1998 sebring jxi convertible cold weather p/s noise

[L2bsing]

When it is cold outside, my 1998 sebring jxi convertible make a horrendous noise from what sounds like under the dashboard. The sound will go away after driving a few blocks. I took it to my mechanic and was told it was the power steering pump, yet after replacing the power steering pump twice it still makes a loud sound... like a squealing/buzzing sound. Any ideas on what else could be the problem?