y5mgisi
1 ton status
Or I could see a case for the booster being bad and it sort of "giving up" on assisting after a certain amount of resistance.
CK5
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Brake pedal pushes back??????
- Thread starter K85 Octane
- Start date
I can't see the booster being bad but at this point why the f*** not replace it. Problem is, if the booster was bad, the pedal would be hard. I don't think there's any other way it could be bad.
Just pulled the booster off. Looks exactly like the K30 booster I bought. Seems to be working fine too. I'll set it aside for now and throw the new one on. Make a run to Oreilly's and Home Depot to grab some stuff.
Also, if there is a massive air bubble in the rear lines, wouldn't the fronts still work? And Vise verse? Just seems like it to me but I haven't a clue lol
Kind of thought you would have already caught that.
I had a Toyota this happened on. He bought one of those bleeders where you put fluid in at the bleeder. We tried everything with his. Even had to do this twice with the reverse bleeder.
Nothing odd or unusual about the truck. Built it exactly like several others I had built.
Also we aren't tired of helping shoot if I were any reasonable distance away I would be over helping
y5mgisi
1 ton status
I'm just wondering if maybe there is a leak internally to the booster that only shows itself while the diaphragm is in a position other than at rest. Also, I have seen them with broken Springs internally but don't know if that would cause your issue.
I'm not really saying that I think the booster is your issue, cause I too think it's either good or bad and not somewhere in the middle, but I can imagine a scenario where something is wrong with it.
I'm not really saying that I think the booster is your issue, cause I too think it's either good or bad and not somewhere in the middle, but I can imagine a scenario where something is wrong with it.
Installing booster now.
Before I start bleeding the brakes again (I am alone, so it's only going to be gravity bleed) should I reconnect the stock K5 prop valve? Or should I leave it completely bypassed?
Before I start bleeding the brakes again (I am alone, so it's only going to be gravity bleed) should I reconnect the stock K5 prop valve? Or should I leave it completely bypassed?
I would hoom it up or leave bypassed depending on how you want to run them. Mine is hooked up.
You can pressure bleed by yourself. Put a hose on the bleeder that goes into a container full of brake fluid. You just need to make sure the hose end is submerged in brake fluid and have enough in there to allow you to pump several times. I put the container on the ground.
Done this several times works good
You can pressure bleed by yourself. Put a hose on the bleeder that goes into a container full of brake fluid. You just need to make sure the hose end is submerged in brake fluid and have enough in there to allow you to pump several times. I put the container on the ground.
Done this several times works good
y5mgisi
1 ton status
Me too on the tube/bottle method. Just gotta keep a close eye on fluid level cause it bleeds out pretty fast.
At some point, someone already removed the factory prop valve from the frame 
I no longer have one. All this time I thought it was just sitting there. I wonder who pulled it hmmm
I no longer have one. All this time I thought it was just sitting there. I wonder who pulled it hmmm
Interesting. I wonder which way is better.
If I gravity bleed them, I can walk around and watch for bubbles, or weird stuff. If I "bucket full, hose in, pressure bleed" them....I can't really see much of anything. Just pump the pedal a crap ton of times (being careful not to run the master dry) and call it good?
Bypass lines
I don't want to say to throw parts at it, BUT at this point I would grab a cheap set of non metalic front pads an put them on.
You've had multiple masters all with the same "too much travel issue" so for the sake of this arguement lets say the master is not the issue.
Next there is no more valves between the master and the caliper except for a 2 psi residual pressure on the front (verified to be in the correct direction).
All hoses are in new condition and no longer than necessary.
Its been vacuum bled, pressure bled, gravity bled, and bled traditionally, by multiple people, so again, probably not air in the lines.
The vacuum booster makes the pedal able to be pressed almost all the way floor, so it's working.
Rotors have been cross sanded with fairly rough sand paper to verify that there's no glazing. I think pads are the only constant here. A cheap set of pads are like 20-25 bucks and easy to install. Just my 2cents
You've had multiple masters all with the same "too much travel issue" so for the sake of this arguement lets say the master is not the issue.
Next there is no more valves between the master and the caliper except for a 2 psi residual pressure on the front (verified to be in the correct direction).
All hoses are in new condition and no longer than necessary.
Its been vacuum bled, pressure bled, gravity bled, and bled traditionally, by multiple people, so again, probably not air in the lines.
The vacuum booster makes the pedal able to be pressed almost all the way floor, so it's working.
Rotors have been cross sanded with fairly rough sand paper to verify that there's no glazing. I think pads are the only constant here. A cheap set of pads are like 20-25 bucks and easy to install. Just my 2cents
y5mgisi
1 ton status
Well you just sorta contradicted yourself. Noair in the llines, plus good master, yet can push almost to the floor? Push to the floor means a bad master or air. The pads don't compress am appreciable amount. Air does compress. So if the issue is that the pedal goes to the floor, there is a problem.
Driver side pads with ~3,000 miles. Inner D60 and rear inner 1/2 ton. They are both a little shiny and ultra smooth, light is just hitting one differently. I don't know why glazed pads would make a spongy pedal.
I had a problem vehicle like this at work recently and had to end up calling gm tech assistance. First of all the rubber lines on the back calipers need to be looped down or remove the calipers and let them hang with a block of wood in them. They told me a different way to bleed air out. Engine off have a helper push the pedal down SLOW once and hold. Then you crack the bleeder quick and get your shot of fluid and/or air and close it right back up. Then the helper can SLOWLY let up on the pedal. Next they told me to wait 15 seconds and then do it again, that is supposedly the key. Do that at one wheel until the master needs refilled, and then go to the next wheel. Of course in the normal order RR, LR, RF, and LF.
I can push the pedal almost all the way to the floor on any power brake system I've ever driven. There will always be some expansion of the soft lines and with enough pressure you can get the pedal down. On Brent's truck it takes force to push the pedal down that far, not happening with a hand. With the truck off and no power boost can only push it down 3" or so using both feet.
or drive it. will the fronts lock up?
No prop valve would be a concern to look at for me. Especially with nothing in its place.
Shinny pads don't make a spongy pedal.
The front gets 60% back gets 40% or so. Your sending 50/50 is the master designed to do that?
Shinny pads don't make a spongy pedal.
The front gets 60% back gets 40% or so. Your sending 50/50 is the master designed to do that?
y5mgisi
1 ton status
Gotcha. I feel like we might be dealing with two separate issues. I kinda suspect that from the start the rears weren't doing much which caused the fronts to do all the work to cause the glazed pads. I also think maybe the pads aren't the best match for the truck. Maybe those pads have a specific break I procedure. Then I still feel like there could possibly be air somewhere.
I am guessing that the fronts are bigger then the rears? Mine are, but my front are Ford calipers. In theory then the front should be getting more fluid.
With out a prop valve you are sending the same to both.
With out a prop valve you are sending the same to both.
