Disco 2 Disco's heater playing silly beggars

So. Messing about with my disco this morning I thought I'd try the heater. Which has me baffled. I can't take it down the road yet as I'm still sorting it for the MOT so I had it running for a while. The temp gauge only goes between 1/4 and 1/2 when normally I'm sure it should sit at 1/2. Also the heater does feel scorching hot. Could this be because I'm stationary, could this be it needs a thermostat or could it be something worse.
One thing it seems is it gets warmer in the cab if I rev it. So could it be a water pump.
I'm in your hands.

have you removed the bleed screw in top hose and filled the system till coolant flows from it

If you dont have tester to read the coolant temp then simply replace the temp sensor to rule it out cos that gauge behaviour is odd as it should stay aroung 1/4 between 40-70*C temp reading then at 70 rise to half but i observed that between 60-70 it has an intermediar position but in normal conditions doesnt stay there for long.... dont buy very cheap britpart or allmakes get lucas or bosch(ERR2081)

The Td5 does run quite cool and at idle may not be generating enough heat to go up to 1/2 and stay there....

Mine lost heat after prolonged tickover but warmed up again after driving and as far as I know there was nothing wrong. I could drive until temp gauge was on the half way point, idle for 15 mins and it would go down to nearly cold. Drive again and it went back to normal so I don't think you have a problem.

Yorkie57 said:

Mine lost heat after prolonged tickover but warmed up again after driving and as far as I know there was nothing wrong. I could drive until temp gauge was on the half way point, idle for 15 mins and it would go down to nearly cold. Drive again and it went back to normal so I don't think you have a problem.

Click to expand...

in this case IMO even you have a problem... the gauge is managed by the engine ECU based on ECT sensor inputs so if it once was at the middle it means the ECT input was above 70*C and if it goes down below 1/4 of scale after that it means that the ECT input dropped below 40*C....so if you think that's normal i can't say more just that the cooling system was conceived as to keep the coolant temp as constant as possible once normal running temp was reached and that's around 90*C... can be stuck closed thermostat corroborated with stuck locked viscous fan or ECT sensor missbehaviour but what you describe is not normal whatsoever

Thanks for all your answers. I bled the system and had a fair amount of air in it, but she still sat at 1/4 on the gauge so I booked it in for an mot. I knew she would fail but it gave me a chance to drive her and see what it felt like on the road and what needs doing for the mot. Seems like the garage who failed it last time were after some work. Half the stuff they failed it on was fine but we found some other bits they had missed. Still at least I know what needs doing for sure. Anyway I'm drifting away from the fact that whilst driving over to the mot place the temp gauge sat lovely at half way and the heater was red hot so that's something off the huge list