How do you make a part point towards your mouse along the y axis by CFraming it?

I have two parts that are held together by a weld. They're called TurretSwivel and Turret. Turret is the part that moves. I need to CFrame the weld by using something similar to the code below.

This is an example of what I have tried:

wait(1)
player = game.Players.LocalPlayer
mouse = player:GetMouse()

findCar = game.Workspace:FindFirstChild("Car"..player.Name)
if findCar then
mainGun = findCar.Barrel
weld = findCar.VehicleSeat.Weld


mouse.Move:connect(function()
		local torsoPos = findCar.TurretSwivel.Position
		local dir = (mouse.Hit.p - torsoPos).unit
		weld.C0 = CFrame.new(0,0,0) * CFrame.Angles(-math.atan2(dir.X,dir.Z) + math.pi/2, 0, 0)
end)
end

When I use this script, it works at first but soon the turret stops aiming at the mouse.

Please help answer this, thanks. And if you have any questions please ask.

If you mean something like a rotating loop, try:

local part = [Part you want to rotate]
local mousePos = mouse.Hit.p

weld.C0 = part.CFrame:inverse() * CFrame.new(part.Position, Vector3.new(mousePos.x, part.Position.y, mousePos.z)