No Brakes - how hard to replace master cylinder plus lines?, looking for some guidance before I dig into my manuals... Options

[potomacmidget]

Merry Christmas everyone,

So, my brakes have been really soft, and I figured they were due a bleeding so I bought a pressure bleeder (watched Ian Karr video) and put my car on jackstands and removed all the wheels. Topped off the reservoir with fluid, then when I inspected the master cylinder and observed it was visibly "wet" with what I could only suspect was fresh fluid. First thought was "ok, not good, that must be my pedal problem" then I reached in there with an open end wrench to see if I could snug the connection, and the tubing (vertical) was not even connected to the MC, it just swung away when I touched it, then all the fluid poured out. I guess the threaded part of the tubing rotted away in the MC?

Regardless - looks like I need a new MC, and will have to inspect/replace sketchy lines, etc., and all that comes with that project.

Prior to diving into my collection of service manuals, any guidance on the challenges of this job? Do's and Dont's? It looks a bit nightmarish to access the MC, and since my simple job turned a lot harder, I will wait until my garage is warmer than 30F. All advice appreciated...

thanks,
Reg

[gereed75]

Hawk, I get your perspective but I don’t see any reason that the possibility of being in “a bad accident involving brake issues” goes up with a -3AN system. From an engineering perspective it should go down. The AN system has substantially fewer connections than the stock system - like four as opposed to maybe a dozen. Seems better to me.

Any recent examples of this technology being used in OEM applications?

Not at all looking forward to having to drop the rear subframe to replace with stock.

[Superhawk996]

Hawk, I get your perspective but I don’t see any reason that the possibility of being in “a bad accident involving brake issues” goes up with a -3AN system. From an engineering perspective it should go down. The AN system has substantially fewer connections than the stock system - like four as opposed to maybe a dozen. Seems better to me.

Any recent examples of this technology being used in OEM applications?

Are we talking the same AN fittings as shown below?

No OEM is ever going to AN fittings. Cost is one thing. The multitude of failure points within the fittings is another. As far as I’m aware there are no DOT approved AN fittings. No OEM is going to use Non DOT parts.

Now I get the argument that AN derives from mil-spec parts. Despite what marketing may say, are you getting Mil-spec parts in retail? Not likely.

I have also personally used AN extensively in racing. Again, that’s another story where equipment is constantly being maintained and inspected. In the rare event of a failure, all activity is on closed course with willing participants that have signed waivers acknowledging the danger of the activity. Completely different than street use.

[gereed75]

These lines are kitted with factory made fittins and use Teflon lines with braid and then PVC cover, not a DIY AN fitting. They do terminate to the brake system with an adapter fitting.

https://www.chasebays.com/cdn/shop/files/Ch...ng?v=1698182168

Looks pretty robust and way fewer connections than multiple steel lines with a rubber hose termination to the caliper

[Superhawk996]

These lines are kitted with factory made fittings . . .

Yeah - misunderstood what you were planning. That’s better than DIY. Presumably there is some pressure testing and quality control going on there. I didn’t look to see if those particular lines are DOT compliant. There are some stainless flex lines that are. Not sure about these with the AN flare.

Here’s the thing. Controlling a long flex line is not as simple as it seems.

The flex line has to be kept from contacting other parts as wheel cycles from full jounce to full rebound and lock to lock steering. I’ve personally seen instances where the line was too short and was getting pulled under tension at full rebound. Likewise I’ve seen instances where the flex line contacts the tire; the stainless braid quickly acts like a saw.

The flex line has to be kept from resonating and whipping around in the wind, otherwise the line will fatigue and break (eventually). Seems simple to tie wrap it to something . . . Now go back and check to see that you still have full wheel travel and no contact. Usually not as simple in practice as it seems.

Teflon lines require larger minimum bend radius than OEM style rubber flex hose. Trying to not bend lines too tightly while avoiding the other rubbing and resonance issues results in long(er) flex lines.

There are advantages to the way the OEM lines are routed. Steel lines will always have less expansion than teflon/stainless braid flex lines and is going to be better brake feel and performance.

Modern low expansion rubber flex lines are much closer to the expansion of teflon / stainless steel braided lines than they were back in the 80s.

All things to consider.