Hey guys, I've searched this topic and read a lot about this metering valve. I'm having problems bleeding my front brakes, and after reading posts I'm thinking my problem may be related to not pressing this button while bleeding the brakes. I've got factory disc front and drum back.
I've replaced the booster and installed a reman. master cyl. I've bench bled the master twice. The rear brakes bled good, but I'm getting some bubbles back into the master, and lots of air out the bleeders on the front circuit.

I've read conflicting info regarding this button on the rear of the metering valve. Some say it has to be held in when bleeding, and some say not to hold it in. I am using the conventional bleed method of holding down on the pedal and open the bleeder, then close bleeder and release the pedal. I also hear that a special tool is used to hold the buttom open.

Can anyone clarify if I need to hold this buttom open when bleeding? - and if so, what is this special tool? thanks.

You only need to press the button when using a pressure bleeder. If you are manual bleeding that develops enough pressure to overcome the valve and push fluid through it.

I think the shop manual shows a special Kent Moore tool to depress the button, it needs something strong to hold it down, you can't do it with just your fingers.

I'd try going back and loosening then re-tightening all the hyd fittings, sometimes they don't seat right and can suck air.

Some master cyls don't come with the brass flare seats pressed in all the way and don't really tighten up right on the first try.
David

thanks for your expert suggestions David; I'll do as you suggest and try again.

Sort of a dummy check on my patr but, I recently had a similar problem, Turned out I had the calipers mounted on the wrong side of the car. The bleed nipples were at the bottom instead of the top of the calipers, the trapped air wouldn't move. They wouldn't bleed right no matter what I did. Switched them right to left and worked fine. May not be your problem, but worth a look.

JRQUINN,
That's a somewhat common problem, especially when the calipers were borrowed from a front steer car. Front steer calipers sometimes have LH and RH cast into them but must be reversed to work on a rear steer car and still have the bleeders pointing up.

well guys, I've got the calipers on the right sides - all connections are tight - bench bled the master twice - hoses don't appear to be collapsed - metering valve is working properly when the brakes are applied - AND STILL TONS OF AIR AT THE BLEEDERS!!! even after bleeding 20 times.

Now when my son holds on the pedal, and I loosen the front line at the master, I occasionally don't get any fluid coming out of the master??

If you have a clear hose over the bleeder and see bubbles, it may be sucking air past the threads. Put some teflon tape on the bleeder threads to eliminate that.

Do you have any pedal?

some restriction on the pedal, but it will go to the floor

Try putting some vise grips on the front and back flex hoses and then see if you have a hard pedal, if you do you have eliminated pretty much everything up to the hoses. Just use enough pressure on the vice grips to gently close off the hoses.
If the pedal is hard, have someone release the vice grips 1 at a time until the pedal goes way down, and you have found the problem area.
We use this trick on Corvettes all the time at the shop and it works pretty good to find the culprit caliper or line etc.
Hope this helps. Mike.

Thanks for the help Mike - I'll give her a go. Confirming it shouldn't matter that the engine is not running while bleeding??? (motor is out of the car)

Motor does not need to run.

I was having the same problem with air in the front brakes. When I bypassed the hold off (metering) valve the problem disappeared. I used a short length of steel line to bypass it.

The valve was not leaking fluid but was sucking in air! I intend to replace the seals in the valve someday, but it is not a high priority as the car stops fine without it.

Interesting - thanks guys for all your suggestions. I bought new bleeders today, and will try them tonight.... and now have other avenues to pursue.

Hey Farm Boy - I think you directed me in the right direction. I replaced the bleeders - no luck after many attempts. I removed the metering valve and by-passed it with rubber hose. They bled-up shortly after. Athough I still have little peddle; no air is coming out. I suspect when I install the motor and start her up; I'll have more peddle... I hope. Any other comments or suggestion??