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Rear Drum Brakes Locking On (1972 Camper)
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Tcash
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PostPosted: Wed Jul 11, 2018 9:20 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Make sure you get all the old grommet out of the fill hose. Ask me how I know?
Embarassed
Tcash
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Ben Middleton
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PostPosted: Thu Jul 12, 2018 3:58 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Lol, I made sure to get it all out! I removed the pipe, checked for leaks and cleaned it all up. Only the lower grommet needed replacing.

I dismantled the Varga master cylinder. It was mostly clean inside. There was no visible cylinder paste inside, just brake fluid. I cleaned it out as best as I could with a combination of methylated spirits (denatured alcohol), a cloth and an air compressor. I tried my best to remove any contamination, but itís possible that thereís more in it now than there was before. I couldnít really tell because I used cylinder paste to rebuild it.

Bentley recommends silicone grease for a couple of areas but I didnít have any so I just used more cylinder paste.

I also dismantled, cleaned and rebuilt the pressure regulator again. I wanted to remove any residue from the brake cleaner I used before. I used the cylinder paste and brake fluid to rebuild it after cleaning with methylated spirits.

As I was refitting everything, I decided to check the clearance between the internal push rod in the servo and the master cylinder. There was no clearance. Quite the opposite. The depth of the tube on the master cylinder was 47mm, and the push rod was 54mm (approx). This means that the push rod had been opening the master cylinder at all times by 7mm.

The internal push rod is adjustable. I couldnít find any official resource that gave the necessary push rod clearance, but I found some discussions on The Samba that led me to giving it a 1mm clearance.

The bungs were also badly swollen. A comparison of the new vs old is shown below:

Image may have been reduced in size. Click image to view fullscreen.


I have now bled the brakes and things are initially seeming to be much better. I wonít get a chance to test it until I have fitted the new handbrake cables and adjusted the drum brakes. I will hopefully have reached the conclusion by tomorrow!
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Ben Middleton
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PostPosted: Fri Jul 13, 2018 7:41 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Well, Iíve bled the brakes but the pedal is now soft and going to the floor. Iím stumped.

Maybe thereís a vacuum leak somewhere, but thatís my only idea. Anyone else have some suggestions?
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Tcash
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PostPosted: Fri Jul 13, 2018 10:45 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Did you Bleed the master cylinder first?
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Ben Middleton
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PostPosted: Fri Jul 13, 2018 2:08 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

My master cylinder doesnít have a bleed nipple, or if it has, then I havenít noticed it lol. I bled the pressure regulator, then the front right, front left, rear right and rear left wheels.

The pedal is better now that Iíve adjusted the shoes, but it still feels kind of squishy. Iím going to replace the servo vacuum hose tomorrow just in case thereís a leak and Iíll fit the handbrake cables.

Fingers crossed!
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Ben Middleton
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PostPosted: Sat Jul 14, 2018 4:01 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Another frustrating day.

I tried to install and set the handbrake cables but it seemed like I had to use almost all the thread. It was obvious I needed to readjust the shoes again.

I slacked off the handbrake cables and tried to adjust the shoes again. My problem is that when I make them fully tight and back them off by 3 clicks, the shoes are still causing a lot of friction. I back them off until I canít hear them rubbing anymore, but that was probably too much. The second time, I backed them off about 7 clicks on each shoe until they were still rubbing but mostly free. The handbrake now works at about half of the thread on the cables.

After a test drive, the left rear drum is cool but the right one is very hot so I obviously need to adjust those shoes even lower.

I also havenít bought any air hose for the servo yet so I canít give feedback on how the brakes perform.

And the cherry on the cake, I dropped a massive car jack on my toe and it swelled up to quite a size.

Fun.
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Tcash
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PostPosted: Sat Jul 14, 2018 4:41 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Do you have a Bentley? https://www.amazon.com/Volkswagen-Station-Wagon-Service-Manual/dp/0837616352

Tighten adjuster until a slight drag and then back off, 3-4 turns.

Bleeding sequence
To bleed the Master, crack the brake lines as if they where bleeder valves.
Right front, Left front, Right rear, Left rear[/img]
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ToolBox
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PostPosted: Mon Jul 16, 2018 11:59 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

You need to adjust the brakes first, re-bleed, adjust, re-bleed, adjust, drive, check adjustment and once adjusted and bled properly do you install and adjust the park brake cables. No tension on park brake cables till the bled and adjust portion is finished.
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Ben Middleton
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PostPosted: Mon Jul 16, 2018 2:47 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Just curious, why do you need to keep bleeding? I have been through that process of bleeding it twice and adjusting it multiple times and I test drove it today.

Thankfully the rear brakes were cool when I returned, but the braking performance was dangerously bad. The pedal went completely to the floor and worked a bit better with some pumping. I know that means it is likely to have air in the system, but Iíve already bled it so many times. I donít understand how there can be any left in there. It may also be possible that Iíve adjusted the brakes shoes too low, but any higher and they rub on the drums.

Here is a video of me pumping the pedal before and after starting the engine. As you can see, my foot goes lower after starting the engine.

https://youtu.be/dn_b9wwFtI4

Any advice is greatly appreciated at this point!!
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Wildthings
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PostPosted: Mon Jul 16, 2018 3:02 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Some light rubbing is normal, just watch for excessive heating.
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Tcash
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PostPosted: Mon Jul 16, 2018 5:10 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Brakes adjusted and bled. There is no way your pedal should be that low.
Watch the videos and make sure you are bleeding the brakes right.

