Power steering pump cavitation

[JohnnyL]

I have 74 chev C-10 with a power steering pump that cavitates when it feels like it. I believe it's cavitation. It's that BB's in a tin can sound. I was not getting any air bubbles so I thought maybe it was the pump bearing and replaced the pump. It was fine for a few days and then began cavitating radically only to quiet down a few days latter.

When I replaced the pump, I followed the priming and air bleeding prodedures. I even went as far as putting a vacuum pump on the filler nozzle to get air out. This was a month ago and the system hasn't leaked a drop of fluid since. I am stumped. It's running silent right now but will probably start making a racket again tomorrow. LOL...I do not know the internals of the power steering box and pump and wonder if anyone knows what I should be looking at.

[J-Ri]

I have never heard a "BBs in tin can" sound from a P/S pump. Usually cavitation would cause a loud whining noise, but only if air was somehow pulled into the pump (low fluid, engine running while upsidedown ). Are you sure the sound is coming from the pump? Use a long screwdriver as a stethescope and listen to stuff around the pump. It may be a vibration from something else. If it is the pump, try flushing out all the old fluid and refilling with new. If it still does it then, add some limited slip oil additive (about 4 oz). That will usually quiet a whining pump.

[JohnnyL]

I used a stethoscope and it comes from the pump. I've also disconnected the belt from the pump and the noise goes away imediately. The cavitation sound I refer to is common with power steering pumps when air is induced. It's not a whine.