I have a 2001 landrover Discovery II. I hear water in the dash and it’s making a swishing noise. I’ve done a pressure test and there aren’t any leaks. Any other suggestions?
I would bet the coolant level is low, or there is air in the cooling system.
I had a 1991 Cavalier that had that kind of sound. I would check the tray in front of the firewall, where water runs in off of your windshield. It should have little rubber flaps to let water out ,but these can become clogged with pine needles or leaves, leaving what is essentially a basin of water under your hood, by the windshield. When you drive, you would hear it slosh around.
It is probably moisture condensation on your A/C condenser. There is a drain tube on your firewall that is probably clogged. Find it, pull it off, and clean it. You probably also need to clear the drain through the firewall that the rubber drain tube attaches to. Find a blunt, thin tool like a nail punch that you can push through the firewall drain. Don’t push too hard or you might damage the condenser.
I still bet it is low coolant or air in system.