Drove about 100 miles to maine no problems. Just went to drive the truck and have no power steering, truck still warm. Res is full and no apparent leaks. Will come back on when truck is in motion but not every time. Pump maybe, is there a fuse to check? Any help appreciated, thoughts on what to check etc. Also no check engine lights or anything. Truck is an 05 st 4x4 6 speed.

 

Check the U-joint on the steering shaft, beside the LH exhaust manifold.

 

Try removing the power steering return lines as if you were doing a fluid change to see if the power steering pump is working. And I wouldn't recommend driving far without power steering as that U-joint isn't meant to be load bearing.

 

you can also check the pump by removing the cap on the reservoir and turning on the truck. when turning the wheel, the level of fluid should change a little between states (turning and not turning). When turning, the fluid should go down a bit as you are using more pressure to force push the wheels. you should also see the fluid moving around while not turning the wheel (ie, fluing going in and fluid going out) kinda like a swooshing motion. You can also put your hand covering the reservoir hole, and see if you feel some vacuum, which you should. If not, then the issue is with the pump.

And if fluid just sloshes out the top of the reservoir then one of the lines is plugged, or is leaking, pulling in air and bubbling through the reservoir.

You should also look at the lines, if the return lines are compressed (being sucked in) when the reservoir cap is closed, then then there are issues either in the rack or one of the other lines are clogged. If the pressure lines are bulging, then your rack is not getting enough pressure so it feels like you don't have power steering.

Lets hope you find it in the lines or the pump, because the rack can be expensive to replace.

 

So just to update... Later in the weekend on the way home, started the truck still no power steering but 1 minute in while backing out of the driveway my tire shifted levels from driveway to lawn and steering was back. Drove 50 miles with it working perfectly, stopped and turned off the truck came back about 30 min later and no power steering again for the remainder of the ride home. Next day at work drove fine but later in the day it lost power on a sharp turn but only for a split second and it was back. My mechanic drove it for two days without being able to get it to lose power so hopefully this issue was just an anomaly which unfortunately will leave me wondering when it will happen again.

Am going to check as you have suggested taking the cap off and checking the fluid if the levels change and see if there is vacuum and if the issue happens again will also check it during that time.

Thanks for the replies, will keep an update if anything changes but the only other oddity to mention is the cylinder 5 just started reading a misfire..can't see how either could be related but only mention because of the timing of the two issues.

Would also like to note that despite all this I am still very glad it is not a Ford so at least there's that.

 

Power steering rack is shot.