My buddy has a 1978 f 150 4 x 4 with a 351m 400 . The power steering quit awhile back so he decided to get a new pump and new power steering box. [possibly rebuilt] . The problem is that we cannot get any power steering out of it . The steering wheel is hard to turn as if it didn't have any power steering at all. All the lines were hooked up correct and fluid put in , tried the front wheels off the ground while turning the wheel and still nothing. He has been through 2 new pumps and 2 different boxes , on the last try the line fitting cracked and started leaking , lines are clean clear through.
IS there something anyone knows to try to solve this ? A process to go through ? very frustrating !!!

 

When bleeding the air out of the system, it is best to have the wheels off, while the truck is on jacks. This will allow maximum movement for the air bleed. Another thing you can do is fill all available lines before connecting to the pump. This will allow for less air to bleed out. Good luck.

 

We tried the wheels off the ground and its does nothing , barely makes a growling sound but can see the moving in the pump resivour.

 

I don't see how this could happen because the fittings are different sizes, but is there a possibility that the hoses are reversed?
The pressure hose goes to the fitting closest to the sector shaft cover, the return line connects to the fitting closest to the steering shaft.
Here's the illustration from the parts catalog:

 

I went through three rebuilt pumps one time before I got a good one. I later figured out the relief valve in the pump was stuck and not building pressure. it is behind the pressure line fitting on the pump. take the big nut out and it should be inside with a spring. I even flushed the box on the first one. Good luck.

 

I struggled with my 79 after replacing the steering box. First, no assist. Then, after getting some assist, the pump was very noisy.


The instructions with the steering box (which I elected not to read right away as I know everything) said to jack the truck up, and cycle the box back and forth 20 times without the engine running. Then, let the truck sit for at least an hour, but preferably overnight.


Then, cycle the wheel back and forth 10 times without the truck running. Mind you, you need to keep an eye on the fluid through all of this.


After that, I started the truck and shut it off several times so I could add fluid and not starve the system.


Once the truck is started and running and the fluid level has stabilized, cycle the wheel back and forth several times (like 30-40) and slightly bumping the stops in the steering box (that is what seems to eradicate the most air hence stopping the noise). When the truck is running, the fluid level should be right at the bottom of the reservoir. If you fill it higher that that, it makes an awful mess when the truck is shut off.


Ironically, all of that worked.


Hope this helps some. I could not believe how I struggled with this. It should be a simple system but when you research it, this is one of those items on these trucks that stumps most everyone.


Tim