Intermittent Loss of Power Steering

[Rapidtransit]

My 2001 Lincoln LS v8 exhibited a intermittent loss of power steering today for the first time.
When I realized what was happening, I stopped the car with the engine idling and expected to see power steering fluid all over the place. To my surprise, all the hoses and fluid level were normal with no apparent leaks.
So, periodically while driving in stop and go traffic while turing the wheel it felt like there was a momentary loss of power streering fluid with that characteristic power steering noise.

Could this be a defective power steering pump or possibly a sensor problem? Any further information would be appreciated.

 

[joegr]

Yes, but other (possibly more likely) possibilities are a failing rack or a slipping drive belt.

 

[Telco]

The first assumption, since there was no other problems, would be that the fluid needs to be flushed. If it continues after flushing the fluid, you can start looking at hard part problems. Fluid does wear out, lose lubricity, collect water, ect.

While flushing the fluid, check the condition of the accessory belt.

 

[Rapidtransit]

Every year or so, I would suction out the fluid in the reservoir and replace with Mercon 5 fluid. The accessory belt was replaced about 6 years ago which amounts to about 100K miles on the existing belt. There's 209K miles on the odometer now. I will remove the fluid reservoir and clean it out. Can I use compressed air to remove fluid in the rack?
I had noticed that I hear a moaning sound only after the car warms up, which I could never identity. After today, I'm getting the feeling it's the power steering pump. I don't think the failing of the steering rack would cause a moaning sound.

 

[joegr]

With that added info, the pump does become a bigger suspect.

 

[Rapidtransit]

Just went out to make some further checks. No leaks and the fluid reservoir is full. While the car is idling, I can turn the wheel to the right with no issues, but turning to the left, it will bind and make that power steering growl. I'm now thinking that some valve must be sticking in the steering rack. Tomorrow I'll get some Seafoam trans clean and maybe if I'm lucky it will free up whatever is stuck.

 

[lsintoronto]

Interesting - I was backing into a parking spot last night and at that low speed the steering went from easy/light to heavy, almost like a temporary reduction in power assist. I was fine when I drove it a couple hours later and the fluid level looked fine.

From the few threads I've found it looks like an early signal that there is an issue with fluid or actuator or rack or pump. Will have to do some investigation this weekend and hopefully it's a little warmer!