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I recently decided to bleed the brakes on my 1970 Cutlass Supreme conv. Rear brakes bled fine. I'm having trouble bleeding the fronts. No fluid comes out of the open bleeder. Currently, I have little-to-no pedal.
The factory shop manual mentions using a tool to depress the piston in the metering valve to get the discs to bleed properly. But the illustration in the FSM looks nothing like the metering valve that I have. At the rear of mine is a rubber cover. Beneath that cover is something pointy. When I try depressing that, it goes nowhere. What am I doing wrong ? The photo below shows my metering valve.
In over 45 years of working on these cars, I've never needed to press that button to bleed the brakes.
Check EVERYTHING. Have you verified that the holes in the bleeder screws are open and not plugged with rust? Have you verified that the outlet port in the wheel cylinder isn't plugged with rust or debris (I've seen that too)?
Assuming these are both good, start disassembling flare nuts until you find the spot that's dry.
Thanks for chiming in, Joe. With your expertise, I was hoping you'd see this thread.
It's possible that I wasn't opening the bleeder up enough to let the fluid thru. I was underneath the car, twisted up like a pretzel. Next try will be with the wheel removed. Should give me better access.
Is there any chance that it would be a problem with the distribution block ?
Thanks for chiming in, Joe. With your expertise, I was hoping you'd see this thread.
It's possible that I wasn't opening the bleeder up enough to let the fluid thru. I was underneath the car, twisted up like a pretzel. Next try will be with the wheel removed. Should give me better access.
Is there any chance that it would be a problem with the distribution block ?
Ron
It's certainly possible that there's a problem with the distribution block, but it is more likely that the problem is elsewhere. I'd completely remove the bleeder and ensure you can push a wire through the hole in the screw. With the bleeder out, brake fluid should run out of the wheel cylinder. If it does not, use a piece of copper or aluminum wire to poke in the hole where the bleeder screw goes to see if it is plugged with rust.
I haven't touched the distribution block yet. I want to follow Joe's advice first before touching the distribution block. Everything was working fine before I decided to bleed the brakes. It had been a while since they were last bled, even though the car is not driven more than 2or 3 thousand a year. I flushed out the lines. Then when I tried to bleed, this issue surfaced.
So if the distribution block is 'stuck', how do I unstick it ???
So if the distribution block is 'stuck', how do I unstick it ???
Ron
When this happens to me, I've been able to recenter the piston in the block by opening a bleeder on the other end of the system and pressing the pedal. This builds up pressure in the "stuck" side and usually moves the piston. If that doesn't work, there is rust or sludge in the block and you probably should replace it. It is possible to disassemble the block and replace the o-ring seals on the piston. Also, next time, get one of these tools that screws in place of the differential pressure switch contact and prevents the piston from moving all the way one way when you bleed the brakes.
The button under the rubber cover on pretty much any original metering valve is seized. (should be able to depress it)
As Joe said, never really been necessary to depress for bleeding brakes, but it will add to your problems if it seized.
But this only comes into play when trying to bleed the brakes. Right ? Otherwise, works fine in 'not depressed' mode for correct brake operation ?
OK. here's an update: I got tired of twisting myself up to get to the bleeder. So I removed the front wheels to give me easy access to the bleeder on the caliper. Also gave me a chance to try out my one-person brake bleeder. After proper setup, I opened the bleeder, then pumped the brakes. On both sides, I get a nice stream of fluid into the container. So possible reason for not getting any fluid initially is that the bleeder was not open sufficiently. I will continue this weekend. So if brakes are fully bled, how much travel should be in the pedal ? There seems to be excessive travel. But doesn't go to the floor.
And another update: Started the car and stepped on the brake. I had some pedal, but I also witnessed the distribution block performing its job. The brake light lit up, telling me that there was a serious pressure differential.
I know the fronts are good. So I removed the wheels in the rear and pulled off the drums. There was a puddle of brake fluid at the bottom of the RR backing plate. Looked like it had been leaking for a while. LR looked fine, BTW. New wheel cylinder to be picked up at NAPA tomorrow.
Regardless of pressing the button on the metering valve for bleeding, which does not seem to be necessary.
If the button is seized on the metering valve it denotes the valve is not working at all.
From my understanding of how the valve works, pressing the button defeats the front brake delay feature, allowing fluid to flow immediately, rather than being delayed for a fraction of a second. So if the button is not depressed, the delay feature is operational. Which is what you want all the time,except when bleeding.
The Button is spring loaded, when not pressed it will return to the out position.
The main point I am making is, most all originals have long since seized, rendering them useless.
The button seizes in the cast iron hosing. The fact that the button is seized proves nothing about the functioning (or lack thereof) of the actual valve.
June 16th, 2019, 10:11 AM
