviously amiss with your m/c. The parts are a little different from the internals of the Varga m/c
I have (over 20 yrs old). An internal m/c leak is the most likely cause of a persistently mushy or too-low pedal
after shoes have been adjusted and reasonable effort put into bleeding.
I've never understood the difficulties people sometimes have bleeding the brake system. Just last week, I had the m/c out and brake lines
open to the air for a couple days. The reinstalled m/c "self-bled", i.e. just about all the air bubbled all by itself up into the reservoir and then
up the tube and out the refill reservoir. (I think the bus has to be fairly level for that to happen). A few pedal pumps discharged from each
wheel cylinder, and it was good to go. The Bentley manual says the bleeder (if there is one) on the pressure regulator should under no
circumstances be used to bleed the brake lines. Don't ask me why!
As far as checking the booster pushrod-to-m/c clearance, I don't think you need to measure anything: if there is interference, the m/c (without seal
ring installed) will not sit flush on the booster without pushing on it. If it does, you can conclude the clearance is zero or greater. Excessive clearance
doesn't seem to be a real possibility with the boosters available nowadays. _________________ '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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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Mon Aug 13, 2018 9:16 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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OK so, I have fitted the replacement master cylinder and the problem persists.
PLEASE HELP!
When the brakes are slammed on, the camper just slowly comes to a stop. The pedal is soft and the brakes begin to work after about 2 inches of pedal travel, when the pedal hardens up a bit. The pedal travel is almost all the way to the floor - about two inches from the floor.
If the rear brake shoes weren't adjusted high enough, would that provide this poor braking performance? I was under the impression that these buses would stop somewhat effectively even with just the front disc brakes.
I think there is a possibility that the clearance between the push rod and master cylinder is now too large, and the brakes aren't engaging quickly enough. However, surely the brakes would still be fully functional when doing an emergency stop - but they're not.
Any ideas? |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3897 Location: Seattle, WA
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Posted: Mon Aug 13, 2018 12:50 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
When the brakes are slammed on, the camper just slowly comes to a stop. The pedal is soft and the brakes begin to work after about 2 inches of pedal travel, when the pedal hardens up a bit. The pedal travel is almost all the way to the floor - about two inches from the floor. |
This sounds like like your front (disk) brake circuit is not working. Rear brakes alone, especially if the shoes are maladjusted, will not give you brakes that are
what I would call "somewhat effective".
An inoperative booster will give similar lousy braking, but the pedal travel will remain normal, at least if there's "normal" clearance at the M/C piston.
Maybe you have both these problems at the same time? I suppose you could test for booster operation by disconnecting (and plugging) the vacuum line to
the booster to see if it makes any difference. _________________ '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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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50333
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Posted: Mon Aug 13, 2018 1:06 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
Well, I’ve had no success with the gravity bleeding. I decided to try and bleed the master cylinder again.
I took off the inlet line into the rear brake pressure regulator and tried to bleed it from there, because that is a direct line from the master cylinder. The brake fluid just poured out without me pressing the brake pedal at all and would have continued until both reservoirs were empty. Is that correct? My assumption was that, after some fluid from the line had come out, no more fluid would get past the master cylinder until I pressed the pedal. In which case, the master cylinder must be defective or maybe I have rebuilt it incorrectly. |
I don't know what your definition of pour is, but you should get a steady stream UNLESS YO push on the pedal at which point you should get a goodly squirt and then the flow should STOP except for minor dripping.. I would recommend bleeding the front caliper through the upper bleeder if there are two, loosening off the parking brake cable fully, and then adjusting the rear brakes up tight and seeing what the pedal feels like. It should be high and hard if you have no air in the system anywhere. |
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Westfalia73 Samba Member
Joined: June 07, 2016 Posts: 121 Location: New Zealand
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Posted: Mon Aug 13, 2018 1:39 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
OK so, I have fitted the replacement master cylinder and the problem persists.
PLEASE HELP!
When the brakes are slammed on, the camper just slowly comes to a stop. The pedal is soft and the brakes begin to work after about 2 inches of pedal travel, when the pedal hardens up a bit. The pedal travel is almost all the way to the floor - about two inches from the floor.
If the rear brake shoes weren't adjusted high enough, would that provide this poor braking performance? I was under the impression that these buses would stop somewhat effectively even with just the front disc brakes.
I think there is a possibility that the clearance between the push rod and master cylinder is now too large, and the brakes aren't engaging quickly enough. However, surely the brakes would still be fully functional when doing an emergency stop - but they're not.
Any ideas? |
Maybe time to stop with the DIY approach and take it to a brake shop/garage.
Get a professional to take a look, brakes are very important and you are having no luck with it, props for what you have done, tried so far, just my 2 cents.... _________________ 1973 tintop westfalia weekender.
1973 beetle.
1981 Brazilian baywindow kombi. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Aug 13, 2018 2:05 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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did you look inside the master to be sure that there are no pits (usually dark spots) where the fluid can bleed around the seals?
Did you try pressure bleeding the system? They are inexpensive and do an outstanding one person job.
