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Brake pedal pushes back??????

Been drunk/hungover last couple days. I will do the test Fordum when I get back from work.

Also, the pedal is physically pushing my foot up when I turn off the truck. I cannot fight it. Happens every time I turn it off.
 
Forgot I don't have an open top MC. :( I might be able to see a gush of fluid when letting off the brake, but not by myself.

I've been looking at separate prop valves. Considering this is off a 1500 Burb, I might try a 3500 truck prop valve. The calipers and pistons are going to be bigger, so it might be a better choice.

 
I'm running a corvette mc, with a wildwood disc/disc prop valve I got on summit. It was the best setup I have had and just locks up my 37s when I push it to the floor. I still have a lot of trouble with that.
I think there also is something to do with the pivot pin and how the linkage works with the pedal. The hydro boost has a different setup and may give more braking with less pedal travel due to this. Id like to investigate and find a solution too. In the mean time, this setup holds me at any angle in 4low.
 
sizing of the bore is important to run the big brakes....the one ton stuff is much bigger than the other stuff, and the disc calipers on the back require more fluid as well...I run a 1-5/16" bore m/c from a 78C30, made a custom length pushrod,...and a hydro boost system from a diesel K5. I use an adjustable prop valve for the rear, got rid of the factory prop valve and my system works great on my 39.5 equipped rig.
 
Does anyone have a K30 parts truck they can pull the prop valve off? Rockauto doesn't seem to have the prop valve and can't find it on eBay. Unless maybe I had a part number for it.
 
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Haven't found anything yet. I know there is one around here someplace though.... unless someone took it when they were here picking up other parts.
 
FWIW, I finally remembered to try it, and my brake pedal stays right where it is when I turn off the engine.
Of course, mine is a Ford, but the basic idea is identical.
 
I've been reluctantly going to work these past couple days lol, so no updates. I did purchase the older k30 master and booster Chris was talking about. Figured at least change the booster since it's probably original. Now I'm hoping to hit up a local junkyard in search of a C/K30 prop valve. I think that will help complete the change to a K30 setup.

Chris and I will be tackling this tomorrow if everything goes right in the the Universe :D
 
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did you block off vac to the booster? did that change the kickback?
 
readymix said:
You bought a booster? I offered one to you for free... return that thing and take mine.
Click to expand...

Sorry B, I don't know how I missed that. I know you were looking for a prop valve for me, but didn't read about the other stuff. But, right now, since Chris is coming down tomorrow morning, I'll just use it. Doesn't much matter right now, just need it working. Also, it's probably worth it, not having to drive ways the heck out to you :doah::haha: I was picking up materials for work and swung by my local junkyard just to run through. It has a couple K20s and one C30 duallie waiting to go in. I might pull the prop valve off the C30 tomorrow with Chris real quick if they let me before it's in the yard. :dunno:
 
Completely confused
The beer has come out. Chris and I are done for today. We have no idea what's going on but the "pedal pushing back" was the check valve on the vac line. Everything else is still terrible :(

image.jpg
 
Just saw this. Hope you get it figured out. I'm sure you will. You better! Hell, put the factory stuff back on!



Anyways, glad Chris tried to help. Cool guy! Met him one time to buy my shackle flip. Needed more time with him but he was working and I had my family with me. Good times!



Get r done!! You can do it!



Sorry I'm no help.
 
First thing we did was swap out the vacuum booster check valve. That helped the goofy push back on the pedal. Then Chris jumped in, started it, and proceeded to power through the brakes on dirt in 2WD.

Jacked up the truck and put jack stands under it. Put it in 4L, 4H, 2H and played with the brakes. It took 80% of the pedal travel to stop the wheels from spinning, in the air. Only took letting off a small amount before they spun again. In any gear, it would power through the brakes like nothing.

Then we ditched the 2005 Suburban MC and prop valve.

