A few weeks ago I hopped in my MCS and the steering felt a little tighter when I was at a stop. I wrote it off as paranoia but the problem persisted for a bit, maybe 10-15 minutes. At that point I reached my destination, parked, and had lunch.

Get back to the car after lunch and everything is fine, furthering the paranoia thought. However, on my drive that evening - over the Sepulveda pass in LA to get around 405 traffic - the steering became extremely stiff. The twisty bits were no longer fun but required serious work with both hands to get the wheel moving.

Got it to the shop on a flatbed and of course the problem didn't reoccur. Went ahead and replaced the power steering fluid reservoir as there's a filter in it and some power steering fluid hoses which needed replacement. Got the car back and everything seemed fine until a longer drive had the problem happen again. However, once again the problem fixed itself upon returning to the vehicle.

That brings us to today, the steering is now extremely stiff again. Pulling out of a parking space is hellish. Steering does become looser, though nothing near normal, once the car gets moving a little bit.

Any ideas? Has this happened to anyone else?

 

Sounds like your pump is going out.

 

+1 on the pump. I'd suggest you go underneath and try to spin the PS pump fan. Sometimes those get stuck and cause the pump to overheat and shut down.

 

Like other have said. Sounds like PS Pump. Check the PS fan to make sure it is not stuck or blocked by debris.

 

Other thing to check...
A few folks have had the u-joint on the steering wheel shaft dry out, and get very stiff...

 

also check the FUSE for the PS pump fan....mine wasn't spinning and it ended up being the fuse!