E46 318ci coolant light

[TROOPER88]

Hi Chaps
This morning I picked up a 2004 310ci just to act as a bit of a run around.

The coolant temperature light is on yet the coolant level is good and the car does not overheat, the temp needle sits in the middle.

There is no white mayo on the filler cap and the car seems to drive very well.

What is the most likely cause for the light being on?:

Coolant temp sensor?

Is there also a coolant bottle sensor?

Cheers

[rayyan171]

Can be the thermostat. However, being an E46, I recommend at the very least changing the water pump anyway.

[Touring442]

There is a sensor in the base of the expansion tank. It fits into a dry chamber so it can easily be removed without coolant loss. However, it reads a float in the main tank and this can fall off inside, leaving the sensor with nothing to sense - light on. An ECP sensor is about 12 quid, the best quality expansion tank that actually fits comes from BMW and is 80+ quid. I've tried Meyle and EIS ones and they're ste.

If it's a banger and you're not fussed, pull the plug off the sensor and bridge the wires with a paper clip. That puts the light out.

[TROOPER88]

Touring442 said:

There is a sensor in the base of the expansion tank. It fits into a dry chamber so it can easily be removed without coolant loss. However, it reads a float in the main tank and this can fall off inside, leaving the sensor with nothing to sense - light on. An ECP sensor is about 12 quid, the best quality expansion tank that actually fits comes from BMW and is 80+ quid. I've tried Meyle and EIS ones and they're ste.

If it's a banger and you're not fussed, pull the plug off the sensor and bridge the wires with a paper clip. That puts the light out.

Brilliant, cheers.

So the one at the base of the expansion tank is 'dry' can be removed with no fluid loss, that's cool, I think this may be the issue.

if the float was the issue, surely the light would be on all the time?

As it is, it does not come on until the car has been running for a few minutes