Brake bleeding questions

[jricharc]

I have a '70 C10 with power drum brakes, I replaced the intermediate line along with a few other lines on the truck and put on a new Master Cylinder. Now I have a soft pedal and have been trying to bleed the brakes and can't get any fluid to the right rear wheel, I bench bleed the MC and had a hard pedal but as soon as I hooked up then lines my pedal went soft. I am not losing any fluid so does my proportions valve need to be reset?

[Ta12sec]

I think you posted in the wrong section but I'll give you my thoughts.
No fluid to one wheel on that truck is a blockage in the line between the T at the axle and the wheel cylinder .

[Liz]

ttt for some replies. This was posted in an incorrect area and overlooked.

[Ta12sec]

If your not getting fluid to the bleeder on the wheel cylinder, work backwards from there open the line at the w\c, no fluid open the line at the axle T if you have fluid there and nothing to the w\c your blocked.

[davepl]

Assuming you're getting it to the left rear wheel then the main rear line is working. Must be plugged with debris at the T junction or the right rear bleeder isn't really open (or it's somehow plugged).

Leave only the right rear bleeder open and mash the pedal, does it flow? Not at all? Is the pedal firm against it?

[tdangle]

I had a similar problem. Turned out the wheel cylinder was plugged not allowing fluid to go out the bleeder passage.

[cdowns]

you do not have a proportioning valve on that year just a simple distribution block was used

[AWKS1]

I had a similar situation where the right wheel cylinder only had a dribble of fluid coming out of it after I had replaced the wheel cylinders. my proportioning valve was stuck. after several failed attempts to re-set it, I threw in the towel and replaced it with a new one. fixed the problem. does your dash light come on?

[mike16]

Originally Posted by AWKS1

I had a similar situation where the right wheel cylinder only had a dribble of fluid coming out of it after I had replaced the wheel cylinders. my proportioning valve was stuck. after several failed attempts to re-set it, I threw in the towel and replaced it with a new one. fixed the problem. does your dash light come on?

x2. but befor you buy a new perportioning/distribution valve remove the old one and slosh it around in som 92% isoprople alcohol. flush it out. read in your service manual about centering the piston in the perportioning/distribution valve. reinstall it and service the brakes according to the service manual. if that fails. then start at the mc and remove and flush/ blow out each line with compressed air and push fluid through untill you find the blockage. the bleader valve can be corroded inside wher its threaded to the wheel cylinder. remove it without braking it off. clean it up inside and out and probe the hole with stiff wire to uncloge it. if that does not work pull all the wheel cylinders and rebuild them.

service manual is great but keep in mind that it was used buy the dealerships to service new vehicles under warenty. our vehicles are 40 plus years old and have a hoste of additional problems that challenge our trouble shooting skills. Usually when you find a problem its a symptom of a need to service and maybe overhual the entire system. its called shotgun maintenence and can be expensive but its also a way of symply eliminating doubt or uncertainty about components within the system. go through every thing to learn about the system and to eliminate uncertainty. Its a brake system so you want to remove all doubt. It part of the game in this hobby. its an accepted reality. have fun and learn and share your success. we love pictures too.

[jricharc]

Thanks for all the replies, I replaced the Master Cylinder and still had a spongy pedal so I am just getting back to messing with this thing so I will pull all the wheels off again and see if any of the wheels cylinders seem to be the cause.

[GRX]

Being that you replaced several lines and the master there could still be a small bubble or two in the system. Does not take much. Bleed then bleed some more.

[jricharc]

Thanks, I will try that, I was getting good dripping from the rear lines and the fronts as well. I left the right rear bleeder open for about a week and let it gravity bleed and then did the rest so I am going to pull all the wheels this weekend.