Can one of you guys who is much more experienced at this give me a heads-up on the airpump problem?

I've got a 1996 850 Wagon, manual, non-turbo, that has had chronic CHECK ENGINE lights since about 10,000 miles due to the air pump.

Sometimes I will reset the light and the problem will come back in a few days. Other times it will be reset and stay that way for many months. In the past few weeks it has been re-occurring.

Several of the mechanics I have talked to say the problem is "moisture" in the pump and that the only solution is replacement of the pump ($300-$500).

What is really happening? I've read some posts here that say that when the pump is removed, water "flows" from the pump's output hose--sounds like the problem is more than just a little moisture.

So what is really happening here? Is the valve that sits on top of the exhaust manifold not closing when the pump stops injecting? If this is happening, is the valve allowing moist combustion gases to condense and accumulate in the hose between the low-positioned pump and the valve. If this scenario is true, can I replace the valve and solve the problem? Can I pull the pump, take it apart, clean it up, and get it going again?

Assuming I can get the air pump situation fixed, I'll just schedule to take the pump apart and clean it every 10,000 miles and, if I find moisture in the pump, I'll replace the valve.

What do you think?