Help - Brake Distribution Block Leaks at Switch Port

65-Fstbk

15 Year Member
May 20, 2007
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Vancouver, B.C. Canada
Hey All,

I am having issues with the brake distribution block leaking at the switch when bleeding the brakes.
I did a front drum to disc conversion, switched to a dual bowl master and did the plumbing.

I started with a Circa 1970 original distribution block - leaked at switch port when bleeding
I heard that placing a pin-stopper in the switch port prevents the piston from moving when bleeding so I tried that
Still leaked at switch port (fluid should not get to this area)
So I bought a rebuild kit and rebuilt the block - still leaked at switch port
Took it apart, checked everything and remounted it 3 times and 3 times it still leaked at switch port
I also confirmed with the company that sells the rebuild kit that my gaskets etc were all in the correct orientation
Finally gave up on that and ordered a new distribution block - leaked at switch port (with pin-stopper in)
Company I bought it from sent me a new one - installed that - leaked at switch port

There has got to be a solution for this. I am now thinking of scrapping the block and going with an adjustable proportioning valve that takes both lines from the Master but allows you to dial back pressure to the rear drums once the system is bled. Has that worked for anyone?

Other solutions?

Thanks Guys
 
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My 2 cents

Leaks at the plastic right?
70 P-block

Lower Right corner picture switch slides to the fitting and stops.
Wrong fitting then switch slides to far and leaks


brake-pressure-differential-switch.jpg
 
maybe post a picture of it
I've got a short video clip (from my phone) but this website doesn't accept the file extension. I have uploaded to YouTube and placed a link here.

View: https://youtu.be/DoDrYe_kSls

Hopefully this works.
Note I have tried this many times, rebuilt the block, new blocks, with switch in place with the green pin stop in place. They ALL leak.
 
You got fluid coming out all 4 bleeders?
Just a guess, but for so many attempts to fail, there must be rubbish/ rust in the old lines thats damaging the o rings?
But with the pin stopper you would think the o-rings are not rubbing yet...

If they sent a new one without getting old one back makes you think they have had this problem before.
Just maybe you got a damaged original followed by a couple pf crappy replacements?

This is your second thread on this right?
Other than that I aint got nothing.
 
You got fluid coming out all 4 bleeders?
Just a guess, but for so many attempts to fail, there must be rubbish/ rust in the old lines thats damaging the o rings?
But with the pin stopper you would think the o-rings are not rubbing yet...

If they sent a new one without getting old one back makes you think they have had this problem before.
Just maybe you got a damaged original followed by a couple pf crappy replacements?

This is your second thread on this right?
Other than that I aint got nothing.
All the lines are new.
It has me perplexed and it seems this problem is not that unusual.
I have tried and original 1970 era block and that leaked,
I rebuilt it 3 times and had the rebuild guy confirm my seal placement was correct - leaked 3x
I bought a new block - leaked
I installed a replacement new block - leaked
If this new block leaks you may see the car on Craigslist. LOL
 
Hmmmm, I haven't checked that. Wouldn't think anything surprising b/c it's just a manual disc/drum setup with a new dual bowl master.

I ask because its remotely possible that for some reason the pressure is higher that what the o-rings are able to stop. I couldn't say why that would be...but its the only thing I can really think of...unless the o-rings are simply too small or you have had a run of bad brake switch blocks
 
Over the weekend I purchased an adjustable proportioning valve that accepts both front and rear lines. I had to do some replumbing of the lines and fab a homemade bracket but got it in. So far no leaks.

BTW - If anyone needs to run double flares on brake lines I would highly recommend the Titan tool. I have no financial incentive, no freebies etc but the tool worked way better than those typical flare kits. If anyone wants me to post a pic of it let me know. Nice to use a tool that works nicely.
 
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