Truck: 1996 F150 4.9 M5OD 4x2

I've noticed that I don't get any kind of power steering assist when I first start up a cold truck (ie when the temperature is lower than 40F).

I have to start up the truck, let it idle for a few seconds, then start to rock the steering wheel back and forth a few times. Eventually, I will feel the power steering kick in and then I'm all good. This gets worse (ie I have to rock it back and forth longer) the colder it gets outside.

I've checked the fluid, and its full. Fluid color is good, no metallic particles. I've done two fluid changes (just a drain and re-fill of the reservoir). Refilled with Mobil 1 Synthetic ATF.

Thoughts on why I'm getting this issue? Or is this normal? Do you all think this a pump or steering box issue?

 

This probably won't help much, but I had the same issue with my Bronco. Problem stayed when I replaced the steering box and went away when I replaced the pump (I was changing the accessory drive from an '88 F-150 serpentine setup back to an early Bronco V-belt and had to replace the F-150 pump with one for a Bronco)

 

I thought the OBS trucks only took Type F trans fluid for power steering...I don't know what was spec for that '96 OBS, but both my '92's require Type F. Other than that, Mercon V or dino Mercon was too slippery for power steering. There was notion or known fact that Type F had more friction particles

If this isn't the case, according to the '96 service manual, then perhaps as Nothing Special said, it may be time for a new power steering pump.

 

Oh crap. You're right. I just checked my manual. I'll try to change it out with Type F.

 

Here's what I do:

-Buy 3 or 4 quarts of the required fluid.
-Jack the front of the truck up and use jack stands to hold it just so the tires are off the ground. (Follow standard safety procedures when lifting a vehicle!)
-Siphon out the fluid in the pump reservoir with an old turkey baster (label it somehow so it won't wind back up in the kitchen!)
-Fill reservoir with new fluid and replace cap
-Start the engine and turn the steering wheel from lock-to-lock (back and forth completely) for 15-20 or so cycles.
-Shut off the engine and siphon out the now dirty fluid in the pump reservoir.
-Fill it back up with fresh fluid, replace the cap, and again start the engine and turn it lock-to-lock about 20 times.
-Repeat this process until the fluid you extract from the reservoir is clean. Usually takes about 2-3 quarts depending on the system size. You might be surprised how dirty the fluid remains after a few cycles.

It sounds like this process may take a long time, but it really doesn't. I think it takes anywhere from 20-30 minutes (depending how dirty the fluid remains and if you have a helper!), and at the cost of a few quarts of ATF fluid, it's pretty cheap.

With this process, I've cured systems that intermittently lose power steering when cold, loud GM style pumps that sounded like the pumps had failed, and I've also cured a Lincoln system that would loose power steering when turning one direction.

Give it a shot!