Please help with ACC Noise on 530i

Hi- I just had my ACC Monovalve replaced on my 94 530i due to a high pitched noise during the first 15 minutes of driving my car. It did not stop the noise and not sure what to try next. The noise is present with just the ignition on or with the engine running and appears to be coming from waterpump area. If I turn the temp dials to cold, it still makes the noise?
Any ideas? Thanks everyone!!
Sheryl