[matth27]

Just replaced the thermostat in my j20a after only the top hose getting hot and testing it in water and it didn't open.

I put a new thermostat in and after driving for 10 mins the top hose gets to operating temperature but the bottom hose is pretty much cold. Temp reads halfway on the gauge after about 5 minutes of driving

Any suggestions?

[want33s]

Sounds like a healthy cooling system. Top hose getting hot means the thermostat is opening.

Hot water from engine goes to radiator via top hose, flows vertically down the radiator and is cooled as it goes, cool water is then fed into engine via bottom hose to repeat the cycle.