Right rear brake shoes lock up after one pump of the brakes

[djdh68dlux]

Hey all, having an issue on my 1968 bus. I was driving home a couple of weeks ago and I could feel some brake drag. No problem, figured I just needed to adjust the shoes as I had recenlty put new ones on. It got worse and worse as I drove home. By the time I got home, it was dragging so badly that it was like driving with the E-brake on. Passenger side rear wheel was hot and smoking. Let it sit for a few days until I had time to look into it. Got the drum off, decided to replace the Brazilian wheel cylinders with FTE German ones, readjust the shoes, bleed and be done. Problem is that after one pump of the pedal, the same passenger side rear wheel brake shoes go all the way to the drum and do not release, like the brake fluid pressure can't travel back through the line and into the reservoir. Now, I did a search here on the forums and the consensus seemed to be that the brake hose on that wheel must have gone bad on the inside and may be acting as a check valve, not allowing the fluid to travel back through the line. No problem, cheap fix, replace the hose, right? Only that didn't fix the problem! So search some more, and read up on adjusting the Master Cylinder push rod. Seems simple enough. I remove the pedal cover/skid plate, check the push rod and from what I can tell, it doesn't seem horribly out of adjustment. Bentley calls for 1mm of play between the rod and master cylinder piston. While it seems like it might be slightly more than 1mm, I'm pretty positive that it's no way more than 2mm at the most. The way I understand it, the piston needs to come all the way back to not block the compensating port so the fluid can return to the reservoir, correct? Wouldn't the push rod have to be adjusted too long for that to happen? How could that happen if I am a half a mmm to 1 mm shorter than recommended? My next thing to try was going to be to back off the push rod and then readjust it to the 1 mm spec. If that doesn't work, what's next? Remove the Master, clean, reinstall? Master isn't super old, but not new anymore either (5-7 years old). I'm super stumped, so I appreciate all suggestions/ideas at this point. I've never had this problem in the 25+ years I've owned this bus.
_________________
1968 Deluxe "Clipper L" Type 2

Looking for a VW club in Southern California? Check out Inland Valley Volkswagens: www.ivvw.org

[vwwestyman]

Hopefully others will have other ideas too, but I think the idea that maybe something is wonky in the master cylinder makes sense. Perhaps some crud got in there and found it's way into the port for the rear brakes or something to that effect.

OR

Perhaps a bit of crud found it's way into the brake line when you replaced the cylinder, and has finally made it's way to some point in the lines between the front and back that it is acting as a check valve.

So maybe you could unhook the line from the back of the wheel cylinder and just run a bunch of fluid through the lines and see if you get anything out?
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[busdaddy]

If it was the master cylinder more than just one brake would be acting up, I'm going with the crud in a line (maybe even one of the hard lines) playing check valve as well.
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[djdh68dlux]

[SGKent]

Check the shoe return springs. If that isn't it, remove the hose from the wheel cylinder and from the Tee, and blow air thru it. See if it is restricted.

A single master would affect all 4 brakes, a dual master would affect the front or rear. The problem is downstream of the rear tee. That means either a hose, line, or return spring. This assumes it worked right at one time and that it hasn't been assembled wrong.

ALSO make sure that the hand brake cable is not sticking.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[djdh68dlux]

[Wildthings]

What happens when you open that bleeder on that wheel after you have pumped the brakes up? Do you get a slight squirt? Can you hear the brakes returning? What happens when you open the bleeder on the opposite side of the car?

[aeromech]

Are your star adjuster locks in place? Could it be that your shoes are getting tight from movement of the star adjusters?
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[djdh68dlux]

[aeromech]

Pull the drum and take some pictures
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[SGKent]

the line or hose, wheel cylinder where the line comes out is plugged up. The squirt and retraction is proof of that.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[djdh68dlux]

Thanks all for the suggestions. Gonna dig into it tomorrow morning before the temps crawl up to triple digits and I'll see what I can find and will update you all here.
_________________
1968 Deluxe "Clipper L" Type 2

Looking for a VW club in Southern California? Check out Inland Valley Volkswagens: www.ivvw.org

[SGKent]

[Starbucket]

I would remove the rubber hose to that wheel as the symptoms are the same as an older hose with swollen inner rubber, fluid goes in but return springs are not strong e`nuff to return it, that said did you replace the brake springs?

[djdh68dlux]

[SGKent]

[Starbucket]

How did you adjust the brakes when you rebuilt them, adjust one shoe 4 clks then the other shoe 4 clks until you got contact? if not you may have shoved one piston off center blocking the inlet.

[orwell84]

I did drum brakes for the first time ever this summer. It was harder than I thought. I adjusted them with the wheels off and checked as I adjusted by pulling the drum on and off and checking progress. It took me awhile to get it right. Then pulling the unadjusted parking brake lever caused something to rub and make noise. It went away after I adjusted the slack out of the e brake cables.

[Starbucket]

[busdaddy]