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I'd gravity bleed without the proportioning valve tool. If you're having flow issues between the front and rear.. then power bleed it with Motive without the proportioning valve tool.
I'd gravity bleed without the proportioning valve tool. If you're having flow issues between the front and rear.. then power bleed it with Motive without the proportioning valve tool.
If the piston is truly stuck off-center in the Prop Valve, you will not be able to pressure bleed or gravity bleed.
The piston is designed to shut-off one half of the system. Either rears or fronts.
That little centering tool is handy, but it's for people that insist on using the Pedal Method for bleeding. Which works on all Chevys (except Vettes). LOL
You will not need the tool for pressure, gravity or vacuum methods of bleeding.
If you do wish to purchase the Motive Tank, look on EBay for a used one. Some people use them once, throw them in the corner of the garage.
I got one for a song. It just needed a new pump $12 and a new clear hose. Gauge was fine, tank was fine. Used ones will also need a thorough rinsing with denatured alcohol.
The lids for the master that comes with these Motives is a joke. Most of us pitch that in the round file box.
You can make a better lid for the master out of 1/2" Lexan. Then you can see inside the master as to what is happening during bleeding process.
<<<<<<<<<Click on my avatar <<<<< and search for photo albums, brake bleeding for some ideas.
If the piston is truly stuck off-center in the Prop Valve, you will not be able to pressure bleed or gravity bleed.
The piston is designed to shut-off one half of the system. Either rears or fronts.
That little centering tool is handy, but it's for people that insist on using the Pedal Method for bleeding. Which works on all Chevys (except Vettes). LOL
You will not need the tool for pressure, gravity or vacuum methods of bleeding.
If you do wish to purchase the Motive Tank, look on EBay for a used one. Some people use them once, throw them in the corner of the garage.
I got one for a song. It just needed a new pump $12 and a new clear hose. Used ones will also need a thorough rinsing of denatured alcohol.
The lids for the master that comes with these Motives is a joke. Most of us pitch that in the round file box.
You can make a better lid for the master out of 1/2" Lexan. Then you can see inside the master as to what is happening during bleeding process.
<<<<<<<<<Click on my avatar <<<<< and search for photo albums, brake bleeding for some ideas.
how would gravity bleeding trip the prop valve .. there is no pressure just asking
If the piston is truly stuck off-center in the Prop Valve, you will not be able to pressure bleed or gravity bleed.
The piston is designed to shut-off one half of the system. Either rears or fronts.
That little centering tool is handy, but it's for people that insist on using the Pedal Method for bleeding. Which works on all Chevys (except Vettes). LOL
You will not need the tool for pressure, gravity or vacuum methods of bleeding.
If you do wish to purchase the Motive Tank, look on EBay for a used one. Some people use them once, throw them in the corner of the garage.
I got one for a song. It just needed a new pump $12 and a new clear hose. Gauge was fine, tank was fine. Used ones will also need a thorough rinsing with denatured alcohol.
The lids for the master that comes with these Motives is a joke. Most of us pitch that in the round file box.
You can make a better lid for the master out of 1/2" Lexan. Then you can see inside the master as to what is happening during bleeding process.
<<<<<<<<<Click on my avatar <<<<< and search for photo albums, brake bleeding for some ideas.
Thank you!
I already have a Motive bleeder that I use with my C7, what I need to buy is the adapter for the C3 master cylinder.
The issue is that my car can be purged in the traditional way without problems, there is no line through which liquid does not come out, hence my confusion.
I bought the tank and adapter plate for $90. The tank is useless though. You're suppose to fill the tank with brake fluid but no one likes cleaning it out when you're done. Plus it takes 15 - 20 pumps per 5 lbs... which leaves you exhausted.
I recommend the adapter plate $45. Get a Amazon Basic air hose coupler set for $20. Or grab em from Harbor Freight. Hook up the adapter to your air compressor. Set it at 10 PSI, Motive says you can go as high as 15 PSI. Top off both front/rear reservoir with brake fluid. Put the adapter on top of the master cylinder and lock it down snug with 2 C clamps. Start bleeding the passenger side (furtherest away). Typical after 30 seconds you have to remove the adapter and refill the master cylinder.
What I LOVE about the adapter plate.... the ability to troubleshoot. A spray bottle of warm water mixed dish soap will help you find small leaks. In areas where you can't see soap bubbles (inside the calipers) you can listen for leaks.
Realistically, I can bleed the brakes in 15 minutes. I'll spend way more time jacking the car up, removing wheels and looking for tools.