Please bleed the Master cylinder first.
https://youtu.be/0DcY5iQMtg4?t=387

Then bleed the brakes in this order. This is right out of the Factory VW Service manual.
Right front, Left front, Right rear, Left rear
https://youtu.be/qt3WQmv8SX0

Good luck
Tcash
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Ben Middleton
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PostPosted: Mon Jul 16, 2018 5:58 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Thatís honestly exactly what Iíve done. Iíve bled two or three times - in this order - master cylinder, rear brake pressure regulator, right front, left front, right rear, left rear.

Iím thinking the problem could be one of two things. Either I have adjusted the push rod wrong inside the servo or the brake drums are damaged to the point that I have to back them off too far to get them to stop dragging. However, I definitely canít move the drums with my hands when the pedal is fully engaged, which suggests that the rear brakes are functioning correctly - just too far down the pedal travel.

There definitely looks like thereís still air in the lines though. I just canít understand it.

As a side note, should the differential be moving the rear hubs when the gearbox is in neutral? Iíve noticed that the hubs only stop moving when the clutch is engaged.
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timvw7476
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PostPosted: Mon Jul 16, 2018 6:01 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Ben Middleton wrote:
My master cylinder doesnít have a bleed nipple, or if it has, then I havenít noticed it lol. I bled the pressure regulator, then the front right, front left, rear right and rear left wheels.

The pedal is better now that Iíve adjusted the shoes, but it still feels kind of squishy. Iím going to replace the servo vacuum hose tomorrow just in case thereís a leak and Iíll fit the handbrake cables.

Fingers crossed!

you gotta go old skool & get a 1/2 gallon plastic milk container & two quarts of
fluid & some gloves. Full Immersion Time. Also some brake cleaner too.
Clean it before immersion,pump it till bubbles disappear, bolt it in & attach lines, spray it down again. Bled.
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Wildthings
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PostPosted: Mon Jul 16, 2018 6:27 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

It is possible for the wheel cylinders to suck in air when you release the pedal. This is most likely happen with old cylinders and brakes that are way out of adjustment.

If you raise the corner you are bleeding it can help move any trapped air into the wheel cylinder so it can be purged, I have never found a need to do this on a VW though.
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Tcash
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PostPosted: Mon Jul 16, 2018 8:37 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Either I have adjusted the push rod wrong inside the servo or the brake drums are damaged to the point that I have to back them off too far to get them to stop dragging.

The drums are not causing air in the lines.
To rule out the pushrod. Loosen the master cylinder mounting nuts and bleed the system. If they bleed out, the pushrod is too long.

Good luck
Tcash
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guitarman63mm
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PostPosted: Mon Jul 16, 2018 8:59 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Are you sure you bled correctly? You're bleeding with the top bleeders on the front calipers, right? That is a massive amount of travel - assuming your M/C is now fine, either the rear wheel cylinders are sucking air, or there's something up with the way it's being bled.
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PostPosted: Mon Jul 16, 2018 9:26 pm    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

I can usually bleed the brakes on my late bay by just opening each bleeder in turn and letting the system gravity bleed. This may or may not work for you if there is a lot of air in the system. Yes on front calipers you need to bleed the upper bleed screw if there are two screws on each of your calipers.
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Ben Middleton
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PostPosted: Tue Jul 17, 2018 6:35 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

My front right caliper has two bleed nipples and the front left has one bleed nipple. I have been bleeding the top ones. I did also bleed the bottom one on the right caliper at some point though. Is there any disadvantage to bleeding the bottom right one?

Iím wondering whether it would be better to use a pressure bleeder. Although, would that allow the master cylinder to be bled?

Also, you can see in the video that I can pump the brakes up a little bit, suggesting there is air in the lines. However, once theyíre pumped up, does the brake pedal still appear to have too much travel?

I was under the impression that when the engine is turned on, the servo should raise the pedal slightly, but that doesnít appear to happen.
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guitarman63mm
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PostPosted: Tue Jul 17, 2018 7:37 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

Ben Middleton wrote:
My front right caliper has two bleed nipples and the front left has one bleed nipple. I have been bleeding the top ones. I did also bleed the bottom one on the right caliper at some point though. Is there any disadvantage to bleeding the bottom right one?

Iím wondering whether it would be better to use a pressure bleeder. Although, would that allow the master cylinder to be bled?

Also, you can see in the video that I can pump the brakes up a little bit, suggesting there is air in the lines. However, once theyíre pumped up, does the brake pedal still appear to have too much travel?

I was under the impression that when the engine is turned on, the servo should raise the pedal slightly, but that doesnít appear to happen.


The bottom bleeders are good to drain initially, as gunk accumulates at the bottom of the calipers - but because air rises, you can run all the fluid you want through the bottom, but it generally won't bleed completely (if at all).

When you start the motor, the pedal should drop slightly as the booster gets vacuum. It should not rise. Additionally, with the engine off and the booster emptied of vacuum, the only travel will be an inch of slack in the connecting rod/pedal assembly - it should be rock hard immediately after that. So, yes, you have way too much travel.

A pressure bleeder is not necessary to bleed these cars, although some people use them. I use speed bleeders with a check valve, because it's easy to accidentally let air back in the lines with an assistant. At this point, I think you should crack the lines, put some hoses on each one, and let it gravity bleed while you have a beer and monitor the top reservoir. You can then do one final bleed per the Bentley if it's still soft.

You should buy a hard copy of the Bentley and follow it verbatim.

Review the bleeding steps and see if there's something missing.
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PostPosted: Tue Jul 17, 2018 7:38 am    Post subject: Re: Rear Drum Brakes Locking On (1972 Camper) Reply with quote

The bottom screw could be used to better flush any crappy old fluid out but can not get the air out of the top of the caliper, so will not work for bleeding the brakes.

What does the pedal feel like when you have the parking brake on? Does it pump up easier? Try adjusting the rear brakes up tight and see if that improves things.
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