2004 G35X 220K miles.
About 6 months ago I had a PS fluid leak and wound up replacing the rack and pinion assembly. Now, all of a sudden, my power steering sporatically becomes really hard to turn. It's always changing. At first, it was hard then easy then hard again as I turned the wheel. Then.. suddenly, it was operating smoothly for a couple of days... then over the next couple of days it started getting more difficult. This morning I had to drive it early and it took all my strength to turn it to get it out of the drive way. Once driving it's easy to steer unless taking a 90 degree turn. It was 19 degrees this morning and when it was driving easier it wasn't as cold... but I can't say for sure it's changes are consistent with temperature fluctuations.
At this point, I don't even know where to look. It's the sporatic nature of this symptom that has me most puzzled.
thanks

 

Probably a rusty steering shaft u-joint. Do a search and you'll get some threads showing examples of how bad this can get. You can DIY it if you're handy. The 06 u-joint (not sure if 04 is the same) is about $100 if I recall correctly. You can confirm if this is your issue by getting in there and shooting some lube on the u-joint. It will make it better for a bit until the lube dries up or gets washed out of the joint. Mine was shockingly rusted up and impossible to swivel by hand once I removed it. The only reason you can overcome the rusty joint is the power steering assist and the leverage on the wheel. If you didn't have power assist, you probably couldn't turn the wheel. Good luck.

 

Thank you so very much.. that was it.. located it.. sprayed it thoroughly with lithium grease and... problem solved for the moment. Will replace soon..