69 Chevelle SS front brake bleeding

[m22mike]

IMO, pushing on the shaft only increases the pressure on the piston seal, that is under spring pressure and seated and holding off flow. As the brakes are applied the rear brakes see pressure first, as pressure increases to about 40psi it overcomes the spring pressure in the ROUND HOLD OFF VALVE. Fluid flows into the line at the big nut , passed the piston seal, out the side fitting to the distribution valve, to the front brakes. Sometime watch the shaft move out as the brakes are applied by a helper.
If you wanted free flow through this valve it seems to me one would pull and hold the shaft open to unseat the piston seal.
Open to learning more if this sounds incorrect to others.

Mike

['69Novajoe]

Originally Posted by m22mike

IMO, pushing on the shaft only increases the pressure on the piston seal, that is under spring pressure and seated and holding off flow. As the brakes are applied the rear brakes see pressure first, as pressure increases to about 40psi it overcomes the spring pressure in the ROUND HOLD OFF VALVE. Fluid flows into the line at the big nut , passed the piston seal, out the side fitting to the distribution valve, to the front brakes. Sometime watch the shaft move out as the brakes are applied by a helper.
If you wanted free flow through this valve it seems to me one would pull and hold the shaft open to unseat the piston seal.
Open to learning more if this sounds incorrect to others.

Mike

Okay, I see your point. So now I'm totally confused as to why it says in the manual....."The spring loaded end of the pressure metering valve must be depressed while bleeding. This can be done by depressing and holding the plunger in the end of the valve either by hand, or by clamping." Will doing that relieve the spring pressure somehow?? I've been trying to do this with a hand-held vacuum type bleeding tool which doesn't create enough vacuum (?) to overcome the spring pressure?? Some other instructions mention using a "pressure-type" bleeder. Not sure if that would make a difference or not?? I've ordered a new valve like I said and will let you know what I find. If it still doesn't work I'll have to find a "helper" to help me bleed the brakes the "old-fashioned" way by stepping on the brake pedal!! Thanks again for all your input Mike!!

[m22mike]

I have no comment on the directions in the service manual Joe.
Sorry I don't have any more
I can tell you. Maybe those that have had succes depressing the shaft during bleeding can explain what is happening in the valve.

Mike

['69Novajoe]

Hey Mike, I ended up buying a new metering valve (because I was convinced it was bad), pushed the plunger (which seemed to maybe move a little bit, if at all!!) and then proceeded to bleed the brakes. Actually, before I installed the valve, I checked it with my vacuum bleeder to see if it was allowing air through it and it was! Not sure if pushing that plunger did the trick or not!! I got good flow to the fronts now and the pedal has returned to the proper position and is rock hard!! Guess I got all of the air out of the system!! Everything seems to be working correctly at this point and I'm a happy camper!! Gonna go on a bit of a ride/cruise this Saturday to give it a good test. Thanks again for all your input and suggestions.

[mockingbird812]

Originally Posted by '69Novajoe

Hey Mike, I ended up buying a new metering valve (because I was convinced it was bad), pushed the plunger (which seemed to maybe move a little bit, if at all!!) and then proceeded to bleed the brakes. Actually, before I installed the valve, I checked it with my vacuum bleeder to see if it was allowing air through it and it was! Not sure if pushing that plunger did the trick or not!! I got good flow to the fronts now and the pedal has returned to the proper position and is rock hard!! Guess I got all of the air out of the system!! Everything seems to be working correctly at this point and I'm a happy camper!! Gonna go on a bit of a ride/cruise this Saturday to give it a good test. Thanks again for all your input and suggestions.

Glad to hear you got it working Joe. We may need to see a photo of your sweet ride!!

['69Novajoe]

Originally Posted by mockingbird812

Glad to hear you got it working Joe. We may need to see a photo of your sweet ride!!

Thanks Sam!! I'm actually going to be doing a bit of a "test drive" this coming Saturday to take some pics with another Nova that is scheduled to be shipped to the owner by the end of next week. I'll try to post some pics. In the meantime, here's a pic I took a little over a year ago. Boy how time flys!!

[mockingbird812]

Looks great Joe! Thanks!!!!!!