Front Brakes Don't Work - Need Help!

[Patcon]

I think for starters, I would pump the brakes a little slower. That allows the fluid to flow without as much vacuum on the system. I might also drop back to the tried and true bleeding method if possible and remove the variables of the speed bleeders

[Zed Head]

Left and right use the same chamber in the warning switch.  The pressure should equalize between left and right.  Hydraulics.

[Dens240]

I agree. I'm suspicious of the lines from the switch to the left caliper. I have made new hard lines today with no improvement. I've just ordered a replacement hose to see if that's the culprit. Interestingly, all hoses and lines were new. I should have just made my own lines from the start.

I replaced the speed bleeder with a standard bleeder and went to the old helper method with no improvement. Unless someone posts a eureka idea, I'll probably wait now until the new hose arrives late this week.

[Zed Head]

Blow some air through them.  

[Captain Obvious]

Dropping back a bunch just to be sure... Did you bench bleed the replacement master cylinder(s) when you put it on?

Also, you said you went to the old helper method of bleeding with no improvement. When you were underneath bleeding it old school, did you get a good stream of fluid out of the calipers when you cracked open the bleed nipple? Did that stream appear to be the same on both sides in the front?

[Dens240]

Cap'n - yes I bench bled the MC, which did improve things at that point. Prior to bench bleeding, I couldn't get fluid flow at either front caliper.

After many adjustments - bench bleeding the MC, double checking the spacing between the booster rod and the MC piston, adjusted the brake pedal travel to ensure the MC piston can run through its full range of motion, built and installed a new brake line between the MC front brake reservoir and the warning switch  - I was able to get a good full flow of fluid at the right caliper and I get good grip of the pads against the rotor.

However, I still only get a very low flow of fluid at the left caliper. It's like an old man with a swollen prostate. The video I posted was taken with the speed bleeders but it would look the same with the replacement bleed nipple and the helper method. I'm now working my way through the lines from the brake warning switch to the caliper to see if I can find an air leak.

[Patcon]

So the restriction could be anywhere from the switch to the caliper. You might want to disconnect lines until you find the restriction.

You could use air like Zed suggested, just dont blow brake fluid all over your paint. Get spills up quickly

[Captain Obvious]

Right.

If you're getting reasonable flow on one side an low flow on the other, then you shouldn't be looking for an air leak. You should be looking for a restriction somewhere between the caliper and the source. I would look carefully at the flexible line from the chassis to the caliper.

And I think your small leak at your pressure switch is something you need to address, but I don't think it's the cause of the big problem you're chasing.

[Zed Head]

Hydraulic principles say that if the system is connected correctly that you will get equal pressure on left and right.  It's not possible to have one side pressurized and the other not.  So, air leaks are not an option if the right side works correctly.

If you are getting fluid from both sides by pressing the pedal then what might be happening is that the piston is bound up in the caliper.  There's pressure but no movement.  Assuming that the hydraulic lines are correctly installed.  Or, there's a blockage inside the switch.  You might disconnect both lines at the switch and see if you get good flow from each port.

I sure hope that I don't start seeing a bunch of pharma ads about flow or stream...

p.s. I wrote this while others were posting.  But, "first principles" apply here, as far as problem solving.  The end of the warning switch has an inlet and two outlets, and hydraulics apply.  The only other variable might be time, but if somebody is sitting in the driver's seat with their foot on the pedal the fluid pressure will equilibrate.

Edited November 15, 2021 by Zed Head

[Dens240]

I did blow through the hard line from the switch to the hose but I haven't blown through the remainder. Also, I built a new line that goes from the switch to the hose and installed that as well with no improvement. I'm picking up a new hose tomorrow just in case and then when I get some time later in the week, I'll take the rest of that circuit apart. At least there was positive direction achieved today with the right caliper!

[Captain Obvious]

And by the way... what's the big picture history here? Is this something that just cropped up on a roadworthy car, or have you reached the "brake portion" of a long resurrection project?

[Captain Obvious]

2 minutes ago, Dens240 said:

I did blow through the hard line from the switch to the hose but I haven't blown through the remainder.

Yeah, I'd really take a real good look at that flexible hose. I don't remember if I've ever seen it specifically on a Z, but I've seen several cars where those flexible lines had closed down inside and restricted flow.