My wife has an 02Disco with 80K miles. 4 weeks ago I replaced the water pump after it failed. I jumped in it yesterday and noticed the heater wasn't working and the temp gauge shot up after about 5 minutes of driving. When I looked the coolant expansion tank was empty. I undid the top and the tank filled up again about 2/3rds full. I filled the tank to the correct level and just went for a drive around the block. when I checked the expansion tank again the level was low until I undid the top again. Once the engine has cooled down I'll check the spark plugs for wetness and plan to drain the oil out to see if it has coolant in it.....is it possible a sleeve has dropped or is there a blockage in the sytem?
Any help would be greatly appreciated

 

Did you fill it properly after you put the water pump on?
If you overheated it you may have dropped a sleeve, but that doesnt explain the coolant lose.
Open the oil filler tube and lookunder the cap, is it white? Pull the dipstick, is it white around the top?
What coolant did you put back in after you replaced the water pump?

 

By your post, you don't know how to fill and bleed the air from your Rover.
Pm me your tele number and I will walk you thru this.
Do not drive it in the condition it is in now or you will over heat your engine.

 

Followed the instructions on the rave cd when I filled it. Lifted the expansion box to get the air out. Used a 50/50 dexcool/water mix. Checked the oil fill cap and dipstick and both look clean. Just changed the oil and looks fine.
Could it be a blocked or faulty thermostat?
When the pump failed I put some radweld in the system to make sure I got home...could this have caused a blockage? Just started the truck after the oil change and noticed the top hoses get warm but the bottom one from the radiator is cold.

 

Sounds like you need to flush your entire cooling system. Radiator stop leak will clog a dirty radiator everytime.
The lower hose wont get hot after only a few minutes and it isint supposed to be as hot as the top hose.
I would start with the coolant flush, DexCool is NOT compatable with anything other than DexCool. It will react with the stop leak and cause problems.
A blockage will not cause a low coolant level.
Once you have flushed the system then we can walk you through the proper way to bleed the cooling system. If you have a big air pocket when it comes out you will be low on coolant. I think that is your problem but my first concern is the stop leak.