Brake issues

[nhtc33d]

I am have a issue with soft pedal in my project. Replaced entire brake system except for rear brake hose. New disc/drum setup with manual m/c with prop valve. Bench bled m/c, gravity bled system 2x did the pump and hold 2x went through 3 bottles of fluid but still have soft pedal. BUT if i pump it up quicky and dont release the brake pedal completely it stays firm. Just keeping the pedal pushed down 1/4 inch keeps the brakes up. Could there still be air in the lines or do you think there is other problems?

[Fred T]

A couple of possibilities.

Check the rear hose. Does it expand when pressure is applied?

Check all connections for leaks.

When bleeding, I use a clear hose and bottle. Loop the hose so it is above the brake cylinder or caliper. When the pedal is depressed, you should not have any bubbles in the fluid in the hose. If their are and only on one wheel, there is a leak at a fitting for that wheel. If there are bubbles at all wheels, the problem is with the master cylinder. If bubbles at only front or rears, a leak between the m/c and the tee for that set.

[nhtc33d]

Originally Posted by Fred T

A couple of possibilities.

Check the rear hose. Does it expand when pressure is applied?

Check all connections for leaks.

When bleeding, I use a clear hose and bottle. Loop the hose so it is above the brake cylinder or caliper. When the pedal is depressed, you should not have any bubbles in the fluid in the hose. If their are and only on one wheel, there is a leak at a fitting for that wheel. If there are bubbles at all wheels, the problem is with the master cylinder. If bubbles at only front or rears, a leak between the m/c and the tee for that set.

Thanks for the reply,
I went ahead and replaced the hose just in case it was a issue. Still soft pedal. I removed the lines coming out of the m/c and plugged them to do a pressure test on m/c and its fine. I am using the clear hose /bottle but i am not looping the hose above the wheel i am bleeding so i will try that. When i am bleeding i do not see any air bubbles and I do not see any leaks anywhere? Very frustraing!! I think i will clamp off the rubber hoses and try to isolate the problem area ie.front/back. If you have any other ideas let em rip!! thanks again

[raycow]

Sorry to ask the obvious, but nobody else did. Are the calipers installed so the bleeder screws are at the very top? They do have a left and right. Some rear wheel cylinders also have a left and right but it is harder to install those upside down.

Ray

[nhtc33d]

Originally Posted by raycow

Sorry to ask the obvious, but nobody else did. Are the calipers installed so the bleeder screws are at the very top? They do have a left and right. Some rear wheel cylinders also have a left and right but it is harder to install those upside down.

Ray

Thanks for the reply, They are pointing up but not completely at 12:00. I did remove them and turn them as i was bleeding the system to ensure all air was out of them. It really feels like air is still in the system but after bellding so many times i find it inprobable but not impossible! Thanks again!!

[datguysaL]

could be the metering valve, you sometimes have to push or pull the pin when bleeding the brakes. air is probly being held back by it.

[87chevy.com]

So, this project truck, does it feel soft compared to before you started messing with the brakes? Was it power brakes before you messed with it? whats your project? are you comparing the pedal of yours to something else? if you have all of the air out, maybe your M/C is incorrectly sized to the application.
clint

[nhtc33d]

Originally Posted by datguysaL

could be the metering valve, you sometimes have to push or pull the pin when bleeding the brakes. air is probly being held back by it.

Checked this and it is set in the correct position.

Originally Posted by 87chevy.com

So, this project truck, does it feel soft compared to before you started messing with the brakes? Was it power brakes before you messed with it? whats your project? are you comparing the pedal of yours to something else? if you have all of the air out, maybe your M/C is incorrectly sized to the application.
clint

When i got the truck it was in boxes so i really dont know how they were before i got it. As for the comparision i really dont have any thing except power brakes but they are really soft and go to the floor.
I bought a m/c kit from Performance online specifically for my setup so that should be ok too.
I pinched off all the rubber lines and opened 1 at a time and it appears the problem is in the front brakes. When i pinch off both front lines and leave the back open the pedal is high and hard. pinch off rear and pedal is low and soft. I dont know where to go from here. Thanks again for all the suggestions
Mark

[SCOTI]

Explain your bleeding procedure (how do you manipulate the pedal; what are you bleeding 1st, 2nd, 3rd, 4th; etc). Maybe it's something there??

