Temp warning light flashing but engine seems ok - Any ideas?

[kevtherev]

Cant seem to disconnect wire connector.

Does it just pull off, or do I need to release any clips?

Don't want to pull too hard, just in case there is something else that needs to be released first.

Also, now I've started twisting and pulling, water is dripping from sender housing. Is that to be expected?

Ok
In a word no
The old o ring is now leaking.
You may find it easier to find the red/yellow wire in the junction box (top left of the engine bay) and pull the connector apart, you're achieving the same result

[tobyn]

Good thinking!

I disconnected the lead in the engine bay and temp gauge fault dissapears, so looks like sender unit or associated wiring is the problem.

Is changing the sender unit an easy job?

Do I need to drain the water first and then refill, bleed, pressurise etc.

I only have basic tools, but I have a reasonable mechanical mind and skill set.

Garage or DIY job??

[clift_d]

If you get everything ready and to hand you can just loosen off the old sender, quickly remove it and put your thumb over the hole while you get the new one, then quickly remove your thumb and fit and screw in the new sender, and tighten up. You'll lose a little bit of coolant but no need to drain the system. Then just top up the expansion tank again to the brim.

[marlinowner]

I'm sure this is an unnecessary warning, but....
Cold engine for changing the sender, relieve any pressure in the system by cracking the dalek cap on the expansion tank.

[marlinowner]

When I say "cracking"...

[tobyn]

Got it.

Will give it a go.

Thanks for all the advice.