I had a large filling (2 surface) about 4 weeks ago. my tooth is still very sensitive to cold water. will this ever go away?

It should: The restoration was probably deep. Ask your dentist who knows exactly how extensive the restoration was.

Very common: A tooth may be sensitive to temperature after the routine dental treatment (filling). Most likely the reason is extensive decay in a proximity to the nerve area. Usually, the sensitivity resolves on its own within a few weeks. Rec: see your dentist if the sensitivity does not subside within a few weeks, or if your get spontaneous toothache.

See dentist: Contact the dentist. Variables include, high bite and deep restoration. Both can be addressed by your dentist. If the sensitivity is getting less, this is a positive sign.

Depends on cause: If it's a high filling a quick adjustment will bring almost immediate relief. If it was a deep cavity nerve of tooth may take time to heal, or root canal Rx may be necessary. Integrity of the filling and the tooth need to be investigated for fractures or open margines. Please have your treating Dentist reevaluate.

Yes/no: yes: text book is up to 6 months but I am a "8 week or what ever the patient presents" kind of guy. It takes 8 wks for the tooth to regenerate new dentin or to truly heal after treatment. So you have a simple window. No: if it gets worse or not better after 8 weeks it could be as simple as a filling that is high or it is irreversible and a Root canal is needed still in doubt call your dentist