Replacing the Coolant/expansion tank on a Range Rover Sport L320 or indeed the L322 and the Discovery 3 due to a faulty sensor is a very common issue. The usual cause is not the sensor, but the float becoming porous and not reading the water level accurately, in other words sinking.
So, to solve the issue and stop the fault code constantly showing on the dash it needs replacing.
This video shows you how to replace the tank, it's the same unit on each car mentioned and although access will vary between the cars the approach to carrying out the job is very similar, so watch my warts and all attempt at the task. It's straight forward but fiddly.......

Just done the one on my L322 - it's a different shape though. Visitor from fullfatrr.com
* GONE. 2012 RR Sport HSE SDV6 Orkney Grey. Now being piloted by RRSTDV8
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Need to do mine, but struggling to find a replacement tanks, could anyone tell me the part number please? 2010 HSE TdV8 in Stornoway Grey.
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I used this
https://www.ebay.co.uk/itm/163238856842

Did mine recently for the same reason old fluid bottle never lost a drop but fed up with the warning message, new ebay bottle fitted now I seem to lose coolant

So do I, I think.
I was defo loosing coolant as got the error, I looked and the bleed valve on the edge coolant pipe was leaking, I tried to turn it and it snapped!
Managed to replace that but I think I am still loosing a small amount somewhere, that it I have airlocks clearing

I need to do mine, it never really bothered me apart from the light cause I knew it didn't loose any fluid, until I had the inlet manifold replaced. Checked the water the other day and the tank was almost bone dry. Bought a dye kit from ebay and found this. Does anyone know if its a gasket or O ring before I undo the pipe

I too have been loosing coolant since having manifold replaced, found that the top coolant hose was leaking water, just removed , dried and cleaned and refitted and think it may finally be ok.

Phil2k wrote:

I need to do mine, it never really bothered me apart from the light cause I knew it didn't loose any fluid, until I had the inlet manifold replaced. Checked the water the other day and the tank was almost bone dry. Bought a dye kit from ebay and found this. Does anyone know if its a gasket or O ring before I undo the pipe

It wasn't dye on the fuel rail, just a scratch on the sticker that showed up under the uv light

Phil2k wrote:

I need to do mine, it never really bothered me apart from the light cause I knew it didn't loose any fluid, until I had the inlet manifold replaced. Checked the water the other day and the tank was almost bone dry. Bought a dye kit from ebay and found this. Does anyone know if its a gasket or O ring before I undo the pipe

Phil2k wrote:

I need to do mine, it never really bothered me apart from the light cause I knew it didn't loose any fluid, until I had the inlet manifold replaced. Checked the water the other day and the tank was almost bone dry. Bought a dye kit from ebay and found this. Does anyone know if its a gasket or O ring before I undo the pipe