Put in a 1 5/16 1985 K30 master cylinder. Running straight line, no prop valve. We bled the MC for 15-20 minutes, just pumping and pumping until all the air was out. Then bled all the calipers, again taking lots of time to make sure the air was out. All corners bled fine, free flowing, clean. Then sanded down the rotors because they were a bit glazed.

Started the truck and again performed the same tests. No difference, at all. While it was idling in DRIVE and 4L, Chris tries to turn the tires by hand while I hold the brake. Unless I have my full force on the pedal.....he is able to rotate the tires.

The pedal doesn't feel spongy so much as it just feels weak. It is easy to push in, then abruptly ends. It is so easy to push in, I can do it by hand and bottom out the pedal. It does not build enough pressure before it ends, that's for sure. During bleeding, the pedal will hit the floor, but will not while it's running. Even pulled the vacuum off the booster while it was running, just for shiggles, and tried to stop the tires from spinning. It would again power through the brakes easily, like under 1000 RPM easily.

So the celebratory beers came out. Obviously it wasn't a success, but at least now there was someone else going crazy and not just me. Funny, Chris thought I was exaggerating the problem when he arrived. Didn't seem like he wanted to test drive the truck afterwords. Yeah, I know, but I've put 3,000 miles on it like this. :doah::haha:

*needs crying smilie

EDIT: forgot to mention, the new K30 booster I got is exactly like the one I already had on the truck. The rods were the same and exterior balloon size was the same too. Doesn't seem to be a booster issue anyway.
 
Couple things...

Have you read this?

http://www.pirate4x4.com/tech/billavista/Brakes/

Where are you getting your master cylinders? Are they new?

When you hold the pedal and maintain pressure does it stay, or does it fade?

If you pump the pedal does the pedal travel decrease?

You can adapt a pressure gage on to the master and confirm pressure. This will split the system for troubleshooting- that's what I would do if it were mine, as a starting point.

One other thought- flex lines, are they good?
 
What calipers are you running in the rear? Everything you're describing is saying that you have air in the lines (or too much flexible line that can expand and reduce your pressure).

Are you sure you've got the correct line from the master cylinder going to the front/rear? I know on my S-10 it's backwards which had my brakes all screwed up until I figured it out (front brakes are rear connection, rear brakes are front connection).

I'll be honest, I've never had a good feeling pedal on a rig that didn't have factory brakes, but I have made them all stop properly. On my 72 blazer I have a similar setup to you, Dodge D60 up front with disk brake conversion on a 14 bolt (3/4 ton front calipers IIRC). I am running a K30 same vintage master cylinder with the stock vacuum booster and an adjustable proportioning valve with a manual line lock and cutting brakes on the rear. My pedal is soft, but it will stop the truck.

The trick to getting it to stop was good pads, I run Porterfield R4S pads, but I have heard that the EBC Yellow pads are good too. But from reading your last post you have bigger problems then brake pads.
 
FWP said:
Couple things...

Have you read this?
Am about to..

http://www.pirate4x4.com/tech/billavista/Brakes/

Where are you getting your master cylinders? Are they new?
All of them were new except the 2005 MC.

When you hold the pedal and maintain pressure does it stay, or does it fade?
Stay

If you pump the pedal does the pedal travel decrease?
No, it stays the same. Only if the engine is off will it pump up.

You can adapt a pressure gage on to the master and confirm pressure. This will split the system for troubleshooting- that's what I would do if it were mine, as a starting point.
We thought that's what we were doing. It wont hold in 2H, off the ground. It rolls through the front brakes in 2H while on the ground. It rolls through the brakes in 4H/L easily while off the ground. I'll see if I can find a gauge and connect it to the bleeders.

One other thought- flex lines, are they good?
All drops are braided lines from ORD and are in good shape. The small ~12" rubber lines at the rear calipers are also in good shape. All braking components (outside the master and hardlines) have ~3,000 miles
Click to expand...

Red
Gunna check out that link right now
 
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