New Old Stock is more often than not, mis-leading-mis-guided for parts like brake master cylinders and others that have soft parts like seals that degrade over time.
Parts such as seals can and do degrade over time from simply sitting around.
The only way one will know if the replacement cylinder or cylinder that was removed is OEM is to take it apart and have a look-see.
This is what the innards look like:
http://xwebforums.com/forum/index.php?threads/21003/
OEM bore diameter is 3/4". Deviations from this bore diameter will alter brake performance.
As for leaking brake fluid feed fittings, The fitting OD should be about 13mm. If they are significantly smaller in OD, the seals do not fit properly resulting in leaks. If there are mould seam flash or damage from removal or such on the area where they meet the seals those can cause leaks, if the seals are in poor condition or inferior material this can cause leaks.
Feeder fittings appeared with 6mm and 8mm ID hose as stock depending on year and what Bertone-Fiat had available to install at time of assembly. This why some aftermarket replacement cylinders have an alternative set of fittings in the box.
If the brake fluid feed is leaking, the leak will tend to suck air into the brake system causing a soft to poorly functioning brake pedal-system.
Be really, really careful with any current or "Aged Old Stock" replacement master cylinder as they can be of very questionable quality. Long gone are the days when one can stop in at the Fiat parts counter and get a new OEM master cylinder for low cost that last for decades when properly cared for.
IMO, the only way to really ascertain the quality of a master cylinder is to have the OEM unit sent out to be sleeved in stainless steel (not brass) replace the worn piston with new and new known quality seals. Once it is cylinder is put back together pressure test it for sealing and operation.
This is another situation where market value of the exxe has affected available parts quality.. and what some folks are willing to pay for replacement parts. $150 USD for a exxe master cylinder will be too much for some while $150 for a Ferrari or Porsche 911 brake master is perceived as an absolute bargain.. even if the master cylinder is of identical quality inside and outside.
Friend is currently putting the brake system back together on a Lambo Miura, it has the same seal type and piston/cylinder design as used in the Fiat... except the cost is a LOT higher to get a replacement.
Bernice
But I think the master I got was NOS from Rock Auto and the Inlet fittings were too big so I had to switch out to the ones from the old unit.
I haven't even checked yet, but pretty sure that's what is leaking.
There's not really that much pressure on those seals, so I've been contemplating cleaning everything off really well and spraying the whole unit with FlexSeal.
But first, I gotta test it's resistance to Brake Fluid.
