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1999 STS - diamond white
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Discussion Starter · #1 ·
My '99 STS has 104K miles. I get an oscillation in the steering wheel when I make slow, sharp turns into a driveway. The fluid level is fine, I even changed it a few years back. I thought maybe the serpentine belt might be slipping. It's original so it was due anyway. It still oscillates. I did make note while I was changing the belt that I could tug on it and the tensioner moves easily. Is this normal? Could my tensioner be causing the problem? There's no squealing, just a subtle vibration in the wheel. Any ideas?
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
My '99 STS has 104K miles. I get an oscillation in the steering wheel when I make slow, sharp turns into a driveway. The fluid level is fine, I even changed it a few years back. I thought maybe the serpentine belt might be slipping. It's original so it was due anyway. It still oscillates. I did make note while I was changing the belt that I could tug on it and the tensioner moves easily. Is this normal? Could my tensioner be causing the problem? There's no squealing, just a subtle vibration in the wheel. Any ideas?
I'll "suggest" that what you are feeling is normal for a "sharp turn" IF sharp turn means to full-lock. It is not unusual, at very slow speeds, to feel the constant velocity joints rotate at the turning motion limits of the constant velocity joint's ability to transfer torque smoothly.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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I did make note while I was changing the belt that I could tug on it and the tensioner moves easily
How easy is "easily" - as in: pull/push on the long flat belt run and the tensioner moves 1" ? Or pull/push and get 1/4" ?

Can you tie this oscillation to tire/wheel rotations - a bad wheel would have one "wheel pull" per revolution, the CV joint would have 3 or 6 (they have a 3-node inner coupling and a 6 node outer flex joint), while a slipping pump pulley could be any random movement.

I believe that the 99 also has magnetic steering effort control. This may be a culprit. Any codes ?
 

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99 STS, White Diamond
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792 Posts
Is the car new to you and the effect quite subtle rather like the feeling when a magnet is moved from a surface and suddenly looses attraction?

If so, I believe you are feeling a normal artifact of the Magnasteer variable effort power steering. I recall this being mentioned by reviewers when the cars were brand new.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter · #5 ·
I've had the car for about 5 years. This is a new feeling. The wheels are not hard over but almost. It has that "magnetic" feeling. Maybe it is normal.
I can grab the belt, pull firmly on it and the tension deflects maybe an inch. Thought it might be related.
 

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99 STS, White Diamond
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792 Posts
After five years you know your car and a new feeling...

That's the same deflection I just felt on my belt with a firm tug or push. To me it seems a very good tension level.

Judgding by posts here and my own car, I suspect you're at the very beginning of the end of service life of your power steering pump. If so, over time and on occasion you will probably feel sudden and brief (almost instant) loss of power steering as you turn sharply to park.

Now I understand the "grab" you talk about. I've felt it on occasion--as well as that momentary complete loss--and the steering pump is high on my list of things to replace...
 

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1999 STS - diamond white
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Discussion Starter · #7 ·
Thanks for the posts. I'll leave the tensioner alone and just monitor the behavior in the future.
 
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