Mustang master cylinder question - '94 / '95 style

[Gumball]

I have an interesting issue with my master cylinder. It's a new part that I bought through FFR during my build. No issues with leaks or anything at the m/c itself, but I have a weird problem (maybe an unintended consequence) that is occurring at the reservoir cans. The rear one - which feeds the front brake circuit - is overflowing.... even though they started out both even at about 2/3 full. This has happened twice now, and both times the front can (which feeds the rear circuit) is down by the same amount that the other can is overfilled.

The original plastic reservoir that came with the m/c was a single upper that was divided by two "funnels" that then went down into the m/c. The only thing I can think is that the m/c has some sort of shuttle valve in it that was intended to recirculate some fluid back through the rear and into that main plastic reservoir - meaning that in the event of fluid running low, the front brake circuit would get the majority of the remaining fluid... ensuring that the front brakes have a better chance of being there when an owner lets the fluid get too low.

As mentioned, no outward signs of leaks and the brakes work fine.

Thoughts?

http://i845.photobucket.com/albums/ab15/CCRsAC/img_4047.jpg (http://s845.photobucket.com/user/CCRsAC/media/img_4047.jpg.html)

Here's what it looked like before removing the stock reservoir - from this pic, it would appear that the reservoir wouldn't care whether the fluid returned through the rear or the front. I'm at a loss - absent there being some internal flaw where a seal is bad.

http://i845.photobucket.com/albums/ab15/CCRsAC/master%20cylinder%20OEM_zpssb3agzqi.jpg (http://s845.photobucket.com/user/CCRsAC/media/master%20cylinder%20OEM_zpssb3agzqi.jpg.html)

[Jstanding]

Any luck? I like the look of that reservoir setup. I'm interested to see if you get it going correct as I would like to find something like that.

[Jstanding]

is there enough slack in the lines to swap the lines on the cans and see it is the orentation of the cans that is causing the level indifference or if it is the M?C that is doing it? If that makes any sense.....

[prophet]

There might be a shuttle valve in there. Does the MC have a port for a pressure sensor that would trip a warning light? If so, the problem might not be the valve or the MC, but somewhere else in the system. What happens if one side has a pressure loss for whatever reason, the shuttle valve kicks over so the healthy side gets the majority of the fluid and pressure.

[avgjoe]

What did you find out about this? Over the winter I am planning on adding remote reservoirs to my Mustang M/C.

PS: Was that you at Autobahn a few weeks ago?

[Gumball]

Joe,

Yep - I was at Autobahn a couple of weeks ago... a friend of mine and I are instructors and he now owns my old Bondurant Mustang (#74). I live nearby and felt like visiting my old car - sort of miss that war horse.

My research on the M/C was inconclusive, but it seems that there is some sort of shuttle valve in it that would not be an issue with a common reservoir. My work-around is to just check the balance occasionally and move the fluid using a turkey baster until I can do a fix that will involve interconnecting the cans or supply lines.