DISC BRAKE CHECK BALL LOCATION

[Rick Allen]

Not sure where this (check?) ball should go.  The book shows it going into the bleeder port of the piston cylinder casting, and the parts page also shows the ball G145647 (illustration #1103-20) as being "for" that fitting 1558070 (illustration # 1103-17).

However, looking at the short section of brake line that connects to the rubber brake line, it's clean that one end is flared for a ball (as pictured)!

So wouldn't that be where the ball would go, in the port of the casting that connects to the rubber brake line/hose?

Also, I assume this ball acts as a check ball, but I don't see how if the line is tight then it would be holding the ball against the port opening?  

[64studeavanti]

It would make no sense to go on the input side. If that were the case, the brake fluid would effectively stop the flow into the pistons, meaning no brakes. 

It does go into the bleeder port. I believe the theory is that it helps prevent air from entering when bleeding the brakes.

[Rick Allen]

10 minutes ago, 64studeavanti said:

It would make no sense to go on the input side. If that were the case, the brake fluid would effectively stop the flow into the pistons, meaning no brakes. 

It does go into the bleeder port. I believe the theory is that it helps prevent air from entering when bleeding the brakes.

Yes, that would make sense, and the larger flare on the short section of brake tubing would connect to the rubber hose,,,thanks

[64studeavanti]

The check ball also prevents fluid from exiting the bleeder screw. When tightened,  the screw contacts the ball which in turn contacts the seat in the piston housing.

[DWR46]

Take out the bleed screw. You will find it has a conical indentation instead of a tapered point. The conical indentation is what presses against the ball to seal the bleeder. Many people lose the ball and then tighten the bleeder super tight to try to stop the seepage. All that does is ruin both the bleeder and the ball's seat in the cylinder.

[Rick Allen]

1 hour ago, DWR46 said:

Take out the bleed screw. You will find it has a conical indentation instead of a tapered point. The conical indentation is what presses against the ball to seal the bleeder. Many people lose the ball and then tighten the bleeder super tight to try to stop the seepage. All that does is ruin both the bleeder and the ball's seat in the cylinder.

So being a special bleeder screw, back when the car was new and for years after, I would imagine gas stations/garages, where most would probably have service done after the warranty, would have these bleeders on hand?  After all, how many cars had disc brakes in those years and those who did, were probably foreign (like the XKE setup on Avanti?,,,

[DWR46]

Rick: Same system as Jaguar and Ferrari in the era. American car mechanics were NOT familiar with the Dunlop disc brake system.