How far do I trust my coolant temperature gauge?

Many BMWs will read exactly central on the temp gauge if the actual coolant temp is within the limits of the normal operating temperatures. So more like an idiot light. Once it goes outside those limits it will read either high or low. It is possible on some to make the dash read the actual temperature. A Google on your model should give details.

Does the heater work normally on a cold day? If so it's likely the coolant temp is fine.

Thanks for the prompt reply. Since topping up and bleeding the coolant the heater is working better/quicker than I remember before. I'm wondering if I've developed a slight water leak and not having had one before I've got a bit slack on checking my coolant level. Plus I've probably never compared the temperature of top and bottom hoses by touch before. I'll check out the temperature dash display as well.

ar Parts) and the coolant level sensor was a sloppy fit on the threads so l= eft the blanking cap on. Recently discovered I was low on coolant. Topped u= p, bled, topped up until I'm pretty sure I've got no air locks but........ = After a run top hose is too hot to touch for more than a second while the b= ottom hose is barely warm but temperature gauge never moves above the point= it always has sat at. First thought was thermostat stuck closed but wouldn= 't that send the temperature gauge high? I know it sounds lazy but reluctan= t to change the thermostat in this weather if I don't need to. Can I trust = the temperature sensor? Regards.

Most car temperature gauges are as reliable as an ASDA special offer.