Chevrolet Repair/Power Steering Pump Whine
QUESTION: I've twice replaced the PS pump on my '02 GP (3.8 NA) because the original was making an awful growl on sub-zero temperature mornings. Both (remanufactured) pumps are now making the same high-pitch whine after the air was bled. I flushed out 1 quart of fluid after each install. There are no leaks. Pump No. 2 has been in service for 7 days with no change in the noise.
The "whine" remains the same hot or cold, whether turning the wheels or driving in a straight line. The pitch increases only with engine RPM. There are no visible bubbles or foam in the fluid. Lines look O/K too.
Is it possible that there is still some air trapped in the system after several days of driving. Could the vent cap be bad?
I can't believe that both remanufactured pumps are bad. The noise was identical for both.
Any suggestions would be most welcome.
ANSWER: Maybe the power steering pump is not the problem. There is another hydraulic pump , similar to the p/s pump in the transmission. Its called the front pump and can sound alot like the noise you are hearing comming from the p/s pump. Does it change with the turning of the steering wheel? Let me know.
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QUESTION: The transmission's front pump is noisy too, but only for the first minute or two after a cold start. Not uncommon for a 4T60-E Trans of that vintage.
The noise in question is definitely the PS pump. Can hear it through the stethoscope. Aside from the noise steering works fine. The noise does not change when you turn the wheels but is most noticeable during acceleration. Sounds like a supercharger.
Is it possible there's still some air in the unit after several days of driving. Would a vacuum bleed help?
I've seen this before with a car I repaired a few years ago. I also had been through a couple of rebuilt pumps leaving me puzzled like you are now. I finally went ahead and returned the second pump and installed a factory pump and the noise vanished. I don't know for sure ,but I think that these reman houses give the stamp of approval more often then not when it comes to how noisy they are.they function like normal except for the noise. Most pumps that they receive are defective due to seal leaks or some other cause that is not related to noise. so they just slap a generic rebuild kit in them after a good cleaning and then paint them and call it good so what you get is a nice and shiney noisy pump. I doubt you have air to bleed in the hydraulics and a pump even under max load, like when steering is forced at it left or right end of travel (or lock) where you can not turn the steering wheel any further it should not have a noticeable whine. you may hear fluid cycling under extreme pressure past the pressure bypass valve, but still there should be no whine. I say this because any steering box issue or rack issue or other related power steering issue,as long as fluid is good should not make the pump whine as you describe.So if I were in your shoes I would go OEM original equipment. Good luck. P.S. You are using the correct fluid and purged the system ,correct?