Im having a problem with my 79 f150 4x4 I was wheeling and all my fluid blue out the pitman arm seal on the steering box. i have rebuilt it all new seals and while bleeding it, it blew the new seal could that have been because of air in the system im getting ready to replace the seal again so third seal and would like it to work this time. If you have any info please share it thanks.

 

Did you put the snap ring back in? And there should be two seals, not one.
The parts catalog shows there should be a seal, a washer, a seal, a washer and last a snap ring.
Here's the illustration.

 

Here....have a read.

https://www.ford-trucks.com/forums/1...ering-fix.html

And a little more....

On the vehicle...
Remove the pitman arm from the sector shaft, then there's a snap ring that needs to be removed. Once that's out of the way there is a washer, then a seal, then another washer and another seal.
Remove the first washer exposing the first seal. Take a sharp center punch and pierce the seal, screw in a sheet metal screw and pry the seal out. You can do two screws 180 degrees apart too.
Once the first seal is out, remove the second washer and repeat the process.
To replace the seals, apply a thin coating of grease to the inner lip of the seal and a thin coat of sealer to the outside diameter of the seal (I like No. 2 Permatex non-hardening).
Slide the seal over the shaft and take a deep socket thats just slightly smaller than the OD of the seal and drive the seal in untill it seats. Replace the washer then the next seal, washer then snap ring.
Reinstall the pitman arm, hook up the steering linkage and that's it.
If you don't have a socket that's deep enough you can use a piece of pipe or tubing too.
Here's an illustration from the Ford parts catalog showing all the parts involved in the steering gear. The killer on these is getting everything centered. With the exception of the sector shaft Ford basically only sold the internals as an assembly.

Seal kit, steering gear sector shaft
Parts list #64, With gear ID SPA-AB, AJ, AN, BN, BS, BX, CC, CN
Basically this covers all 73-79 2WD F100-350 w/ power steering
D7AZ-3E501-A
Last dealer cost $29.41 List $43.71

Parts International, Farmers Branch, TX has 50 (972) 241-8730
Green Sales, Cincinnati, OH has 19 (800) 543-4959
Manderbach Ford, Temple, PA has 5 (610) 929-3683
Freese Motor Inc., Monticello, IA has 4 (319) 465-3541
Herb Chambers Ford, Westboro, MA has 2 (508) 366-8311
https://www.ford-trucks.com/forums/1...+steering+seal