D250E hydraulics wont work when cold

I just bought a D250E 5TN s/n and as stated the hydraulics do not work when it is cold. I would expect them to be slow when it is around 0, at least until it warms up, but it seems like there could be something wrong. The other day they delivered the truck (loaded it the night before, was -4F that morning think it was 8 or 9 when it got there) and it would just barely steer, not even think about lifting the box. I let it sit in the yard running for about 2 hours and it would steer slightly better, put it in the shop for a couple hours and then it seems to work fine - about 8 seconds to turn from lock to lock at idle, 6 at full speed, raise the box at full throttle about 20 seconds. The dealer I bought it from insisted that it needs a new power steering pump, but I am thinking that the pump is alright as if it was worn it should get weaker as the oil warms up, not the other way around? I am thinking it may be a relief valve issue? Any ideas?

Where was the machine before you purchase it? Might have the wrong oil in the system for your climate.

It came from another contractor about 200 miles west of me. It had the oil & filters changed just before I got it, it is the same aw46 that I run in my other equipment, have not had problems with anything else.

I've had issues in the past with earlier machines having problems in the lift cylinders making metal and pitching it into the hydraulic valves. As I recall the box valve and steering valve are in the same body. The junk would hit the valve and there was a ball resolver that would get held open and dump pump flow back to tank. When you lift the box does it drift down slowly?

Yes it does

The cylinders used to use set screws to lock the pistons in place on the rods. It has been my experience that in time those set screws back out agains the barrels and start shaving metal that contaminates the system. I would suggest pulling the return filters before you go any farther.

Yep, and check suction screens if any, and look for kinks or restrictions in the suction line from tank to pumps. Sounds to me like it's starving the pumps.

Today I pulled the filter and felt around the bottom of the filter housing, there were a few small pieces of rubber - probably an old seal or o-ring, but no steel shavings. To get to the suction screens (if it has them) I would have to take the tank apart, and if there were that many shavings that it was plugging the lines there would at least be some in the filters or filter housing. Am I correct on this or should I quit being lazy and take it apart? I also called the dealer and (I don't have a parts book) from looking in the parts book they told me there are no set screws in any of the cylinders on this model truck. Not ruling out a restriction in suction lines yet, but they look good from the outside, and are wire reinforced, so it seems unlikely. I kind of like the junk in the valve idea, makes sense with the way it is acting. Of course if that is it, then the question will be where did the junk come from?

The hoist cylinders are apparently single stage and just use a big nut to hold the piston on. Just saw a diagram of the steering cylinder and there is some kind of ball valve inside and what they are calling a grub plug going into the side of the piston. There is a similar setup on the tail gate cylinder if you have this option. I don't see a nut like I would have expected. I have seen something like this on other manufactures where they hold the piston from turned with a set screw and then pound a plastic plug on top of it to keep it from backing into the barrel.

I'm with you on the tank. If there isn't much in there or the return filters you most likely don't have something real catastrophic. I would recommend you have the dealer send you a PDF of the parts page so you can see what is in there and decide what you could do next.

If you need any parts diagrams send me a PM with your email adress and the machine Serial Number and indicate what you're looking for.

Think we finally solved this one. Went through the testing procedures in the documents that Nige sent me, determined that the left side pump was shot. One reman pump later and everything works like it should. We suspect that with only one working pump it was losing prime from the tank when it sat overnight, thought it might be weak too, but it was up to spec on relief pressure, so we are going to run it. Thanks John, lantraxco, and Nige, for all the help.