Power Steering Small Noise at Idle ONLY

[pokeyl]

Only at idle with the heat above 90F and the AC on high and I have to make steering input. As soon as the RPM is above 1000, Zero noise.

I think the pump is weak and can't supply both the Fan system and Steering at low RPM.

I need to see if the prior owner changed to an under drive pulley.

The fluid is Red, but I have not changed it yet, fluid age, very old, the car only moved 1700 miles in 7 years.

[St.Char]

Complete fluid change. Sounds like your fluid is breaking down .

[Steve-Indy]

As suggested, change P/S fluid...Mopar ATF+4.

[pokeyl]

Changed used ATF+4 autozone brand, noise is gone. Thanks

[Viper Specialty]

For what its worth, USE MOPAR FLUIDS ONLY, especially with that fan system.

[pokeyl]

For what its worth, USE MOPAR FLUIDS ONLY, especially with that fan system.


Copy, it started making the noise again last night, worked fine 50 miles.

[Viper Specialty]

Copy, it started making the noise again last night, worked fine 50 miles.

That is very suspect. I don't think your problem was actually the fluid.

Explain this "noise".

A vibration/slight buzz when the fan is cranking at high speed *and* you are turning the steering wheel is normal, as you can feel the fan through the steering since they are hydraulically linked.

[pokeyl]

Only when I turn the wheel. I can feel the noise vibration in the wheel. if the RPM is above 1000 I can not hear or feel anything. I have worked hydro systems on aircraft for over 35 years and it seems like flow is low at idle with the AC on. this may be normal with this system. The wheel is not hard to turn, just a hum, like a pump is working at the limit to supply to both the fan and PS unit.

It would be good design to have the pump at limit at idle, we only need what we need. No wasted power that way.

Based on your statement I think it is all normal. I still needed to change the fluid. I used Castrol not Autozone I looked last night.

[Viper Specialty]

Only when I turn the wheel. I can feel the noise vibration in the wheel. if the RPM is above 1000 I can not hear or feel anything. I have worked hydro systems on aircraft for over 35 years and it seems like flow is low at idle with the AC on. this may be normal with this system. The wheel is not hard to turn, just a hum, like a pump is working at the limit to supply to both the fan and PS unit.

It would be good design to have the pump at limit at idle, we only need what we need. No wasted power that way.

Based on your statement I think it is all normal. I still needed to change the fluid. I used Castrol not Autozone I looked last night.

What you are describing sounds normal, yes. It is likely only noticeable when the outdoor temp is very high, and the A/C is on, as the fan will ramp to its high limit.

The fan actually does a variable routine, as it is PWM controlled. While it does have a target temp, it is limited to about 45% duty cycle at idle speeds w/AC Off, or 55% w/AC On. I do not think what we are feeling is the system running out of flow [as the steering would become difficult if the pressure actually dropped off] but rather we are feeling the pressure RISE due to the steering action not bypassing like normal. You can feel the pulsation through the steering wheel more readily due to the higher pressure operation and higher duty cycle of the solenoid. The pulsation is caused by the pressure rise/drop every time the valve actuates, as when the steering is operating at high pressure, and the fan is operating at lower pressure [as it would be at a flow rate below its maximum possible speed], the fluid direction will be switching "exit orifice" of different head pressures, producing a fluid pressure harmonic. The valve operates at 200Hz if I recall, which is about right for this "buzz". At higher RPM's and flow rates, this is likely dampened as the stable pressure between orifices should balance a bit better as the fan matches more closely to the steering rack nominal head pressure.

[pokeyl]

200Hz is about right for the freq that I hear/feel. Thanks