[badahm]

Rear wheel cylinder leak on my '73 Firebird has caused pin in metering part of combination valve to pop out. I have tried unsuccessfully to reset with front then rear bleeds cracked open. Pin won't move. Any tips? Then to bleed repaired rear brakes, I understand that pin has to be held in with a special tool during bleeding process? Usual Pontiac suppliers do not have the tool. Any ideas where to find the tool or what is another way to "skin the cat"?

[Murf'sDad]

Originally Posted by badahm

Rear wheel cylinder leak on my '73 Firebird has caused pin in metering part of combination valve to pop out. I have tried unsuccessfully to reset with front then rear bleeds cracked open. Pin won't move. Any tips? Then to bleed repaired rear brakes, I understand that pin has to be held in with a special tool during bleeding process? Usual Pontiac suppliers do not have the tool. Any ideas where to find the tool or what is another way to "skin the cat"?

All I've ever done after I finish the repair and close the system is hit the brake pedal a couple of times. This resets the valve and then you can fully bleed the system. Might not be the right way but it worked for me.

FWIW, Stewart

[Schurkey]

Originally Posted by badahm

Rear wheel cylinder leak on my '73 Firebird has caused pin in metering part of combination valve to pop out. I have tried unsuccessfully to reset with front then rear bleeds cracked open. Pin won't move. Any tips? Then to bleed repaired rear brakes, I understand that pin has to be held in with a special tool during bleeding process? Usual Pontiac suppliers do not have the tool. Any ideas where to find the tool or what is another way to "skin the cat"?

TOTAL WASTE OF TIME. Forget the pin even exists.

1. The pin did not "pop out" because of some failure. The pin is NORMALLY out. Would be held in for bleeding by special tool--a spring clip. Or by having a helper push it in with his finger. Or by leaning a screwdriver against it, and being careful to wedge it in "just right".

2. The pin controls fluid flow to the FRONT brakes. Has NOTHING to do with REAR brakes. The only time you'd even consider screwing with the pin is if you couldn't get fluid out of the FRONT brakes. If you have fluid flow to the front brakes, you do NOT need to mess with the pin.

3. Holding pin "in" to bleed the front brakes is ONLY needed when using a low-pressure "pressure bleeder". Bleeding by pumping the pedal, or bleeding by gravity does NOT require the pin to be held in. Truth is, I have NEVER needed to dick with the pin even when pressure bleeding. NEVER EVER. NOT ONCE.

[JJKJ]

Good info. Thanks to the OP for asking the question and the answers. I just replaced my mastercylinder and need to bleed the brakes. I read the service manual just to make sure there were no quirks to bleeding the system. Found the info on the pin and had the same questions. Good to know I don't have to mess with it.