My 2005 altima's steering is stiff. The PS fluid is good. Mechanic changed the serpentine belt that was cracked wondering if that would help, but it didn't. it is making no noise. What should i check next?

Stiff power steering can be the result of low or contaminated power-steering fluid (it may need to be changed or flushed). A loose serpentine belt, a worn out power-steering pump, tie-rod/s or ball-joint/s may be seized, or possibly the rack and pinion may have an internal failure. I listed it in the order that I would check all related items. If you have any questions, findings, or details, please write back. Good luck.

Check power steering reservoir for fluid. Also check for any leaking oil brom your steering rack. If pump is belt driven check your belt for tightness and any cracking. Any cracking and it is time for a new belt. I am going to bet on low fluid though.

Hey Kumar,
Does the steering get easier when it gets hot? If it get easier when hot, its the rack and pinion gear. The valve body (actually a teflon composition ring(s) o-rings/valve bore housing are getting worn to the point where they are not controlling the fluid flow when its cold,, when the rack and pinion gets hot, the valve bore expands and "corrects" the clearance which in turn, controls the fluid flow. The valve body bore in the rack and pinion housing is worn where the teflon rings ride against the bore.
This is nothing that can be fixed except by replacing the entire rack and pinion gear. Drain ALL the power steering fluid from the pump also and fill with fresh new fluid.

I can answer some of your questions without being there in person.
The smell inside the van is from fresh air entering the venting system. Not sure why you don't get it from all vents. The fresh air intake is in front of the windshield and will pick up any smells from the engine compartment.
Loosing the serpentine belt would not necessarily cause you to loose ps fluid, but having a leak could drain the pump and damage the bearings in the pump, causing the pump pulley to drag on the belt.
The ps pump could be in the final stage of failing.
And the shaft seal in the pump could be leaking fluid onto the engine and exhaust.

Sounds like the pump pressure valve is not working when cold and should be replaced.> It is inside the pump where the pressure line connects to the pump.

I would start by checking the fluid. I would than turn my eyes to the pump its self. I would not think it was the belt because that would make sound on start up and the power steering would be stiff.

Have you checked your fluid level???? Is the belt tight?

First tighten the belt up anyway. It may be so wore out it is slipping just the same. If that cures it then get a new belt.

Sounds like a bad steering rack & pinion assembly... is it only bad in one direction or both...?
If both then it's the rack assembly... Hope this helps...;-)

Check fluid and make sure it filled enough,(make sure that its actually power steering fluid in there and not something else added by mistake for ex. antifreeze etc) make sure there are no leaks. Check power steering belt and and make sure its tight NOT loose or slipping. From personal experience with these vehicle you MOST likely cause of this problem if all the items above are GOOD is a bad power steering pump.