Honda CR-V (2.0 petrol R20a) overheating - suggestions?

[Flatlands]

Hi,
We’ve a 2008, 2.0 (R20a) petrol CR-V with 190,000 on the clock.
It’s overheating - the bottom hose is cold and the radiator is cold at the bottom too. The top hose is hot.
I’ve:
changed the thermostat (no difference)
checked the old thermostat in hot water (it still worked)
removed the new thermostat and run the car with water and the bottom hose heated up
partially drained the system and added Wynns radiator flush - that produced some bits of rust when drained

On the initial drain of the system to change the thermostat I did notice a cloud of brown water. There’s also some deposits around the hose connectors and thermostat housing - it’s reasonably hard and crumbly - could it be limescale? The can hasn’t always had the correct antifreeze mix as it had a slight leak a few years back and (as it turns out) was only topped up with tap water.
Additionally, I replaced the radiator just over two years ago (because of the slight leak) and the system has been fine since.
Due to the mileage of the car, I didn’t want to take it to a garage but I’m fresh out of ideas - all thoughts gratefully received!
Thanks

 

[Burnerman]

Have you considered the water pump may have failed, i.e the impeller may have dropped off the back of the drive pulley?
The crusts you mention are more likely to be historic antifreeze seepage, courtesy of those ghastly spring hose clips used these days!
John

 

[sxturbo]

Failed water pump, is the most likely cause, and you aren't getting circulation.

The top hose is hot because the thermostat opens and the water boils out the head

 

[Flatlands]

Thanks for the replies - when I ran it without the thermostat, the bottom hose heated up after the top hose was warm and the engine never overheated - it stayed below normal. I’d have thought it wouldn’t have done that if the pump was defective?
Also, it looks like the access to the pump isn’t the easiest, so not a job that I’d be undertaking

 

[Mottie]

Thanks for the replies - when I ran it without the thermostat, the bottom hose heated up after the top hose was warm and the engine never overheated - it stayed below normal.

Convection. That’s how cooling systems worked on old cars that didn’t have water pumps. Sort of like a gravity hot water system. Check the pump impeller as others have said.