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drum brake experts?

Old 09-10-2019, 05:27 AM
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Default drum brake experts?

figure if anyone can add suggestions it will be the THT experts.

1973 VW Beetle, put all new front brakes in. wheel cylinders, lines etc. bleeding brakes, I can get the pressure firm at the pedal and hold it forever. if I let off the pedal and then reapply pressure, no "feel" at all. pedal goes right to the floor.
we have bled all 4 wheels many times and cannot get the pressure to stay in the brakes. no fluid leakage at all.

I am thinking master cylinder but thought I would get other opinions.
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Old 09-10-2019, 05:30 AM
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Bleed the master...rear line first
Did the master go dry during the initial bleed??
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Old 09-10-2019, 05:41 AM
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Originally Posted by Lprizman View Post
Bleed the master...rear line first
Did the master go dry during the initial bleed??

hmm may try that.

no never dry.
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Old 09-10-2019, 05:55 AM
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Keep looking either a leak , or master cylinder ...
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Old 09-10-2019, 06:00 AM
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Are the shoes fully adjusted so there is a slight drag when you rotate the wheels?? The springs will pull the pistons back in, unlike a disk brake. If you had to pump the pedal to push the shoes out to make contact when you bled the brakes, the springs will pull them back in when you're done. This would require you to pump several times to get them back out to the drum and make the pedal firm again.
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Old 09-10-2019, 06:04 AM
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Shoe adjustment issue.
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Old 09-10-2019, 06:10 AM
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My thoughts are if the shoes were adjusted properly after install, the seals in master cylinder leak by when pushed slowly.
quick/ sudden pushing should flare the cups seals to seal better.
new master should take care of it,
not a fan of rebuilding those old units myself,
usually to much cylinder damage from moisture in the fluid for too many years
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Old 09-10-2019, 06:14 AM
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Rule #1 doing drum brakes, do one side at a time so you can look at the opposite side to see how it all goes back together.
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Old 09-10-2019, 06:22 AM
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Originally Posted by PF-88 View Post
Rule #1 doing drum brakes, do one side at a time so you can look at the opposite side to see how it all goes back together.
Says a man that has learned from experience!
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Old 09-10-2019, 06:29 AM
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Originally Posted by muskamoot View Post
Shoe adjustment issue.
i think this is right.

But, I had my master go out last time I changed my disk cylinders out. Pretty common in an old unit that is used to be running on a certain stroke. When you go to bleed you are pushing the piston past the old stroke distance and it gets caught in the corrosion further down the master cylinder walls. It gets hung up and doesn’t return to the starting position. Then you get nothing on the petal when you try to press the brake again.

My symptoms. Replaced the cylinders. While bleeding the system the first press of the brake would have good pressure and bleed as expected but if I went to try again it would have nothing. Then if I let it sit for a while it would work. Then the second try nothing. Replaced the master and it worked flawlessly.
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Old 09-10-2019, 06:47 AM
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pretty confident I have the shoes properly adjusted. I may take it apart and look everything over again just to be sure.


Originally Posted by mwgoldman View Post
My symptoms. Replaced the cylinders. While bleeding the system the first press of the brake would have good pressure and bleed as expected but if I went to try again it would have nothing. Then if I let it sit for a while it would work. Then the second try nothing. Replaced the master and it worked flawlessly.
we had something very similar to that as well.

just looked up bleeding and replacing master cylinder on it....oh crap, this will not be a fun job. LOL
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Old 09-10-2019, 06:58 AM
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Confirm shoe adjustment then replace master.
pretty easy on a beetle, just shoot it with pb blaster the day before.
Use the proper line wrench, the flare fitting like to round off.

the forward and rearward shoe material on old beetles are two different sizes. Make sure you orient them properly or you will encounter weak braking power.
The pedal will get hard but the car won’t stop well.
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Old 09-10-2019, 07:18 AM
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Try pressure "bleeding". Push fluid UP from the wheel to master.
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Old 09-10-2019, 01:18 PM
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Originally Posted by PeteH View Post
Confirm shoe adjustment then replace master.
pretty easy on a beetle, just shoot it with pb blaster the day before.
Use the proper line wrench, the flare fitting like to round off.

the forward and rearward shoe material on old beetles are two different sizes. Make sure you orient them properly or you will encounter weak braking power.
The pedal will get hard but the car won’t stop well.
Primary (closest to the front of the vehicle ) (shorter lining) and secondary shoe.
The lining is usually thicker on the front one also
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Old 09-10-2019, 01:43 PM
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Originally Posted by Thalasso View Post
Primary (closest to the front of the vehicle ) (shorter lining) and secondary shoe.
The lining is usually thicker on the front one also
Thanks, it’s been a very long time... those were the days.
Only bugs where I am now are superbeetles, not sure I want to restore one of them.
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Old 09-10-2019, 01:50 PM
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Originally Posted by PeteH View Post

Thanks, it’s been a very long time... those were the days.
Only bugs where I am now are superbeetles, not sure I want to restore one of them.

Refuse to work on any german/ European garbage.
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Old 09-10-2019, 02:15 PM
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Originally Posted by Thalasso View Post

Refuse to work on any german/ European garbage.
haha currently own a mini BMW and a Passat Variant! Guess I am screwed 🤣🤣
At least they are both diesel.
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Old 09-10-2019, 02:34 PM
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I vote for a bad master cylinder. Bleed the new one before installing it.
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Old 09-10-2019, 03:24 PM
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Originally Posted by avenger79 View Post
pretty confident I have the shoes properly adjusted. I may take it apart and look everything over again just to be sure.




we had something very similar to that as well.

just looked up bleeding and replacing master cylinder on it....oh crap, this will not be a fun job. LOL
Well,did you turn the adjusters out from the backside with the drum on until they dragged locked and then back the adjuster off?
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Old 09-10-2019, 03:29 PM
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Originally Posted by PeteH View Post

haha currently own a mini BMW and a Passat Variant! Guess I am screwed 🤣🤣
At least they are both diesel.


Good for you is all i can say.
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