[nhtc33d]

[QUOTE=SCOTI;4013060]Explain your bleeding procedure (how do you manipulate the pedal; what are you bleeding 1st, 2nd, 3rd, 4th; etc). Maybe it's something there??[/QUOTE

Thanks for the reply,

For both gravity and the "pump,hold,bleed" method i start from the p/s rear, d/s rear, p/s front, d/s front. I use a length of clear tubing into a clear bottle
1/2 full of new fluid. The hose is submerged into the fluid.
For the gravity method I just open a bleeder and let run until the m/c is 1/2 to 3/4 empty and repeat pn all wheels.
The other method we pump brakes until they start to feel firm, hold pedal, open bleeder until the pedal goes almost to the floor. lather,rinse,repeat!
Does this sound ok? I have a feeling the problem is something really simple or really stupid (probably both!) that i messed up!

[SCOTI]

Originally Posted by nhtc33d

Thanks for the reply,

For both gravity and the "pump,hold,bleed" method i start from the p/s rear, d/s rear, p/s front, d/s front. I use a length of clear tubing into a clear bottle
1/2 full of new fluid. The hose is submerged into the fluid.
For the gravity method I just open a bleeder and let run until the m/c is 1/2 to 3/4 empty and repeat pn all wheels.
The other method we pump brakes until they start to feel firm, hold pedal, open bleeder until the pedal goes almost to the floor. lather,rinse,repeat!
Does this sound ok? I have a feeling the problem is something really simple or really stupid (probably both!) that i messed up!

I do the 2-person pump, hold, & bleed method. I've run into the same issue on a few occassions. When that happens, I change the technique slightly.

Try starting w/o pressure on the pedal. Leave the pedal unpressed. Open the bleeder screw & then slowly (not slow-motion, but not panic stop either) depress the pedal until it bottoms out. Hold the pedal bottomed out until the bleeder screw is closed. Release the pedal slowly. Repeat.

I do this x3 @ each corner (farthest from master cylinder to closest like you're doing). It seems to help the prop valve 'sticking' issues.
See if that does anything for the issue.....

[nhtc33d]

Originally Posted by SCOTI

I do the 2-person pump, hold, & bleed method. I've run into the same issue on a few occassions. When that happens, I change the technique slightly.

Try starting w/o pressure on the pedal. Leave the pedal unpressed. Open the bleeder screw & then slowly (not slow-motion, but not panic stop either) depress the pedal until it bottoms out. Hold the pedal bottomed out until the bleeder screw is closed. Release the pedal slowly. Repeat.

I do this x3 @ each corner (farthest from master cylinder to closest like you're doing). It seems to help the prop valve 'sticking' issues.
See if that does anything for the issue.....

Thanks for the tip! I hope to have some time this weekend to chip away at it again so i'll let you know how i make out!

[nhtc33d]

Well, I worked on the brakes again and now i have a semi firm pedal about 1/2 way through the distance of the pedal but if i push really hard i can get it to the floor. I also noticed that the front pads move way before the rear shoes start to move. could this be an issue with the residual valve? I called the place where i bought the kit and they said no. Any ideas?

[Mike J]

i just redid all of my brake system and upgraded to front disks and power brakes while i was at it and I was having a little trouble getting mine to bleed as well. I dont know if you said this but make sure you bleed between the master and proportioning valve- I had some air there

[cdowns]

when you bleed the rears you should bleed the furhest away first which is the drivers side then the passenger side second
also the rear brake shoes should b out very close to the drums,less than a thousandths of inch

thats the way to do it on the 67-72chevy trucks which is a guess since no brand or year was mentioned

[nhtc33d]

Originally Posted by cdowns

when you bleed the rears you should bleed the furhest away first which is the drivers side then the passenger side second
also the rear brake shoes should b out very close to the drums,less than a thousandths of inch

thats the way to do it on the 67-72chevy trucks which is a guess since no brand or year was mentioned

Thats the way i have been bleeding also. I set the rear shoes to the point where if i put the wheel on it will spin 1 rotation before stopping.
As many times as ibleeded the brakes i cant think there is still air in the lines but i might break down and buy a pressure bleeder to be sure. I still think its odd that the front brakes react way before the rears????

[raycow]

Originally Posted by nhtc33d

I still think its odd that the front brakes react way before the rears????

That's the proportioning valve behaving normally. It is designed not to send fluid to the rears until the fronts have reached a predetermined pressure.

Ray

[nhtc33d]

Originally Posted by raycow

That's the proportioning valve behaving normally. It is designed not to send fluid to the rears until the fronts have reached a predetermined pressure.

Ray

Thanks for the reply. Glad to hear thats a normal issue. I still need to figure out why i dont get any real pedal until about 1/2 way through the brake pedal stroke? Any ideas on that?