Master Cylinder under dash

[MikeC]

I put a Kugel 90* brake/master cylinder under the dash of my 39 chevy.  I am just about finished and added brake fluid to the remote fills on the firewall.  I am using -3an hoses from behind the dash to the MC and the same flexible hoses from the MC to the brake lines low on the firewall.  I am using DOT 5 silicon fluid.
My problem is I have been screwing with these lines for almost a month now because they are LEAKING somwhere.  My car interior is done and this is really stressing me out!  I keep trying different things but I can't seem to stop the leaks.  I have used teflon tape anywhere that does not have the flair but have not used it with the flared fittings.  It is really tight under the dash and I can not really tell where this is coming from.  Any advice besides moving the MC to under the car where it should have been in the first place.
Thanks
Mike

[Charlie Chops 1940]

Hi Mike,

I'm using a Kugel setup in my track roadster (brake & clutch) and I plumbed it with flared steel line and used DOT 4 fluid. I made a bulkhead fitting at the firewall with brass unions silver soldered in a brass plate. My thoughts were to keep more or less standard fittings involved. I had a couple seepers that went away when I tightened them harder. I have used silicone fluid before but have felt that it can find the tiniest places to get out.

That said, did you buy or make up the -03 lines? Quality adaptor fittings being used? I would  clean up each fitting starting at the MC and then just observe whether anything leaks under gravity,and then pump the pedal and then wipe again using white paper toweling. The greenish/yellow cast of DOT 5 shows up pretty good on the white. I doubt that all of your adaptors and hoses are leaking at every joint so eliminate them one by one. Maybe put some plastic sheeting on the floor with some throwaway towels to soak up any actual drips.

Personally I think you're gonna have some extreme soft pedal issues with DOT 5 and so many braided hoses in the system.

Charlie

[MikeC]

Thanks Charlie,
I think I will get some more stainless tubing and try to re-plumb with hard lines.  It is so difficult to tell where the stuff is seeping from but it is doing it under gravity alone.  I think the Earls braided pre-made is split somewhere.  I never thought about the spongy brake though...hard lines should fix that.
Mike

[C9]

I had silicon fluid leaking at the brass inverted flare union between two hard brake lines.
Didn't make any difference whether it was my double flares or Burndy (brand name) factory flares.
The problem went away when I changed to steel unions.

Seems there will be a minor amount of flex between M/C and the bulkhead fittings and perhaps a hard line shouldn't be used there.

If you do, I think the common Burndy parts house ready made brake lines should be used and coiled similar to what you see under the hood of factory cars.
The coiled section is probaby there due to expansion and contraction of the line due to thermal cycles under the hood, but also helps to help damp vibration in a short line.

Note the small diameter coiled hard line line to mechanical oil pressure gauges.
Done by both the factory and hot rodders.

If you're using a hydraulic stoplight switch - standard issue or the so-called low pressure switches from the hot rod aftermarket - you'll find that silicon fluid emigrates into the contact area.
The silicon fluid insulates at the contact and the switch will take ever increasing amounts of brake pedal pressure before the contacts will pass electricity and light the brake lights.
After a couple of those, I went to a mechanical switch.

Fwiw - I had a knowledgeable been-around-a-while parts house guy tell me that all hydraulic brake switches operated at 7#.

Is there anywhere in the under-dash brake system where a hard line adapts to a flex line?
If so, do you have the proper fitting with the steel button that goes over the hard line and inside the fitting - it pulls the flare onto the inverted seat?

These fittings are usually used where the hard brake lne goes to the (most times a bulkhead) inverted flare fitting that accepts the flex line at the frame . . . front brake lines for example.
Without one you can't pull the flare on the hard line down onto the fitting for the flex line.

Any chance you're trying to pull the hard line onto an inverted flare fitting with an NPT fitting?
Or pull the hard line - with male NPT fitting - onto a female NPT fitting?
This one won't work since the hard line never gets pulled onto a seat like an inverted flare has.

[Charlie Chops 1940]

Good observations by Jay.

I've not had any problems with the brass unions, either with regular brake fluid or silicone...doesn't mean it doesn't happen though.

I have come to truly hate those pressure switches and go for a manual switch whenever possible. The Kugel set up has a GM style plunger mechanical switch. The lever type that mounts under the toe board for through the floor pedals works good too....just have to keep it out of the flow of lots of water.

Keep looking.

Charlie

[MikeC]

C9,
I am presenty using braided teflon hoses (factory-made) (2- Earls and 2- Goodman) from bulkhead fitting from remote fil to M/C and from the M/C to the bulkhead to the brakes (front and back).  No hard lines under the dash to the 90* M/C.
As Charlie said, the Kugel 90* has a mechanical switch but I find it interesting that the silicon wants to creap.
Under the dash the braided lines only go to bulkhead or M/C.  On all my lines everywhere I have used the Earl fitting (button) that pulls over the flair.
All the braided female is being connected to Earl's aluminum flair male.  No NPT in the system.
Thanks for the advice.
MikeC