Brake bleeding

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blab
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Brake bleeding

Post by blab » Sun Aug 19, 2018 5:22 pm

Hi,

I replaced the master and wheel cylinders on my 64. I tried to bench bleed the master but had never ending bubbles:

Image

So it must have pulled air somewhere, either through the piston opening, through the brake light switch, through the connectors or through the connector block.

There is a very small leak at the master / connector block junction. So I think that's where the air comes in. When I screwed the block in, it stopped at the opposite side. Which meant the rear brake line wouldn't fit. It needed some force for the half turn more.

The question is what to do now. I'm puzzled why it would leak. Is this fixable? Do I need a new brass block? Put some sealer on the thread?

Thanks,
Stefan
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Joe Johnston
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Re: Brake bleeding

Post by Joe Johnston » Sun Aug 19, 2018 6:54 pm

The first thing I would do is to remove the brass block and just run one tube back into the reservoir and start over. You have increased the potential for leaks immensely.
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blab
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Re: Brake bleeding

Post by blab » Mon Aug 20, 2018 3:08 am

That should solve the bubbling during bench bleed. I'd still have the connector block leak though, probably.
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sseebart
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Re: Brake bleeding

Post by sseebart » Mon Aug 20, 2018 11:36 am

Don't discount the possibility that the new unit is bad. I've purchased more than one (especially the reconditioned variety) that were doa.

~Steve

Terry64HT
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Re: Brake bleeding

Post by Terry64HT » Mon Aug 20, 2018 12:27 pm

Bench bleeding these old rebuilt (several times?) masters can be a bit of a trick. The instructions that come with it usually tell you not to push the piston more than about 3/4 to 1 inch so not to damage the seals. If you still get bubbles after the brass block is removed, you need to exchange the master.
Terry
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blab
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Re: Brake bleeding

Post by blab » Mon Aug 20, 2018 1:08 pm

I'll test without the brass block.

The master should be new: https://www.rockauto.com/de/moreinfo.ph ... 281&jsn=10

Did it happen do anyone that the rear pipe connection turned out to be on the wrong side? What did you do? I'm wondering if I broke something when giving it that half turn more.
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paulr
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Re: Brake bleeding

Post by paulr » Mon Aug 20, 2018 1:21 pm

blab wrote:
Mon Aug 20, 2018 1:08 pm
Did it happen do anyone that the rear pipe connection turned out to be on the wrong side? What did you do? I'm wondering if I broke something when giving it that half turn more.
I don't use my '64 brass block anymore due to a modded system. It never leaked when I did use it, but it sure looks like it's cracked. Guys always say to crank down hard to get that seal. With a flair it either seats or isn't seated yet. I always think it's easier to bend the tube than ruin threads. Those blocks are not easily available as far as I know. You might consider fabbing something with new fittings. Wish I had better help.
Paul
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blab
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Re: Brake bleeding

Post by blab » Mon Aug 20, 2018 2:00 pm

The blocks are available from the parts houses. I think I'll get a new one just in case.
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RAVEN
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Re: Brake bleeding

Post by RAVEN » Mon Aug 20, 2018 2:25 pm

Brass blocks are readily available through TBird suppliers. Take note they are not a flair fitting but a Pipe thread taper fitting. You tighten till the threads mesh and seal. Do to fact that the threads are tapered, over tightening with brass threads can cause a splitting action, cracking the cast mstr cylinder.
I am not saying you did, but if you have, you will have brake fluid spraying out of the crack. (A good indicator) Plus sucking air.
When the treads are cut both on the brass block and Mstr Cylinder, the origin point of the threads is not consistant, so you can have a 1 o'clock start on a brass block or a 6 o'clock start. Any position on a 360 degree circle. When I rebuilt my car, thankfully I had several brass blocks and was able to find one which suited the orientation of the threads and positioned the block in the correct place.
I would recommend a new brass block, and you may get lucky on the orientation.
Also note you may have damaged the old brass block threads, by over tightening, making it impossible to get a seal (destroyed the "taper" threads, which are now flat).
ALSO consider that the photo shows the hydraulic brake light switch is installed and you may have air trapped in the switch, causing part of your grief.
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blab
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Re: Brake bleeding

Post by blab » Tue Aug 21, 2018 9:39 am

Thank you for the possible reasons, that's something I can check. The leak is small, like a small drop after several activations of the master cylinder.

And I'll soak the brake light switch in fluid like the manual recommends.

Next problem: I have to move the car and the replacement block will not come in time. I can get 3/8" T-junctions at a local shop here. Using two of these will give me three outputs. This would be a temporary solutions for about two months. Is this a stupid idea? Will a brake line nut make a seal to the master outlet? The T-junctions only have female thread so I'd have to use a short piece of brake line to connect it to the master.
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Re: Brake bleeding

Post by sseebart » Tue Aug 21, 2018 11:54 am

blab wrote:
Tue Aug 21, 2018 9:39 am
Next problem: I have to move the car and the replacement block will not come in time. I can get 3/8" T-junctions at a local shop here. Using two of these will give me three outputs. This would be a temporary solutions for about two months. Is this a stupid idea? Will a brake line nut make a seal to the master outlet? The T-junctions only have female thread so I'd have to use a short piece of brake line to connect it to the master.
This depends on how far you intend to move the car. If it's from the garage to the driveway, this may work. Anything in traffic . . . probably not.

~Steve

blab
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Re: Brake bleeding

Post by blab » Tue Aug 21, 2018 4:33 pm

OK, I won't do that and wait for the block to arrive. Meanwhile push the car around.

With the minimum line length that my flare tool needs this would not have been pretty.
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blab
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Re: Brake bleeding

Post by blab » Sat Nov 10, 2018 10:59 am

Still working on the master...

Some weeks ago I got a new brass block, but it leaked at the thread where it is connected to the (Raybestos) master too. I then ordered a new master, this time a Centric. I still get bubbles:

https://youtu.be/7pEpnTdhC6s

New master, new brass block.

Could this be normal? Not coming from the brake lines this time, but from a hole in the middle of the reservoir bottom. I wonder if this is by design. Because the piston might be not 100% airtight and this is how it gets rid of the air that enters during movement?
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blab
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Re: Brake bleeding

Post by blab » Sat Nov 10, 2018 12:14 pm

I disassembled the old-old master to see what's going on inside. Will post pics later. I'm pretty sure now the air enters from the front. There is another hole further to the back and there are never bubbles from that hole.

Edit: when I remove the brake pipes the bubbles stop. Have to test more tomorrow.
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blab
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Re: Brake bleeding

Post by blab » Sun Nov 11, 2018 4:24 pm

Took Joe's advice and reduced to one return line. Removing the brass block and connect the line directly isn't possible because the master thread doesn't have a flare. I also made a new flare on a brake line and found a transparent line. So I can see the bubbles now:

Image

I can close the transparent line with a screw and don't get any bubbles. Not sure if this proves anything, the piston movement is very restricted then. But no leaks anywhere. This is brake fluid pressed through the tiny hole:

Image

And the parts (old master here). The seal in the lower right should be the one that fails, when brake fluid leaks into the master:

Image

Image

Check valve at the front:

Image

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I have no idea how to continue. The internet has several references to this problem, some are solved by getting a new master. Others... I don't know. I already got a new master. How likely are two faulty masters?

Also, in the first pic in this post you can see that the amount of air is a lot. There should be a leak where it comes in. Or, if it comes in at the back, the bubbles also should come out of the second hole, here on the right:

Image

Nothing makes sense, very frustrating.
Image
Since 1993.

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