front calipers w/ 2 bleeding screws vs. w/ one screw...

knabini · Post by **knabini** » Fri Apr 21, 2006 7:40 am

i've 1973 and old calipers had 1 bleeding crew on each. The rebuilt units have two screws on each. Should I just ignore the bottom bleeding screw and bleed system as normal? Thanks for any advice.

Rouser914S · Post by **Rouser914S** » Fri Apr 21, 2006 1:34 pm

Start bleeding with the lower bleed screw, than move to the upper bleed screw.

The two screws just provide for a more thorough bleeding routine.

knabini · Post by **knabini** » Fri Apr 21, 2006 2:10 pm

thank you.

raygreenwood · Post by **raygreenwood** » Sat Apr 22, 2006 7:16 am

Actually the lower bleeding screw is for system draining . Since the bubbles move/float upward...the top bleeding screw is for normal bleeding. When teh calipers are brand new as they are with yours....and you get that air bubble lock syndrome....Rouser is indeed right. Start at the bottom and get the big bubble out. The top one should then be used only. Ray

knabini · Post by **knabini** » Sat Apr 22, 2006 5:02 pm

Thank you, guys. When it will be sunny in NYC, I will put them back.
I also need to grind the disks smooth and I know that you all recommend to replace the wheel bearing. Do I really need to do that if the wheels have no play? I know that I will need the seals (ordered).
anyway, all this will happen next weekend.

raygreenwood · Post by **raygreenwood** » Sun Apr 23, 2006 3:03 pm

Replacing the wheel bearings is very simple...and if you have them off...it would be a waste not to. I would stay away from teh chinese wheel bearings. They are machined well...but the cage metal is suspect. They do fine on a modern car whose brakes are oversized and well vented.....but they do terrible on solid rotor older systems. Ray

davidsigouin · Post by **davidsigouin** » Sat Oct 14, 2006 5:21 am

I am not sure if it applies to 914 calipers {haven't seen any} but most calipers that I have dealt with that have 2 bleeders, it is to reduce part number inventories as they are interchangeable from left to right. The second, lower, bleeder becomes the upper bleeder when used on the oppoaite wheel. VW type 2 calipers are like this.

raygreenwood · Post by **raygreenwood** » Mon Oct 16, 2006 6:46 am

Probably also a good use, but most VW factory manuals also specifically list that the bottom screw is there for draining the system prior to disassembly. You crack the top screw as a vacuum breaker and open teh bottom and the system will be substantially drained in no time. Ray