92 Accord Power Steering problem

My son's 92 Accord (2.2) burps up power steering fluid on start-up- we top it up, then bleed it until no air bubbles are present. It works fine until the next intial start-up. No leaks that we can see. It seems that the reservoir is being pressurized- anyone run into this?

Thanks.

You only fill to the "Full Cold" mark when refilling?

Actually, the level was in between the two lines- is it that sensitive to being overfilled?

Shouldn't be...usually they only barf if the wheel is turned fast with the engine off...or if there is a problem with the spool valves in the rack...

Does it ever bind when cold?

Doesn't bind, but the rack is a rebuilt- hmmm....

Turned out to be the PS pump- put in a used pump for $60.

Was there a power valve in the pump that was stuck or something?

We pulled the valve out first- although it moved in and out of the bore ok, at the bottom of the bore (pump housing) it was gouged, like the valve had been slamming into it. The problem occured only at start-up, the colder the weather, the worse it was. I was thinking maybe a sticky vane, but then there would be no pressure? WE didn't take the old pump apart (yet). It was a $60 and one hour gamble, vs. rack replacment. It's about time we won one.