Dual Master Cylinder Conversion

[redfalken]

Never put anything like teflon tape or pipe dope on flared fittings. The seal is made when the nut presses down on the flare. If you look at the female half of the fitting you'll see where the flare seats and makes contact when the nut pushes down on it.

The threads on the nut don't need to be sealed because if fluid is getting past the flare seal, you need to snug it a little tighter or make sure the double flare looks like it's correct.

[Jeff W]

I think the NPT threads on the brake light switch would need some teflon tape.

Did you get different T fittings than the guys you described? I'm still not clear on the adapter to T connections. Although if may feel like NPT and straight threads screw together... it is not correct.

[ew1usnr]

Did you get different T fittings than the guys you described? I'm still not clear on the adapter to T connections. Although if may feel like NPT and straight threads screw together... it is not correct.

Wikipedia says: "National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal."

Hello, Jeff.

Due to parts availability, I used two different-sized adapters for the master cylinder outlets with male NPT threads and flaired female threads. The fitting on the left goes from a 1/2" hole to a 1/4" brake line. The one on the right goes from a 7/16" hole to a 3/16" brake line.
2-DCP_4823.JPG

Tee #1 was complicated because it joins two different sized brake lines and the brake-light switch. Tee #1 seems to have three female NPT inlets. The brake-light switch and the two flaired adapters feel like they are screwing in correctly.
1-DCP_4822.JPG

Here is a side view of the complicated Tee #1. You can see the flaired fitting on the inside of Tee #2 in the background.
3-DCP_4824.JPG

[ew1usnr]

Whoops! I just spotted a potential problem.

These are the adapters that screw into the master cylinder inlets.
1-DCP_4826.JPG

In my previous post I had called them NPT pipe thread fittings. But, .... they screw into holes for flair fittings. The smaller fitting on the left has a dish-shaped end, so it should be good for its flair coupling. The one on the right has a flat end that must be for a pipe thread and it needs to be made for a flair fitting.

UPDATE:
I got into the Zone, ... Auto Zone.

I replaced both of the couplings that screw into the master cylinder. The new one on the left has a longer shaft ($2.49). The one on the right now has the correct flair fitting on both ends ($1.99).
1-DCP_4827.JPG

Here are what the new couplings look like:
2-DCP_4833.JPG

[redfalken]

If you do have to use sealant on any of the NPT threads, be careful to not get anything past the end of the nut. You don't want a piece getting into the system. I've heard Permatex Thread Sealant is resistant to brake fluid and may be a better option. The white teflon tape just turns to goo if you get brake fluid on it.

I've just done everything possible to never use sealant on a brake system. I got rid of the pressure light switch by putting a mechanical one on the brake pedal under the dash.

[Jeff W]

I think that all should work. Let us know if you have problems. Now that you are a Rainier member we can send you any needed fitting. Labor is a bit of a challenge considering your location.

[ew1usnr]

A final (hopefully) revision:

After further reflection, I decided that it would be better to eliminate the two NPT adapters on the brass tee for the brake light switch and bought an “Allstar Performance 3/16" Inverted Female Tee Brass 3/16 Tube T 1/8 gauge port” off e-bay for $8.49 + free postage. Manufacturer's part number: ALL50137. I hope that this is correct.
http://www.ebay.com/itm/190998743464...84.m1497.l2649
Allstar 3-16 plus 1-8 NPT Tee.jpg
angle photo of tee.jpg
I also bought a “brake line adapter for master cylinder 9/16” 18 thread male X 3/8” 24 female adapter” off e-bay for $6.80 + $3.08 postage, to allow me to run a 3/16” brake line from the large hole on the master cylinder (a 3/16" fitting has 3/8" -24 threads). http://www.ebay.com/itm/BRAKE-LINE-ADAPTER-FOR-MASTER-CYLINDER-9-16-18-male-X-3-8-24-female-/231006105707?pt=Motors_Car_Truck_Parts_Accessories &hash=item35c909706b&vxp=mtr

BRAKE LINE ADAPTER FOR MASTER CYLINDER 9-16 18 male X 3-8 24 female.jpg

[Jeff W]

Now I feel much better This is a good set -up.

Everyone can (and is allowed) to do their own thing, but less Rube Goldberg is best when it comes to safety.

Be sure to:
1) use the push rod out of your old master cylinder. It usually takes some muscle to get it out. The new rod is too long.
2) bench bleed the new MC before installation.

Wikipedia says:
"Reuben Garrett Lucius "Rube" Goldberg (July 4, 1883 – December 7, 1970) was an American cartoonist, sculptor, author, engineer and inventor. He is best known for a series of popular cartoons depicting complex gadgets that perform simple tasks in indirect, convoluted ways..."

[Luva65wagon]

Noticed the earlier image showing the nut hard-up against the M/C and was going to (prematurely) comment, but decided to read through all the rest. You seem to have it all figured out using the correct adapter fittings.

