Stick-slip power steering problem--how to fix???

[Kaboomba]

Howdy all. I have a curious problem with my power steering in my 94 Buick Park Avenue.

Problem: Momentary lock-up or "sticking" of the steering wheel during normal use

Trends:

1. Happens on approx 1 of every 12 or so turns
2. Has occurred at nearly every position in the range of available turn radii
3. Occurs only when steering wheel is held in a given position for a moment or more (NOT while actively turning the steering wheel)
4. Lasts only a moment or two, then "releases" and operates normally
5. There are no abnormal noises from any part of the car
6. Has occurred at every possible fluid temperature
7. Happens slightly less frequently after fluid was flushed and LubeGard Power Steering Flush was added

Background:

Steering feels slightly heavier than my brother's '93 Park Avenue steering. Steering is slightly lighter after flush and LG additives.

Service records show that this car suffered from a defective shaft seal, which was fixed with 20K mi on the car (it had 28K when I bought it)

P/S has never made inordinate noise

 

[SuperDave456]

I would keep flushing it.
Every 3,000 miles or so use a turkey baster and pull out the old stuff and put in new stuff.
If you don't start seeing results you may want to disconnect the low pressure return line to the reservoir and drain off a bunch of it and go with some type of synthetic ATF.
It sounds like you have a buildup of crud in there and your flushing has been getting rid of it gradually. Perhaps try some Auto RX.

P/S lines will break down over time. My sister has a car that I took a look at and the P/S fluid was BLACK and had a "bump" when you turned the wheel. I drained off what I could, turkey baster method, put in Mobil 1 multivehicle ATF and some Auto RX. Then did another turkey baster and Mobil 1 routine 3000 miles later. It is still dark, but she isn't having any troubles.

 

[Boomer]

This kind of behavior is often found in rack and pinion units as they fail. If this is R&P (not sure what is in your car), you'll need an entire new system. GM had a lot of problems with these over the years.

 

[UNC017]

What you're describing almost sounds like intermittent slippage of the PS belt... is that belt glazed, oily, undertightened (assuming its not a serpentine). If its a serpentine, then I'd expect other things to be having similar problems alternator voltage dropping, AC cutting out, etc.)

My next guess would be a control valve in the steering rack itself.

 

[Kaboomba]

This is a R&P.

The belt is in great shape--a nice, almost-new Gates.

It seems premature for a R&P unit to fail at 80K mi--I haven't heard that complaint about these cars. Could be, though.

Is there usually a low-point with a plug that would allow me to drain the system? Anybody know?

K

 

[mechtech2]

Even a new belt can slip if a tensioner is faulty. Also an idler pulley can act goofy.
Is your tensioner spring loaded?
Any chance the drive pulley on the PS unit is slipping? Rare, but possible.
It is possible that when the seal went bad, the reservoir went dry and cause damage that is only now becoming evident.

 

[Kestas]

Isn't this the well-known problem of the seal wearing into the aluminum housing? This usually presents itself in the morning before the car has warmed up. Or am I thinking of a different problem?

There was a shop about 50 feet away from where I used to work that did nothing but rebuild steering racks. They told me about this problem with GM racks from that era. Their fix was to machine out the groove in the aluminum housing and sleeve it with steel, as it should have been manufactured in the first place!

 

[Kaboomba]

If you are referring to the seal on the piston (the one that provides the assist to the rack) internal to the rack housing: I think that could be possible. This problem can happen at any time.

The sticking can happen anywhere in a range of rack displacements (usually on the right side, it seems).