cant get front brakes to work

[del0075]

i have been a member a for a while, just kinda looking around at the builds and old trucks. but now i have a ????. and was wondering if somebody can give me some helpful advice of what to look for or do....... this is what i have..... 1971 gmc 3/4 ton 4x4, i installed a new 383 stroker in it, while i was doing it i decided to rebuild the front end and put new brakes on it. it has been setting for about 12 years, i have put new power booster, new calipers, new master cylinder, new proportion valve, and new rear wheel cylinders. i have really good back brakes, but i have no front brakes, i have also replaced the new master cylinder, and front brake pads, thinking that may be it. i have never had this problem before, and i am now baffled, any ideas would be much appreciated.....

[BERT306]

When you bleed the front are you getting any fluid movement

[BigSwid79]

I've heard of the problem you are having before. Its hard to explain whats really going on but it seems like a proportioning valve problem but if your getting fluid to the brakes you wouldn't suspect it to be that. If you replaced all your front lines your prop valve could be reacting as if you lost your front brakes and to compensate for it, it has to get your back brakes more fluid. Even though a little fluid is getting to the front brakes still all the fluid pressure is getting to your back brakes and its not allowing your front ones to work properly. I had the same problem with my truck except my front brakes were good and I had no back brakes. All I did was drive my truck around my field and pound on the brake pedal a couple times and it eventually evened back. This is just kind of my theory I may be way off but it worked for me

Hopes this help, Swid

[del0075]

i get fluid out of the bleeder valve, its a good full stream, the only thing i have not replaced is the brake line itself.........

[BigSwid79]

Ohh man I don't know then. I hope you figure something out Good luck
Swid

[BERT306]

Might be a dumb question but.... is your bleeder valves on TOP of the calipers in relation to where your brake hose bolts on? if your bleeder is on bottom or below your brake line you will not get air out and caliper wont work.

[del0075]

the bleeder valves can only be on top...........

[SeventyOne]

You bled from rear passenger, rear driver, front pass, to front driver - in that order?

[rayfinseats]

If all else fails try bleeding from the brake line on the master cyl since it is the highest point in the system and that is where the air will end up.

[SeventyOne]

Did you bench bleed the master?

[BERT306]

Originally Posted by del0075

the bleeder valves can only be on top...........

well havnt paid attention to my truck but on my old chevelle i had put the calipers on the wrong side and bleeders were down, Plenty of fluid when bleeding but still didn't have brakes. Calipers would swap from right to left on the car

[del0075]

yeah i have bled them pas rear, dr rear pas fr, dr front. just replace front calipers to see if they was the problem, didnt change any thing. on the truck the calipers can only go on one side they are not able to be switched ........




i am starting to wonder if the metal brake lines can be plugged.........

[72lb4x4]

I always run the MC dry when I try to bleed the brakes and hate to ask for help so I fix everything and then just take the vehicle to the place up the street and have them flusg the brakes.

BTW, if you look at the manual there's a thing at the front of the distribution block you're supposed to keep from slipping forward. Is your brake light on? I'd guess this is the problem.

[del0075]

ok more update, i have unhooked the proportion valve, and swapped the front and rear brake lines. still have no front brakes, unhooked the rear brakes and plugged the master cylinder, i have front brakes a little. cant get them to lock up, and the pedal is harder to push.........


i am wondering if there could be an issue with the new booster....

[del0075]

well i put new rotors on today, and re bled the brakes again....... still nothing

[plummen]

put a brick or something heavy on brake pedal and let it sit overnight then try bleeding brakes again,might be suprised how many big bubbles you get from system that way