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Leaking brake light switch on 1970 VW Bug master cylinder
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DocErickson
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PostPosted: Tue Jun 08, 2010 6:36 pm    Post subject: Leaking brake light switch on 1970 VW Bug master cylinder Reply with quote

So, I just installed a new master cylinder (Brazilian, not German) and did all the things you are supposed to do (bench bled, adjusted brakes, remove drums to check slave cylinders...etc.) and the front brake light switch is leaking. I cranked down on it as hard as I could and it's still leaking. I tried replacing it with the old one and it still leaks. That leads me to one of two conclusions. The MC is trash or the I misadjusted the push rod and it's going down too far, but I'm pretty sure I adjusted it right. Should I replace the master cylinder again or is it the push rod adjustment that I messed up?

Thanks for your help.
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dakdak
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PostPosted: Tue Jun 08, 2010 6:43 pm    Post subject: Re: Leaking brake light switch on 1970 VW Bug master cylinde Reply with quote

DocErickson wrote:
So, I just installed a new master cylinder (Brazilian, not German) and did all the things you are supposed to do (bench bled, adjusted brakes, remove drums to check slave cylinders...etc.) and the front brake light switch is leaking. I cranked down on it as hard as I could and it's still leaking. I tried replacing it with the old one and it still leaks. That leads me to one of two conclusions. The MC is trash or the I misadjusted the push rod and it's going down too far, but I'm pretty sure I adjusted it right. Should I replace the master cylinder again or is it the push rod adjustment that I messed up?

Thanks for your help.


When you say you "cranked down" as hard as you could, it is possible you may have craked the master cylinder at the threads. Check the master cylinder around the brake light switch threads for any cracking. If you're satisfied it's not cracked, you may try using the white teflon thread tape on the switch threads and see if it still leaks. This may draw some criticism, but if it works, it works.
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DocErickson
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PostPosted: Tue Jun 08, 2010 6:47 pm    Post subject: Reply with quote

I had it pretty snug to begin with, saw that it was leaking when my assistant was pushing on the brakes, so I gave it another quarter turn, and I'm no Hercules, so I'm pretty sure I didn't crank it too hard. I'll try the dope tape method.
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69 Jim
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PostPosted: Tue Jun 08, 2010 7:44 pm    Post subject: Reply with quote

Not a good idea to trust your life on a garbage Brazil made master.
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DocErickson
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PostPosted: Wed Jun 09, 2010 5:17 pm    Post subject: Reply with quote

After all was said and done, I replaced the brake light switch with genuine German switches with high temp thread sealer, and it's holding up as of right now. Now I have to wait for my assistant to help me bleed my brakes.
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johneliot
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PostPosted: Wed Jun 09, 2010 11:30 pm    Post subject: Reply with quote

I had exactly the same problem with my 69. I decided to go cheaper with the MC (i was a Varga I believe). No amount to tightening would stop th leak. I decided to eat the $25 and buy a German one and it never leaked again. You should not have to use any type of sealer on the switches. Brake fluid eats paint in no time, I can't imagine what it would do to teflon tape.
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69 Jim
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PostPosted: Thu Jun 10, 2010 12:06 am    Post subject: Reply with quote

My switches came with brown loctite on them.
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Cusser
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PostPosted: Thu Jun 10, 2010 6:28 am    Post subject: Reply with quote

johneliot wrote:
You should not have to use any type of sealer on the switches.


Agree.

johneliot wrote:
Brake fluid eats paint in no time, I can't imagine what it would do to teflon tape.


Teflon (polytetrafluoroethane or PTFE) won't dissolve in brake fluid, or most anything.
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bogrady
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PostPosted: Mon Dec 13, 2010 10:30 am    Post subject: Reply with quote

Where did you purchase your part from? I am having the same problem and need to know the best/cheapest place to get it.

Thanks!
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JonF
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PostPosted: Mon Dec 13, 2010 11:35 am    Post subject: Reply with quote

i had a prob over the summer with brake light switches also! there was a bad batch of switches made and i had to replace the switches 3 times before i got 2 good switches.

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marcodelat
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PostPosted: Mon Dec 13, 2010 12:44 pm    Post subject: Reply with quote

DocErickson wrote:
... Now I have to wait for my assistant to help me bleed my brakes.

While you are waiting... let gravity be "your assistant"... in other words try gravity bleeding - do a search here or on the net.
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velvetguru
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PostPosted: Thu Dec 16, 2010 10:12 pm    Post subject: Reply with quote

Why not just rebuild your original German made master cylinder. A kit is inexpensive and easy to install, it's just a few rubber parts and a spring. You have the advantage of keeping the car original and you don't have to deal with all these new 'just as good as the original' junk parts being made today. Just my two cents.

Joe
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rtaylor
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PostPosted: Thu Jan 06, 2011 4:18 pm    Post subject: Reply with quote

if anyones still checking this post, it has been a while since it was posted, butt im having the same problem with my brake switches. ive gone through litterally 8. autozone has replaced them everything since they have a warranty. buttt im gettin tired of buying brake fluid and having to bleed my brakes. soo any idea of a better palce i can go? i just ordered some from napa.....but if they ont work i need a back up plan
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