I bought the tank and adapter plate for $90. The tank is useless though. You're suppose to fill the tank with brake fluid but no one likes cleaning it out when you're done. Plus it takes 15 - 20 pumps per 5 lbs... which leaves you exhausted.
I recommend the adapter plate $45. Get a Amazon Basic air hose coupler set for $20. Or grab em from Harbor Freight. Hook up the adapter to your air compressor. Set it at 10 PSI, Motive says you can go as high as 15 PSI. Top off both front/rear reservoir with brake fluid. Put the adapter on top of the master cylinder and lock it down snug with 2 C clamps. Start bleeding the passenger side (furtherest away). Typical after 30 seconds you have to remove the adapter and refill the master cylinder.
What I LOVE about the adapter plate.... the ability to troubleshoot. A spray bottle of warm water mixed dish soap will help you find small leaks. In areas where you can't see soap bubbles (inside the calipers) you can listen for leaks.
Realistically, I can bleed the brakes in 15 minutes. I'll spend way more time jacking the car up, removing wheels and looking for tools.
pifo1964
If you don't want to wait for the motive pressure bleeder you can make a pressure bleeder out of a garden sprayer, some tygon tubing, some hardware store fittings, clamps, a pressure gauge and an aluminum plate..... and clamp it on using a big-*** c-clamp.
I made mine ages ago and I figured I'd buy the real pressure bleeder later....but it has worked so well that I never bought a real one. I made myself a rubber gasket out of an inner tube and it seals very well (no leaks). My aluminum plate is "gouged" on the underside so that both sides pressurize..... and YES I put the brake fluid in the garden sprayer with and just pump it up between 10 psig to 20 psig and bleed....... pump it up again when it gets down the 10 psig.
I'll see if I can find the link somebody posted here....
I'm not very handy with electrical problems, but I don't think the problem is the parking brake, as when I unplug the connector with the brown wire from the valve, the dash light goes off. And when I put the handbrake on, it doesn't turn on.
No, you don't fill the tank with DOT3. What does that tank hold, two gallons?
You only need a couple of large bottles of DOT3 in the tank. The rest is air. And just a few pumps brings the pressure up to 10 - 12 lbs. You don't need a lot to flush brake lines.
The whole idea of having DOT3 in the tank is so you can easily have enough fluid to do all six bleeders and then some.
And without constantly removing the lid to peek inside the master. Hence, the master will never run dry using two lg bottles.
You can make a clear master lid for less than $30. Easy-peevy.
Good points. No need to "fill" the pressurized tank, I typically add a couple of large bottles. Fixed my post too....
Originally Posted by HeadsU.P.
Motive Tank,
No, you don't fill the tank with DOT3. What does that tank hold, two gallons?
You only need a couple of large bottles of DOT3 in the tank. The rest is air. And just a few pumps brings the pressure up to 10 - 12 lbs. You don't need a lot to flush brake lines.
The whole idea of having DOT3 in the tank is so you can easily have enough fluid to do all six bleeders and then some.
And without constantly removing the lid to peek inside the master. Hence, the master will never run dry using two lg bottles.
You can make a clear master lid for less than $30. Easy-peevy.
We have gotten a little off-topic from the OPs light being on.
I find it very curious that your light is on, (meaning your shuttle valve is tripped), and yet you have fluid flow to all 4 wheels.
I think you may still have less flow than you realize. You may have reduced braking power. And it would be wise to fix this.
The diagram in post #12 is a GM diagram for your brass block. It is really simple, there is only one moving part.
You can remove the plastic switch in the center, no fluid will leak out.
The contact tip of the switch needs to touch the shuttle to turn on the light. You could test the wiring by grounding that wire lead or switch contact to a random screw on the frame.
However when it turns on the light, flow should be stopped to one end of the car.
Regardless once the switch is removed, you can look inside, and see the shuttle valve.
By looking at the diagram you can tell if it is centered or not.
You should not see a "shoulder".
You can move the shuttle valve with an o-ring pic or a small screwdriver.
That is what I had to do to fix a customer car.
But mine was on the bench.
In your case I would inspect and see if there is anything else in there, causing contact.
Once it is centered, the tool will hold it there, but the tool will not move it.
Last edited by leigh1322; Dec 24, 2024 at 11:38 PM.
We have gotten a little off-topic from the OPs light being on.
I find it very curious that your light is on, (meaning your shuttle valve is tripped), and yet you have fluid flow to all 4 wheels.
I think you may still have less flow than you realize. You may have reduced braking power. And it would be wise to fix this.
The diagram in post #12 is a GM diagram for your brass block. It is really simple, there is only one moving part.
