New Master Cylinder different to Original ?

[JASPER_40]

Hi Betaboyz,

I have replaced my original factory Master Cylinder with a new aftermarket one which doesn't have the screw-in locating pin on the bottom of the cylinder body, used to limit the movement of the front circuit piston.

Is the new MC a revised design but works the same as the original ?

Does anyone know how the front piston is retained instead. Maybe an internal circlip ?

I have also since aquired another brand new MC from a different source and this also doesn't have the screw in locating pin either.

Both new MC's otherwise have the same external specs incliding the depth of the plunger tube.

Anyone know anything about this ?


Cheers,

Steve

[JASPER_40]

In order to test the comparative operations of both old and new master cylinders, I made up a test reservioir using an old brake fluid bottle and some connections that I had 3D printed. Also printed some bleeder connections in order to pipe the outlets back to the reservoir and bled the master cylinder.

I was then able to test the MC's to see if they were fully functioning Duplex by capping off one outlet at a time leaving the other circuit outlet "open" and piped back to the reservoir. I found that capping off the front circuit oulet only allowed approx 60% of the full depression of the plunger. Capping the rear only gave about 75%.

Therefore the Master cylinders were fully functioning and the seals were good.

What was interesting was that I found that using a "reverse bleeder" directly connected to the MC outlets cleared the very last remaining air in the chambers that the standard bench bleeding missed. I doubt that this amount of residual air would make much difference but just goes to show the effectiveness of reverse bleeding.

The stream of tiny bubbles coming back into the reservoir during reverse bleeding also serves to establish that the seals are good in the MC as the air in the chamber is forced past the seal breaking a larger bubble into many tiny bubbles (froth like). A compromised seal would create far bigger bubbles or create a gushing fountain of brake fluid in the MC.

Learned loads from this excercise about the cause and effect of the MC operations. 

Bottom line is that the old style MC with the stop pin for the front circuit functions the same as the new style without the pin.

Cheers

Steve