Having now done about a dozen of these conversions it's so much easier to do than it is to explain. I/we should really do a full-fledged PDF of this step-by-step with detailed pics. The original PDF posted is good, but leaves out a couple important details, like these fittings for one - or the use of 3/16 brake like (which normally comes with the 3/8-24 threads), but adapting them to the two larger nuts. Or options to negate the pressure switch. Real soon now.

And, now, just to clarify fittings and their use... pipe threads are tapered. The teflon or "sealant" are not supposed to act as the seal. The taper provides this. The issue is keeping friction low so you can force the two threads together until they self-seal before they gall (the melting, of sorts, of similar materials by heat or friction). On some materials, like stainless, these similar materials will gall very quickly without a sealant with Teflon, and in some cases still will to some degree. So the use of a Loctite-based Teflon sealer will cure and harden in the absence of air and minimize leaks. Usually the use of sealant, as a sealant, is deemed necessary when the male and female parts have worn or expanded beyond their wear limit - with mixed results.

Teflon tape, if used, needs to begin up about one thread from the end of the male threaded end to keep it out of the system. But great care needs to be given if Teflon tape has been used before. Every strand of it needs to be removed, since even though it is used correctly the first time, the second use of the threaded parts will work these strands forward and inward - towards the flow of fluid - and into the working bits.

Inverted flares need no sealant, as Kenny indicated. The flare (male against female) cause the seal. One issue I have seen when using these large nuts but with 3/16" line size is that the male part (like that inside the M/C) is assuming the larger tubing flare, not the 3/16" size flare. I had one install where I could not get a good seal. So - just putting this out there that it "may be" better to use the adapter fittings as opposed to the large nuts with 3/16" holes. Depends on the machining of the flare inside the M/C.

Since flare fittings don't expand with use, like pipe-thread fittings do, they are a positive seal every time you loosen and tighten them.

So that's all I got to say about that. Happy braking!

[ew1usnr]

Hello, Roger.

You talked about lubricating pipe threads. Would dipping the brake switch threads in brake fluid work?

I made another revision yesterday. I went to NAPA and bought two "Brake Fit Tube Nuts" (#641-3296 and #641-3322) for 69 cents each and then went to "Just Brakes" and had them attached.
brake lines.JPG

The mechanic used a tube cutter to cut the ends off the brake lines. He re-flared the lines with a "bubble flare" and said that this was the flare that my 8-inch brake lines had come with. I made a brief look at the internet about the subject and saw the comment: "Automotive brake lines are always a 45 degree double flare or a DIN (bubble) flare." Here are my bubble flares:
fittings.JPG

Here is an internet photo comparing the bubble and double flares. I need to read more about the difference between the two:
bubble flair and double flair.png

Here are what they look like attached. This eliminated two adapters. If the custom flare fittings leak, I can always get a couple of new brake lines and try the adapters.
on master cylinder.JPG

[Luva65wagon]

I've never seen bubble flares on a car before, so I'd need to study those too. Our cars used 45 double flares.

As for brake fluid as a lube, as long as when you tighten it, and all is said and done, if you don't have any hint of a leak, you're probably OK.

Happy new year - there.

[redfalken]

I've never dealt with bubble flairs but they came into standard in the mid-80s. Maybe even in metric systems. Do they use the same fittings as the double flair?

[ew1usnr]

A NAPA shop near my house has a machine shop. I will visit there tomorrow and see if they can put a "45 degree double flare" on the ends of the brake lines.

Description read on internet: "Inverted Flare or 45 is on all standard automotive applications, and cars and trucks from the 30's to mid 80's have inverted flare fittings at all the connections. Inverted flare is a single nut that uses a 45 degree double flare. This flare is lapped over so the tube is double thickness at the end."

See: http://inlinetube.com/install%20instructions/Instruct%20tube%20flaring%2045.htm

[redfalken]

For about $50 (on the cheap end) you can get a double flaring tool kit and pipe cutter. I've always flared brake lines myself and think it's really easy. After watching some YouTube videos and practicing a few times, it's not difficult to get the hang of. And you'll have the tool when you need it again. And you will probably need it again down the road.

Old lines tend to seize to the nut and will twist as you try to remove them. The wheel cylinders are notorious for this and if they are original, you should put them on your list of things to replace. That's what blew out on Jeff's wagon. Even with a dual master cylinder, the rest of the system should be tended to. Check the rubber hoses going to the front wheels and rear distribution block on the differential. If they're getting dry and cracking...replace.

[BadBird]

If you decide to buy a double flaring set, I would advise you spend a few extra bucks and buy a good quality brand. Search the internet on what is the best for the buck. I bought a cheaper version and the flares were bad and leaked. Bought a better set and they work great. I agree with Kenny that it is a good purchase and the tubing cutter along with a decent tubing bender will get used again and again. Larry