Is the bus pretty level? if it is not level the rear system will not bleed properly and air will stay in that part of the system. The reason is the bus may think you are in a nose dive and divert fluid in the proportioning valve. Did you bleed the proportioning valve? The early valve has a separate bleeder on it. The brakes should be rock hard until you start the engine if they are properly bled and the booster is exhausted of vacuum. _________________ “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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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Wed Aug 15, 2018 7:45 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Thanks for the suggestions guys. I replaced the master cylinder and this one is behaving exactly the same, so I will assume that neither of them were faulty.
Whenever I bleed the bus, I do it on level ground. I noticed that the right rear brake bleeds extremely slowly until I bleed the pressure regulator. After that, the right rear will bleed normally. I'm not sure why this is.
I now realise that I may have purchased the wrong master cylinder grommets. Some retailers, apparently including Volkswagen themselves, list 211-611-817/A as the correct part for all Transporters 1967-1979 (7mm ID, 18mm OD). However, some retailers only list that part for the non-servo buses. They list 357-611-817 for servo buses 1971-1979 (12mm ID, 22mm OD). This is obviously a much more recent part number, so I'm not sure what the situation is here.
If I have fitted the smaller bungs and the seal isn't perfectly tight, could this cause the brakes to be soft? Technically, the grommets are on the gravity-feed side of the braking system, so I've been told it wouldn't make a difference. Providing you're not leaking brake fluid, it isn't a problem if the seals don't fit tightly. However, my concern would be that air is entering the system.
Does anybody know more about this situation?
Here is an example of a British retailer who lists both grommets:
Grommet for non-servo buses (211-611-817/A)
https://www.justkampers.com/211-611-817-a-master-c...-1979.html
Grommet for servo buses (357-611-817)
https://www.justkampers.com/357-611-817-brake-rese...-1992.html |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3897 Location: Seattle, WA
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Posted: Wed Aug 15, 2018 12:15 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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I think JK is confused. It also is not clear exactly what is being measured. The OD of the reservoir nipples is 8.4 mm, and the ID of the
m/c bores where the reservoir nipples is inserted is approx 18 mm with an entrance lip of 15 mm. Therefore a bung with (uninstalled) ID
of 7 mm and OD of 18 mm is exactly right. That is what my genuine ATE bungs measure, and they fit perfectly. They are ATE #3.3304-1000-1.
If fluid is not leaking out, then air in not likely to be leaking in. There would have to be some sort of suction to draw air in, and there is just
the opposite, i.e. gravity pressure of the fluid.
I think your trust in m/c's not being faulty just because new, is misplaced. _________________ '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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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Thu Aug 16, 2018 11:29 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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kreemoweet wrote: |
I think JK is confused. It also is not clear exactly what is being measured. The OD of the reservoir nipples is 8.4 mm, and the ID of the
m/c bores where the reservoir nipples is inserted is approx 18 mm with an entrance lip of 15 mm. Therefore a bung with (uninstalled) ID
of 7 mm and OD of 18 mm is exactly right. That is what my genuine ATE bungs measure, and they fit perfectly. They are ATE #3.3304-1000-1.
If fluid is not leaking out, then air in not likely to be leaking in. There would have to be some sort of suction to draw air in, and there is just
the opposite, i.e. gravity pressure of the fluid.
I think your trust in m/c's not being faulty just because new, is misplaced. |
Is there a chance that the Varga master cylinders require different bungs from the ATE? I’m assuming that’s not the case, but I’m just spitballing.
It’s not just “JustKampers” that do this. “VW Heritage” and “Custom and Commercial” also list the bigger bung for servo master cylinders. Clearly there’s some confusion here, but I can’t understand why a mistake like this wouldn’t have already been discovered by customers who bought bungs that didn’t fit, from any of the three large distributors who sell the bigger bung.
I think the master cylinder pushrod clearance is now probably excessive so I will try and correct that next, but I don’t see how that could be the cause of the soft pedal and awful braking performance. I’ll have to examine the front brakes if that doesn’t correct the issue.
I had both of my large carjacks stolen so I now can’t raise the bus. Lovely. |
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Zed999 Samba Member
Joined: March 04, 2018 Posts: 1244 Location: UK
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Posted: Thu Aug 16, 2018 12:20 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Whereabouts in Englandshire are you Ben? |
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Ben Middleton Samba Member
Joined: April 11, 2016 Posts: 219 Location: England, UK
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Posted: Thu Aug 16, 2018 12:32 pm Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Zed999 wrote: |
Whereabouts in Englandshire are you Ben? |
Englandshire lol - I'm in the West Midlands, you? |
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Zed999 Samba Member
Joined: March 04, 2018 Posts: 1244 Location: UK
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Posted: Fri Aug 17, 2018 12:49 am Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) |
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Ben Middleton wrote: |
Zed999 wrote: |
Whereabouts in Englandshire are you Ben? |
Englandshire lol - I'm in the West Midlands, you? |
20 miles North of Liverpool. Thought you might be in Liverpool as someone nicked your jack, then I'd have offered to come and have a look. W. Midlands is a bit far.
99.9% of the time a soft pedal is air in the system and pumping them up is loosely adjusted shoes. Yep, I know you know that, but I'd go round it all again anyway. The reservoir/mc bungs are a red herring IMO. If they were bad enough to cause your problem I think they'd weep all the time. Good luck. |
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