ok guys i have taken on a new rat rod project, its a 71 f100 with a 400 motor in it..its going good but im having trouble with the brakes...i started to bleed today and i would have the brakes pumped and after about 3 times the fluid just stopped coming out..so i figured one of the lines has collapsed..what do yall think? also does this truck have a proportion valve? if not then what is the box in the frame rail under the drivers side..let me know thanks!

 

Yes, that's the proportioning valve. It has an electrical connector that goes to the brake light near your ignition switch.

 

ok thanks..do you have any idea what my problem is?

 

Could be a plugged line, a bad distribution block, or prop valve.

You need to do more troubleshooting and post more info....Which line/nipple were you bleeding? You need to isolate which line may be plugged. The correct sequence is the furthest bleeder to the closest bleeder in the system (RR-LR-RF-LF). If the rear, try bleeding the opposite nipple. If it bleeds, then the line is obstructed between the distribution block mounted on the axle and the non-functioning bleeder.

If the front, then figure out which line is plugged since each front brake has its own line originating from the prop valve.

Post your results.

 

i bled the RR and fluid came out and then air and fluid so i kept bleeding then nothing came out..so i went to the LR and nothing came out at all. and im bleeding the bleeders on the back of the drums

 

Okay, so now we know the rear circuit (one of three coming out of the prop valve) doesn't have fluid. The MC is topped up, right? OK.

There is no going back so disconnect the hardlines connected to the distribution block mounted on the rear axle and disconnect the rear circuit from the prop valve. Blow it out with compressed air. Observe the stuff that gets blown out. Reconnect the lines and try bleeding the RR and LR again. Avoid stomping on the pedal... do it slowly.

Got fluid? Good.

No fluid? Bleed the RF and LF circuits.

Got fluid from the fronts? Yes means the prop valve has defaulted and its internal piston has moved to block the failed (rear) circuit thus preserving your front brakes. No fluid from any of the three circuits likely means there is an internal failure within master cylinder. A rebuild kit is about $25... super easy.

Resetting the prop valve... remove from vehicle and remove the brake switch. Look inside and you will see a piston. Using a jeweler's screwdriver, reach in and coax (pronounces "cokes") the piston forward or back so is approximately centered and the detente groove is centered... the groove is where the actuating pin of the switch rests in. When the piston moves off of center, the pin rises and grounds the brake light switch. The piston also moves to block the failed output port.

Reinstall and bleed the system. Again, do not stomp on the brake pedal or else the piston will move offcenter again and you'll have to repeat the process. If able, allow the system to gravity bleed.

 

Likely the rubber line going to the rear axle is plugged up. Typical issue after many, many years of use.

 

The way i bleeds brakes by myself is.

I start at the right rear and open up the valve a small amount.
I then attach a hose on it and place the end of it in a clear container i can see though with some brake fluid in it.
I slowly pump the brake pedal and watch the bubbles in the fluid as it rises .
When the bubbles stop i close off the valve before lifting the hose out of the container. If you lift the hose out first you will let air back in.
Then i go onto the next one and repeat until i get them all.
All during this i keep checking the master cylinder and keep it topped of so as to not get more air back in.

Now you ask ' how do i see the container and pump the brake pedal' ?
Easy, i place the truck on jack stands, sit beside it so i can see each wheel and with a 6 foot long pole in my hand i push on the brake pedal.

When you live out in the country with no body to help , you just find a way to do it or drag it to some shop. I like doing all i can myself.

You can buy brake bleeding tools i guess but I do it on the cheap , just take a little longer some times .

 

One of the first things, I learn while working in a brake shop wow,,, 50 yrs ago is never push the brake pedal all the way down to the floor while bleeding the system as the rubber MC cup can stick in end of the cylinder behind the piston from all the old crap that builds up over the yrs and cause it to fail and let fluid leak pass the cup. Then you have to rebuild the MC on top of just doing the wheel cylinder bleeding. This could also be your problem. if none of the others..orich