When I first start my 1998 GMC Sierra (1500)-I hear a sewing machine/noise -it goes away after about three minutes and I have noticed a lsow leak in the antifreeze

what could this be??

Does the noise come from the glove box area? If so, you probably have an intake gasket leak causing air to get into the cooling system. The intake gaskets are prone to leak on the 96-99 vortec engines.

//2000CAYukon