[Jet1990]

Hi all,

to cut a long story short, been having some issues with the cooling system in the past week.

I was driving along as normal when the amber coolant light came on saying engine too warm drive moderately ( this sent the car into restricted power mode) . so i pulled over and switched engine off. I couldn't check the coolant level as there was too much pressure in the expansion tank so i left it a few minutes and it drove fine. Went about my business and the same occurred later than night - pulled over again for a few mins and the car drove fine after that.

Next morning i checked the coolant level and it was almost bone dry so i topped it up and it was fine for the next 4 days. Last night the red coolant light came on saying engine over heating followed by the amber one 5 secs later so i pulled over and turned the engine off. I entered the hidden menu on the dashboard to check coolant temp. It was showing 109 degrees C with the engine off so i switched it on and the temp went up to 119 degrees.

now at this point the fan was on for about 10 secs and when it switched off the temp immediately dropped to 85 degrees so i drove it home with the temp going back up to 105-110 but power was all there as normal.

this morning checked the coolant level again and it was more or less empty. There's visible signs of coolant spillage all over my engine cover ( might be worth noting i recently has the expansion tank hose replaced as it split so i would assume the system was bled properly but i could be wrong)

Theres also a fault code saying no communication to water pump.

Im not sure if its a dodgy temp sensor giving off false readings or if the water pump has gone.

Its a 2007 330i N53 engine with 88k on the clock. I have warranty on it in case it is the water pump but id rather not pay £250 excess if its only a sensor thats gone.

anybody had this sort of experience??

[Dormermike]

Assuming the coolant pipe didn't split due to excess pressure I'd be looking at replacing the coolant tank cap in case it's releasing pressure too early. Low pressure low boiling point.

[AndyVR]

Try and trace where the coolant exited from, check all hoses/housings/plastic unions/thermostat/water pump area, unless you can see that it was released from the expansion tank cap.

The spiky temperature readings are probably more to do with low coolant level/leak, if the temperature sensor is high up in the system it would of being measuring mainly hot air, not coolant.

[Robin330i]

Your water pump has died. Very very common issue, I did mine not so long ago, £250 on parts and half a day spent under the car.

[Jet1990]

So bmw diagnosed a water leak from the radiator. ( said they did a pressure test and it was coming from a gap that they deemed was caused by a stone chip) this no being covered by my warranty.

The water pump is showing no communications to the ecu but is apparently still working.( they want to replace this which is coveredby warranty)

So i made the decision to have them replace the pump and I'd get my Indy to do the radiator. They were meant to so the pump on Fri and me get the radiator done on Sat but the pump didn't arrive so I took the car back off them in the agreement is get the radiator done on Sat and bring the car back to them on Monday. Fast forward to sat evening. Brand new radiator in and system is all bled correctly. Took the car for a drive and boom engine too hot warning comes on and the car goes into that power restriction mode. I'm so pissed off because my gut feeling was the water pump or maybe the temp sensor. The cars been parked over night so I'm going to check if it's lost an coolant as I filled it to the brim before driving it last night. I had a visual check down the front and couldn't see any leaks so I'm clueless now as to what it could be. Can a sized water pump cause a coolant leak? I'm angry as I reckon bmw have misdiagnosed the fault which has caused me to spend quite abit of money on it.