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Discussion Starter · #1 ·
I'm using a stock late model Cobra Hydroboost unit with the stock distribution block in my MKIII. I connected the 3/8 lines to the distribution block using M12 & M10 male bubble flare to 3/8 female adapters like the one shown in the link below:

Adapter

I'm getting brake fluid leaking from around the threads of the male portion of the adapter where it screws into the distribution block. I've cranked on them as tightly as possible using line wrenches, so I know they are tight. The fluid is leaking from the threads of the adapter and not the actual 3/8 brake line or fitting.

Can I just use some sort of sealent on these threads to seal them up? I know everyone says not to use teflon tape, but in this application can it be used?

See picture below showing where the leaks are.

Thanks

- Colby

Click for larger picture
 

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Senior Member
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1,595 Posts
You should not have to use anything on those threads. The taper on the adapter should seal to the block.

Bill G
 

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I accidently cross-threaded one of my brake fittings into the ABS block. I took it to a machine shop and they retapped the female end and it then tightened up. I also found that the FFR supplied fittings were not matched to my car and instead used the donor fittings.
Good luck.
Art
 

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Discussion Starter · #5 ·
I purchased the adapters from Disk Brakes-R-Us after calling them and confirming what I was going to use them for. The complete description of the fittings are:

FITTING 3/16 X 12MM x1.0 to convert Bubble Female in master Cylinder to Double Flair for steel lines for Aluminum Master Cylinder.

As shown here:




The distribution block has the same ports as the actual master cylinder.
 

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FFCobra Craftsman
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This may sound odd/silly, but loosen the fitting up and then retighten it. This often works on steel lines that have just been flared. The last time it happend to me was a fuel line going into a carb. Fuel was going everywhere from this new fitting. I loosened, wiggled, retightened and no more leak.
 

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in order for brake line fittings to seal properly under pressure the male and female ends must be the same type of sealing surface(mostly single or double flare). I had to go thru quite a few drawers at the auto parts store with the parts in my hand to find the ones that fit properly. since the seal is supposed to be between the line and the fitting and the threaded nut is only applying the pressure teflon tape is not your answer, the seal has to be inside of the threaded parts. The most likely cause of your leaks is mismatched sealing surfaces. take them apart and compare them carefulluy they should look like reverse images of each other, one concave and one convex(one inny and one outie) to seal.

Frank
 

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Discussion Starter · #8 ·
Frank, thanks for the reply.

The distribution block requires a bubble flare, which the adapter has on the male side. (exact inverse of port in the block). The adapters I purchased not only change the size from M12 (and M10) to 3/8, they also convert the flare type from bubble flare to Double flare.

Your right about the fitting transfering the pressure to the line, that's what its supposed to do. However the weak point (leak) in the fittings are at the male end where it screws into the distrubution bock, and not the female side where the 3/8 brake line and fitting is connected. it seems the problem is with the seal between the adapter and the block.

[ December 27, 2006, 12:47 PM: Message edited by: ccorso ]
 

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I too had the problem wehre I loosened the fitting turned the brake line ever so slightly and retightened it to stop it from leaking. Take your time get this right...you may need those gadgets some day..
CalHusker
 

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Official OLD GUY
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NEVER . . . let me repeat that, NEVER use Teflon on brake lines! ( or any type of sealer )

Brake lines are designed to be self sealing in and by their design, double flare (or bubble flare). If done correctly, they will seal the first time and be able to withstand the pressures of a normal brake system for many years.

Make sure the nut pressing on the double flare is the correct one if you made your own brake lines (inverse flare or bubble).

Make sure the "adaptor" is seated all the way down into the block. Just because you used flarenut wrenches to tighten them down doesn't guarentee its seated . . . seen too many adaptors that are "wedged" into place and are tight but never seat properly.

HTH

Doc
 

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Colby?

Any leaks from the master cylinder adapter fittings?

If not, ditch the stock proportioning/distribution block.

You don't really need it, as it will not help to balance your front/rear brake balance, and the safety aspect of the 'shuttle valve' is really just an EXTRA safeguard against a line failure.

The standard Mustang MC has a dual reservoir type of system (even though there is only one fill point). It uses internal baffling between front and rear compartments to be sure a line failure does not empty the entire MC which allows at least one circuit to function if a front or rear line fails.

I've heard the safety mantra before as well, and I don't think there is any unusual risk in deleting this item.

...followed by the usual legal disclaimer blah, blah, blah...

