Any time you replace an old faucet you have to take off the locking nut that holds the faucet tight to the countertop.
Delta sink faucet bonnet nut stuck.
To remove a stuck faucet nut you need a wrench or locking pliers to break the mineral deposits grip and then turn in the opposite direction.
But often that nut will be frozen due to corrosion or mineral buildup from years of water seepage.
Here are some nut freeing tricks from richard trethewey.
Remove the faucet s bonnet nut.
The easy way to access a corroded basin faucet fixing nut for removal.
The stroke by billy squier permission to use in this video by the legend hims.
Removing a stuck on bonnet nut when changing a cartridge on the delta shower valve.
The bonnet nut fits over the faucet valve and holds the valve into place.
Make sure that the surrounding area is free of any valuable items as the action to strike the motion against the plumbing nut.
Put a wrench on the fixture or nut and strike the handle sharply with a hammer to loosen the fixture.
To remove the bonnet nut turn it in a counterclockwise direction with a wrench until the nut is free from the threads on the valve then lift the nut up and over the valve to complete the removal process.