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Seized brakes FAQ
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Joined: July 12, 2003
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jakemcarroll@excite.com is offline 

PostPosted: Sat Jul 12, 2003 1:29 pm    Post subject: Seized brakes FAQ Reply with quote

I am a newbie on the bus scene, my father and I recently purchased a 75 bus and are cureently restoring, we had noticed a major lack of power, we have realized that both front brakes (which are disc brakes) are fully engaged at all times. looking for advice, thanks.
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ratwell
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Joined: April 26, 2003
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Location: Victoria, BC
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PostPosted: Sat Jul 12, 2003 4:41 pm    Post subject: seized brakes Reply with quote

An overhaul of the brake system sounds in order. I've written a lot here because once you get started and make one change you may not be able to stop because all of the parts are interconnected and the problem will just move someplace else.

First, the REAR brakes:

- First back off the parking brake adjustment underneath the cab (almost underneath) all the way on both wheels.

- Loosen the adjustment screws on the rear and remove the drums. Turning the stars clockwise engages the shoe so go the other way. If you point your thumb parallel to the screw from the outside of the wheel then clockwise is the direction your fingers curl.

- The drum may not want to come off because it may be rusted to the hub in the center. Look at a picture of a drum removed and you can see where it will seize: th inner circle. Use a penetrating oil, let it setup and give the drum a few whacks with a deadblow hammer.

- Inspect the drums looking for out of round. You may want to get them turned. Second, What condition are the shoes in? New shoes have about 5mm of brake material. Do they need replacing? Is either rear wheel cylinder leaking and in need of replacement? Everything is easy up to this point.

- Do the flex lines going from the brake lines to the wheel cylinder have the original x/77 or x/78 DOT tag on them? If so they are original then the rubber is beyond end of life and they need to be replaced because they won't let to brakes release. You'll need an 11mm wrench and a crescent wrench or buy two 11mm flare nut wrenches for brake lines.

- There is some hardware in the brake drum like springs and such that need periodic replacement. Might as well do it all while you are in there.

- Before reassembly of the rears you want to use anti-seize compound in the barrels and on the threads of the adjustment screws so you won't have difficulty adjusting them in future. They do seize without it.

- Check the parking brake cable. Do you need a new one? They typically last a very long time.

- Adjust the rear brakes using the adjustment screws. Turn them each a little under the drum drags on the shoes and back off slightly. You always want a little drag so the brakes engage right away. I should point out that connecting the rear brakes is a proportioning valve. It's bullet proof so you don't have to worry about it.

The FRONT brakes:

- You need to make a similar inspection to both of the flex lines up front.

- Remove the spring plate and the two pins. If they are rusty you should replace them with new hardware.

- Remove the pads. Are they worn down? How about the rotor is it warped or so severly rusted it will chew new pads to pieces? New rotors aren't expensive.

- Simply putting on new pads may cause the brakes to rub if the hydraulic part of the system has aged. What little clearance there was before will be eliminated when new (thicker) pads are put on and you'll get squealing.

- Inspect the dust boots on the inside of the calipers. Are they torn? If so you'll need a seal kit because a torn boot will let crap inside and contaminate the seal. The seal keeps the fluid out but also helps to retract the piston in the caliper. You do not need to split the caliper to replace the o-rings to complete the seal replacement. See bentley for instructions.

- Next, are the two backing plates in good condition. You will probably be corroded and have lost their nice cadmium plating but you can sand them down smooth. What about the tabs in the backing plates? Do they engage the tabs in the pistons? If they are flat the pistons may have rotated and this will cause vibration when braking. Pop the tabs out enough to engauge the pistons.

- There are pliers from ATE designed to rotate the piston in place but I can't afford them. Be careful rotating the piston because the piston metal is porous and it can chip. Hopefully you'll need new seals and you can orient the piston at this time. Use brake fluid for lubricating everything during assembly. VW says use brake paste but it's not readily available anymore even from over the counter at the VW dealer.

- Put it all back together and then check the rubber lines from the brake fluid container to the container on the master cylinder. Check the MC. Are there boots covering the two switches. Are the containers cracked. Adjust the MC is a last resort as it the other parts wear out first.

- You can now replace all fluid and bleed system. Bleed from longest lines to shortest (pass rear, driver rear, pass front, driver front). On the front brakes bleed from the bottom screw until new brake fluid comes out then bleed from the top screw to remove any trapped air. Have someone stomp on the brakes 5-6 times and you may find the rears do not drag anymore. If so, then re-adjust them until they do.

- Use Castrol LMA brake fluid. buy 1 32 oz bottle and the smaller 12-16 oz. I would say buy two 32 oz. bottles but what you don't need you'll just have to throw away once you open the bottle.

- Last step is to adjust the parking brake. It helps to have a second person engage the e-brake while you try to rotate the tires. Go for 8 clicks of the parking brake because the brakes will wear out and you'll have to pull the lever more until the next adjustment. Two few clicks and you may be premature wear.
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jah_B
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PostPosted: Fri Nov 07, 2008 8:51 am    Post subject: Reply with quote

So, if the brakes operate fine, new pads, and look otherwise in decent condition, would you even bother to clean a coat of rust off the rotors before rolling off down the road?

What would you do, pull the rotors and have them lightly turned, just wire wheel 'em, hand wirebrush and a can of brake cleaner, or just let the pads and brake pedal do it for you in the first couple of miles? Mind you, this is AZ rust, NOT New Hampshire rust....

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I know it's a lame, small potatoes question... but this is my baby..and I want to do the right thing when she finally comes down off the jackstands...
_________________
1984 CABRIOLET 6spd, quaife diff, Neuspeed springs, sway bars, tie bar, short shift kit, bilstein shocks, 16X7 RSE 3pc wheels, BFG TA 205 40s

1972 tintop P30 CAMPMOBILE: M/T, 1.7L, dual kadrons, 019 diz. Sunny the S'kool Bus


You gotta know what you don't know. That's the key to wisdom. man.
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keifernet
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PostPosted: Fri Nov 07, 2008 9:00 am    Post subject: Reply with quote

John, I would take the caliper off ( to the side, leave line attatched, no fluid loss) and use 36 or 40 grit sand paper ( by hand and or on a sanding block) and "dress" the rotor surface to get that off and leave a nice scratched up de glazed surface for the pads to seat into again when you get her rolling.

You might want to see if the rear drums need to be deglazed too..
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jah_B
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PostPosted: Fri Nov 07, 2008 9:03 am    Post subject: Reply with quote

Cool. Thanks. That'll keep me busy for an hour or so... Cool
_________________
1984 CABRIOLET 6spd, quaife diff, Neuspeed springs, sway bars, tie bar, short shift kit, bilstein shocks, 16X7 RSE 3pc wheels, BFG TA 205 40s

1972 tintop P30 CAMPMOBILE: M/T, 1.7L, dual kadrons, 019 diz. Sunny the S'kool Bus


You gotta know what you don't know. That's the key to wisdom. man.
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