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Old 04-29-2014, 12:22 PM   #1
cmye
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Karmann Ghia brake pedal is not firm

Brake pedal is not tight.
I have read and viewed the many Web sites that provide instructions about overhauling the brakes on my 1965 Karmann Ghia. This car has a single cylinder master cylinder and drum brakes in the front and rear. My work on the brakes started because the car had been garage parked for some years, the lumens of the rubber hoses had swollen shut, a couple of the brake shoes were thin, and the rubber hose from the brake fluid reservoir was leaking. I decided to do a complete overhaul.
1. I installed a new German master cylinder (I bench bled it before installation). This was after installing a new Varga and being unable to get a firm pedal. I installed a new rubber hose from the reservoir to the metal line that connects to the (new) bung on the master cylinder. I installed new rubber brake hoses, new wheel cylinders, new shoes, and new shoe-mounting hardware (springs, etc.). Before reinstalling the drums, I checked to be sure that pressing the pedal causes the wheel cylinder pistons to move at all eight positions and causes all eight shoes to move. It all works. I reinstalled the drums. All fitting nuts are tight, and there are no leaks anywhere.
2. The brake system has been bled (several times), using a hand-held vacuum pump, following these steps: Remove the vented cap from the brake fluid reservoir; make sure the reservoir is full; starting at the right rear wheel; attach a box (hex) wrench to the bleeder valve; attach the vacuum pump (VP) (with transparent collection bottle) with a transparent hose to the bleeder valve; have an assistant pump the pedal about 4 times and hold it down; pump the VP to about 20 psi; open the bleeder valve; watch the brake fluid flow, looking for bubbles. Repeat the VP pumping until there are no bubbles. Close the bleeder valve. Have the assistant release the pedal. Have the assistant pump the pedal 4 times and hold it down. Open the bleeder valve. (When we do this, the fluid that flows has no bubbles.) Close the bleeder valve. Have the assistant release the pedal. Replenish the fluid in the reservoir. At each wheel, this collects about 3 fluidounces of brake fluid in the bleeder container.
3. Do the same at the left rear wheel. Then do the same at the right front wheel. Then do the same at the left front wheel. Replace the reservoir cap.
4. I adjusted the star “wheels” to set the shoes and adjusted the emergency brake tension. After each one-notch movement of the star wheel and after each quarter turn of the emergency brake adjustment nut, the brake pedal was pressed a couple of times to make certain that everything in the drums was “centering” correctly.
5. When the car is up on jack stands and each wheel is rotated, pressing the brake pedal stops the wheel rotation. The emergency brake works. But the pedal is not tight, and during a short test drive in an isolated neighborhood, the brake pedal just does not stop the car reliably. The emergency brake works fine.
6. Some more details: The “play” in the pedal before the plunger rod can be felt encountering the piston in the master cylinder seems correct. The adjustment nut on the plunger rod has not been moved. The pedal stop plate has not been moved.
7. What should I try next? Does anyone have sufficient experience in using an electric vacuum pump to say whether that might make any difference? (Maybe there is still air somewhere in the hydraulic pathway that my hand-held vacuum pump is just not strong enough to remove?) The price to buy one of these seldom-used machines seems high, although I might be able to rent or borrow one. I have even considered going to an automobile junk yard and removing an electric vacuum pump (if I could find one) to fashion a DIY unit. The central question, though, is whether using a stronger vacuum (stronger than my hand-held) is likely to be helpful. Again … does anyone have experience with this?
Many thanks for any help.
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Old 06-17-2014, 12:38 PM   #2
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Re: Karmann Ghia brake pedal is not firm

Here is the latest on my efforts to get a firm brake pedal in my 1965 Karmann Ghia.
A. First, a quick review: I replaced the master cylinder, all rubber hoses, all wheel cylinders, and all shoes and shoe-mounting hardware. After brake adjustments via the star wheels, I could not get the pedal to be firm. The car was unsafe to drive.
B. Based on someone’s advice, I adjusted the shoes all the way out against the drums. (In that position, the pedal was very tight - - no surprise.) Then I bled the brakes. Then I backed the shoes away from the drums (two star-wheel clicks beyond the last discernible dragging).
C. The result: A firmer pedal than in A, and the car can be driven safely.
D. But why not an even firmer pedal? What I think may be going on is that the new shoes may not have a radius that perfectly matches the radius of the drums. The shoe surfaces also may not be perfectly in the plane of the drum surfaces. (One clue to this is the fact that at least one of the old shoes that I removed was worn thinner on one edge than the other. It is possible that that drum may be flared a bit.) So I am thinking that, after some gentle driving and braking and some repeated re-adjustments to the star wheels, the new shoes will become better “seated” to conform to the drums and that the pedal may become firmer as that occurs. Anyway, that is the hope.

If something else develops, I’ll post something.

If I had all this to do over, I would convert the system to a dual master cylinder. As for the much bigger conversion to disc brakes, it would be nice but very expensive and maybe even beyond my DIY capabilities. Finding anyone in Richmond VA who could do it for me may not be possible. Air cooled VWs are just too rare here for most repair shops to have anyone who has even worked on one.
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Old 06-17-2014, 08:01 PM   #3
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Re: Karmann Ghia brake pedal is not firm

What you needed to do was to lay the brake shoes in the drums before you assembled them to see that you don't have full contact with the drums. Measure the drums and see that they're worn beyond their limits. The drums may also have bad taper due to old, weak brake shoe springs and retaining hardeware. So remove the drums and inspect the rub marks on the shoes. If they're not making complete and concentric contact with the drums replace them. Back in the day I could have drums turned and shoes arced to the drums but I doubt anyone does that anymore.
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Old 06-18-2014, 08:43 AM   #4
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Re: Karmann Ghia brake pedal is not firm

Thanks, DeltaP. All good ideas. If I replace the drums, is there any assurance that the new drums and new shoes will have the same radius (same curvature)?

I'll post progress notes, when I can get around to working on it more.
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Old 06-18-2014, 08:37 PM   #5
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Re: Karmann Ghia brake pedal is not firm

They should if they're quality parts. But you can still check them using the fore mentioned method. Just lightly sand the old rub marks off the new linings and mount the new drums,adjust brakes then turn the drums,remove the drums and inspect contact patch. HTH
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Old 06-19-2014, 08:12 AM   #6
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Re: Karmann Ghia brake pedal is not firm

OK. Thanks.

It looks as if drum-brake technology is becoming a thing of the past. I called my usual mechanic shop to ask whether they turn drums. They said not anymore. A second shop said, with some reluctance, that they COULD do it but then started talking about what a long and complicated process it would be. (???) I could tell they really did not want to do it. The person who answered the phone at a third shop wasn't sure whether they could work on an air-cooled VW. He did not know what a Karmann Ghia was. After I explained, he said they seldom work on what he called "antique beetles."

If I get this set of brakes going well enough, it looks as if the NEXT brake job after that will likely be a disc conversion (if I can find someone to do it right).
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Old 08-10-2014, 11:13 AM   #7
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Re: Karmann Ghia brake pedal is not firm

Problem solved. The drums were so worn that the inside diameter exceeded the distance that the wheel cylinders were able to reach with sufficient tightness. After I replaced the drums (along with new bearings for the front), the pedal is now good.
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Old 08-10-2014, 12:51 PM   #8
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Re: Karmann Ghia brake pedal is not firm

Thanks for letting us know.
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