The two bleeders Options

[emerygt350]

I just popped on my newly remastered rear brake calipers from PMB and was wondering if there was a point to the lower bleeder? I only ever bothered with the top bleeder before but now that it's bone dry I was wondering if that might be why the second bleeder exists? I will be bleeding the brakes tomorrow morning.

[davep]

Dual bleed nipples of the 914 rear have nothing to do with handedness, the parking brake lever defines that.
However, I have found that when doing an annual fluid bleed it is often better to open both bleed nipples to fully drain the calipers before refilling. Forty years ago I had to start rebuilding the calipers to keep them fully functional; there was no PMB to send calipers to and there were no (!) parts available in any case. Taking the pistons out was a real eye opener since the outer pistons were always filled with more crap than the inners. The reason for this is simple. The fluid inlet is on the inner side of the caliper as are the bleed nipples. When you do a quick flush and bleed the fluid enters the inlet and heads straight for the open nipple. This does not flush the fluid inside the pistons, particularly the 914 rears with the adjuster mechanism inside, and it certainly does not do much of a job in circulating to the outer half of the caliper. The result is that old fluid is retained inside the pistons and most of the outer caliper half with a quick flush and bleed. Hence my method was to drain the calipers first, then do a complete refill and bleed. Every few years I would disassemble the calipers to thoroughly clean inside to keep them operating efficiently.

[930cabman]

Dual bleed nipples of the 914 rear have nothing to do with handedness, the parking brake lever defines that.
However, I have found that when doing an annual fluid bleed it is often better to open both bleed nipples to fully drain the calipers before refilling. Forty years ago I had to start rebuilding the calipers to keep them fully functional; there was no PMB to send calipers to and there were no (!) parts available in any case. Taking the pistons out was a real eye opener since the outer pistons were always filled with more crap than the inners. The reason for this is simple. The fluid inlet is on the inner side of the caliper as are the bleed nipples. When you do a quick flush and bleed the fluid enters the inlet and heads straight for the open nipple. This does not flush the fluid inside the pistons, particularly the 914 rears with the adjuster mechanism inside, and it certainly does not do much of a job in circulating to the outer half of the caliper. The result is that old fluid is retained inside the pistons and most of the outer caliper half with a quick flush and bleed. Hence my method was to drain the calipers first, then do a complete refill and bleed. Every few years I would disassemble the calipers to thoroughly clean inside to keep them operating efficiently.

Thank you for clarifying this, the dual bleeders have been a mystery for me and I am sure many others.