Sean
 

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Colby, I hate to say this but you might have tightened them to much. Part of the problem with this type of adapter is when tightened the sealing surfaces are turning against each other which can sometimes cause them to gall. Unlike the tubing ends that are just pressed together. I'd take them apart and check the surfaces. HTH Dave
 

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ASE Tech & Shop Teacher
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Yep, SAFETY, SAFETY, SAFETY!!! Make sure the adapter is taking you whare you want to go. I remember having this problem when GM and Dodge started going metric bubble flair with the brake fittings in the '80s. All I could buy was english threaded double flair lines, so at first, replacing rusted out metrics took a long time due parts house runs for correct adapters. There are even different metric thread counts out there along with both bubble flair metric AND double flair metric fittings. German ones, Japanese ones, Chevy ones, Ford ones, Dodge ones, blue ones, red ones, green ones!! Get the picture?
I started keeping my own stock of sizes, types, and legths that were popular rust outs to speed up my productivity and eliminate the adapters. As I recall some english threaded male ends would actually screw into a metric hole, BUT strip out from being slightly smaller. This is one area you don't want thread sealer of any type. It gets in the system and contaminates the fluid and chunks of tape can clog valves and fittings in the system. If the hardware doesn't seal by itself either the hardware or tech has failed.
 

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I states in your post MASTER CYLINDER FITTING ADAPTER. You are putting it in the distribution block. Is it the right fittig for the job. We never run adapters of any kind. No unions. Hardware with fitting then line to other end then another fitting. No need for the dist block with all discs. HTH, Cheers Richard.
 

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Discussion Starter · #15 ·
Sean - I don't have any leaks from the master cylinder, however I'm using the short stock lines that run from the MC to the distribution block. I just used the adapters to go from the out ports on the distribution block, to the front and rear lines. The only thing I can think of is maybe the adapters are a little long, I believe the ports in the MC are deeper (more threads, not the flare) then the ports in the distribution block. Maybe they were designed to be screwed into a deeper port possibly??

The only reason I kept the distribution block was purely for the safety aspect of it. I thought that because the MC (it's a 02 cobra Hydroboost MC) only had one reservoir, that it required a "safety block" to protect against a line failure.

Can anyone confirm that the stock mustang cobra Hydroboost MC has this protection internally? If so I'll just ditch the distribution/safety block and be done with it.

- Colby
 

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Colby,

Check out dv/dt's pic and explanation down the page on this link:

shuttle valve etc.

If you believe his explanation (I do), then the one 'safety' aspect of the shuttle valve is to divert fluid around the proportioning valve in the event of a front brake line failure. So it's only real function is to prevent the proportioning valve from decreasing rear brake pressure when it is needed most (if the front brake line broke). If you 'gut' the proportioning valve, (as many recommend) then the shuttle valve no longer serves ANY function.

It is the baffles in the MC (see dv/dt's pic in the link above) that keep each system seperated and prevent the MC from emptying both compartments due to a failure of a line at either end.

I like Richard Oben's solution the best (don't use adapters), but that means you need to find someone who can do bubble flares on your MC line ends for you (it is a different flaring tool) or use a different MC. I used adapters on my MC and they seemed to work OK, but I haven't got power to the booster yet.

Your's look similar, but here are the Weatherhead fitting part number's I used:

M10 X 1.0 to 3/16 #1442

M12 X 1.0 to 3/16 #7936

(mine is a 96 Cobra hydrobooster and a 96 GT MC)

Sean
 

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FFCOBRA MASTERCRAFTSMAN 5626
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Make sure the lines are going in straight. I had one fitting that oozed a little. The line was just a little askew. Straightened it , oozed stopped.
 

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Discussion Starter · #18 ·
Thanks for the link Sean. After reading dv/dt's explanation it makes sense that if you take out the proportioning function of the block (which I had planned on doing) then in a line failure the block really would serve no purpose.

So I guess I'll just eliminate it and be done with it.

Thanks!

- Colby
 

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Building
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833 Posts
I just finished setting mine up last night... & doing the long runs today to rear.

2002 Hydro-booster + distribution block & adding Variable Adjuster to rear line.

I needed:
4x 12mm x 1.00 Bubble adapters to 3/16" Flare
(Block had 3 + 1 off the HB)
2x 10mm x 1.00 Bubble adapters to 3/16" Flare
(1x Block + 1x HB
All my lines are now 3/16 Double flare

Ron
 
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