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Whenever I start driving my 97 SE, I hear a high pitch grinding noise, like gears grinding.

It's not very loud, but gets higher in pitch as I go faster, then drops in loudness and pitch when my transmission shifts into 2nd gear, and virtually disappears when it shifts into 3rd gear.

So I checked the transmission fluid level after driving it for 30 miles, and it was on the low side, but within the hash-marks of the dip-stick, and its color was pink but not as light pink as new fluid.

So it seems that my transmission is OK.

Then I added more fluid until it reached the upper hash-tag mark, and the grinding noise was reduced somewhat but it's still there whenever I drive.

Just before I first noticed the grinding noise, I had replaced my power steering pump and hoses (after 22 years) because I had a bad leak somewhere, and added all new fluid per directions in my Haynes manual.

What can cause the grinding noise? Any suggestions?

My thoughts are leaning toward power steering pump or clogged trans filter. Hard to tell without hearing it, obviously.

OK, I just recently heard a sound that's very close to my car's high-pitch grinding noise.

It's the same noise that an oscillating tool makes when it cuts wood, only not nearly as loud.

You may be right about the power steering pump causing the noise, because the noise started after I had replaced it with a new (remanufactured) one. I'll check for bubbles or foaming fluid in my power steering fluid reservoir. If I see bubbles, then it's probably because I didn't purge all the old fluid from the rack after removing the old pump and before installing the new pump. Bubbles may also be caused by the new pump having an air leak between the pump's inlet to its attached fluid reservoir.

What do you think?

Did you put the front end in the air and turn lock to lock several times? That should have taken care of any bubbles.

I did that after I installed the new (remanufactured) pump (and both lines), while putting the return line into a clear container and adding new fluid into the pump's reservoir. I stopped adding fluid when the fluid looked clear.

Like I said earlier, I still need to check the reservoir for bubbles in the fluid before trying to purge them again.

I wonder if one of the lines got loose and allows air to leak into the fluid. But I think it would have also allowed fluid to leak out, but I didn't see any puddles underneath. I've read that air could be leaking into the loose connection between the reservoir and the pump, but they're connected together as a single unit that I bought, and may be indicative of a faulty unit. I'll try purging the system again before I remove and disassemble the unit.

start the car and you listen- if you hear it in the cab, you will hear it under hood.

get in front of the car - p/s is on pass and trans is on right --which side is it coming from? put head under hood and listen.

Personally I have very bad luck with remanufactured power steering pumps.
After a short they start to wine and make noises.
I now go to Andrew at Bonnevilles Unlimited and get the OEM ones.

To 99SSEi: I did barely just hear it in the cab, while in park, so I went out front and it seemed louder on the left side. Just to be sure it's the pump, I used a stethoscope to verify the grinding noise was coming from the pump. I'm now convinced it's from the pump and not the tranny. Thanks for your advice, otherwise I wouldn't have used my stethoscope.

To dougtoth: The remanufactured pump might be faulty, but just to make sure, I'm going to try bleeding the air out of the system again. If that works, then fine. If it doesn't work, I wonder if the air bubbles will do any damage to the rack. If they only damage the pump, then I'll just drive it until it fails and then I'll buy a brand new one to replace it.

To double check, you could take the belts off and run it long enough to see if the sound goes away.

I tried to bleed out the air from my system again, by borrowing a hand vacuum pump from Autozone and connecting it to a home-made screw-on cap placed over my P.S. reservoir. I made the cap from a used Dorman 82605 GM Power Steering Cap I bought on Amazon.com for $7.70.

It worked like a charm when I pumped the vacuum to 20 bar, and held, but my P.S. whined when I turned the wheels from side to side. When I pumped harder and faster to get it to 25 bar, the whining went away but the vacuum dropped quickly to 20 bar and P.S. continued to whine like before.

So, I must have an air leak somewhere that continues to add air bubbles to my system.

So, my next step is to do the trick found on https://www.youtube.com/watch?v=LfeVoQtJOvQ by connecting an air pump (radiator tester or tire pump) to my home-made screw-on cap (connected to the P.S. reservoir) to add a few p.s.i. of pressure to the system, and search for P.S. fluid leaks at the hoses, P.S. pump and steering rack.

I'll let you all know what I find out.

I put up with the grinding noise for quite a while, until I added Lucas power steering stop leak fluid, after removing most of the old fluid from the power steering reservoir. The stuff is awesome! It eliminated the grinding noise, and made my steering a lot easier to turn.

That's good it worked for you. I had an internal rack seal go on my wife's x-type and tried a jag version of that stop leak called out in a TSB. I wasn't as lucky. I ended up replacing the rack.