You can remove the plastic switch in the center, no fluid will leak out.
The contact tip of the switch needs to touch the shuttle to turn on the light. You could test the wiring by grounding that wire lead or switch contact to a random screw on the frame.
However when it turns on the light, flow should be stopped to one end of the car.
Regardless once the switch is removed, you can look inside, and see the shuttle valve.
By looking at the diagram you can tell if it is centered or not.
You should not see a "shoulder".
You can move the shuttle valve with an o-ring pic or a small screwdriver.
That is what I had to do to fix a customer car.
But mine was on the bench.
In your case I would inspect and see if there is anything else in there, causing contact.
Once it is centered, the tool will hold it there, but the tool will not move it.
I agree, if it's tripped gravity bleeding will be ineffective. It will be like trying to milk a bull. You'll have disproportionate amount of brake fluid bleeding between the front and rear.
Why not just power bleed it. When you're done, stab the brake pedal 3 times and it should reset your valve. It worked for me.
Resetting the valve on your bench now adds two hours of labor to job. You don't know if the previous installer stripped any of the fittings. You risk cross threading or stripping the fittings. If you damage any fittings, you can not simply reflare the line because they all have tight 90' bends that won't fit in a flare tool. Now you've got to replace the whole line. God forbide you damage the front passenger side line, now you've got to loosen up your Boregenson power steering pump hardware to get a new brake line pass it. Why risk it? Avoid it at all cost.
glad to see so many other thoughts on this issue... it's confusing, misunderstood and many different ways to approach it
Thanks!!
It also surprises me that if the valve is blocking, the flow of brake fluid would come out through the 4 bleeders. Maybe it's as you say and the flow towards one of the sides is less and when bleeding I don't notice it.
As I mentioned, apparently the car brakes evenly and does not have strange tendencies if I brake suddenly. I did a road test braking often, stopped the car and very carefully touched the discs, the four were very hot. Obviously this does not indicate whether there is one side that brakes noticeably more than the other, but it does indicate that the 4 wheels have brake.
With your advices I have a work to do, thanks again!
so, there's distribution blocks, as depicted in the nice picture on p.1 of this thread, and then there's Proportioning Valves.
how do you reset a PV? same? stab brake pedal really hard multiple times? crack open one of the bleeders on the opposite end of the car that caused it to trip, and press the brake pedal?
if the brake light is OFF, does that mean the PV is centered and GTG? assuming the electrical circuit is functional and not "broken".
If the brake light is off, you are GTG, providing the circuit works.
To test the circuit, remove the wire from the plastic switch at the distribution block, and ground the wire. The brake light will come on if the circuit is good.
Then, if it is plugged in, and the light is off, then you know the shuttle valve is centered.
It can be centered with a awl, o-ring pick, in the car. But stabbing the brake pedal hard, and slipping your foot off, a couple times, is much easier.
so, there's distribution blocks, as depicted in the nice picture on p.1 of this thread, and then there's Proportioning Valves.
how do you reset a PV? same? stab brake pedal really hard multiple times? crack open one of the bleeders on the opposite end of the car that caused it to trip, and press the brake pedal?
if the brake light is OFF, does that mean the PV is centered and GTG? assuming the electrical circuit is functional and not "broken".
Call it what you want... distribution block, proportioning valve, brake light switch.... its all those things in one. Follow the two metal lines leaving the master cylinder to the PV. There is only one though.
Your front and rear brakes are 100% completely separate systems. Its designed this way to get you home safely should one fail. Front/rear lines go into the same PV but don't actually mix. As long as you have equal pressure, the piston is centered, no brake light. If a leak develop, pressure is lost and the piston slides... and trips the brake light.
I had a bad Master Cylinder causing my rear brakes to lock up when shifting out of park or during rapid braking. Stabbing the brake pedal worked some times. One time, after 30 minutes of being stuck on the highway, i just cut my rear brake hose and drove home. The last time it happened, i was able to walk to an AutoZone and buy a wrench and relieve the pressure on the brake hose. My case was extreme. The PV is like your carb.... it gets blamed for everything. You gotta look past it and see what's causing it to trip.
Proportioning is already built into the brake system by the sizing of the caliper pistons to get the right balance (proportion) of braking force between front and back.
I know Summit sells adjustable PV for other hotrods. You can dial in the front/rear brakes. The whole purpose of the the PV is to keep the rear end from coming around under heavy braking. I wasn't aware that our calipers were designed to take that into account. Its almost like its not a proportioning valve at all really. Engineers can use line diameter to "porportion". What about the fact that the front gets two dedicated lines but the rear only gets one split line?
