QuestionQUESTION: I have a 1990 944 S2 and a whining sound has developed over time.
It appears to come from the power steering pump area. It also only occurs at revs from about 1500rpm to 2300rpm, at other revs it goes away. The pitch stays constant over the rev range. Any ideas before I start stripping it down?
Thought it could be:
P/S pump, P/S belt, P/S bearing.
Any help would be appreciated.
ANSWER: Noise from power steering generally is isolated to three areas:
A) Resonance from power steering lines (not secured).
B) The power steering pump (loose pulley, damaged pulley, belt issues, pump mechanicals or noise related to cavitation; air in the system).
C) The power steering rack or box (the "growl" or groan associated with spool valve failure).
Assuming you describe the noise as a "whine" rather than a lower frequency (ie. a rumble), and you have isolated the noise at or near the pump:
1) Inspect the pump pulley to insure it is not damaged (not bent, not lose, no burr's on the edges).
2) Inspect the belt for glazing, alignment, tension and frays. Excessive tension typically is associated with a 'whine'.
3) If you have had a leak in the past, such as a leaking power steering rack (whether you are aware of a past leak or experienced by the previous owner) the pump could be damaged from running dry or it has been damaged by contaminants in the system. If you have had to add fluid (Dexron ATF in this case - only) then the system had a leak.
What is the age of the current pump?
i) don't know
ii) guess it's original
iii) recently rebuilt
iv) new
Are you aware of any repairs to the power steering system (records)?
---------- FOLLOW-UP ----------
QUESTION: Firstly thanks for the response.
Just some further info:
1) This only happens after a while after driving. Never at start-up even when the car has been standing for a short while.
2) The are no signs of leaks. The fluid level is constant.
3) I can feel a slight vibration on the steering wheel at the time it occurs.
4) The pitch is constant regardless of RPM.
4) The whine isn't affected by the turning of the steering wheel.
5) The whine also comes and goes, not always present.
6) I assume the pump is original. No sevice history of pump issues. It started at about 120 000km and is now at 160 000km.
A) I will check the lines as suggested.
B) The belt looks like it may be glazed.
C) Is there a way to bleed the system?
Thank you for the great feedback - it's appreciated.
Mike
AnswerYou should not have to bleed the system unless a component was replaced, a line was opened or the system ran low on ATF.
You can bleed the system by turning the steering wheel (rack) left and right to its fullest point several times,however do not hold it forcefully at the end point.
If you see air bubbles in the fluid in the PS tank then you have a leak on the suction side.
160000km is 99419 miles. That is a long time on a ps pump. And since
you don't know the history of the ps system then potentially the problem could simply be a worn pump; sounding like after the fluid has increased in temperature the noise occurs.
A new aftermarket pump is about $199.00,no core deposit.
A OEM remanufactured unit lists for $360 plus $50 core deposit.
Usually glaze belts slip and squeal under load.
