Thanks so much for your response. I intially thought it might be alternator or water pump bearing but it kind of changes pitch occasionally like a fan motor so i thought it might be the blower motor but turning it off made no difference. It has 150000 on it none of these things have been replaced since new so it could be any of these things, but im leaning towards the thermostatically controlled fan or alternator. Havent really been able to get out and check it good its been so rainy and cold here .