Expansion Tank/Water Pump Replacement, still getting "low coolant" warning

mitsitsad · 08-01-2018, 12:03 PM

2011 335i xdrive sedan

I've been fighting with this problem for the past few weeks now and I'm hoping to find a solution on here.

I received a low coolant warning and after doing some research on here looked under the hood and noticed some white spots around my expansion tank's seam. Reading that it was a common problem I ordered a new tank (Rein, not OEM, important later) that I installed with minimal issues.

A few days later the expansion tank is dry again. I cave and take it to a reputable BMW mechanic who informs me that my water pump and thermostat need to be replaced. $1100 later and it's all replaced, but the low coolant warning will not go away. I performed the bleed procedure 2 times and still nothing.

I take it back to the mechanic. He swapped the aftermarket sensor for an OEM one, but the warning still did not go away. He told me that the sensor sits in a cavity underneath the expansion tank and he suspects that the aftermarket plastic might be too thick for the sensor to read the coolant level, hence the warning.

Anyone else ever experience this? I know the 2011 expansion tank is different than the older E90s, but this seems crazy. Should i replace the expansion tank with OEM for 4 times the price of the non-oem?

08-01-2018, 12:03 PM	#1
mitsitsad New Member 3 Rep 22 Posts Drives: 2011 335i xdrive Join Date: Mar 2016 Location: NJ iTrader: (0)	Expansion Tank/Water Pump Replacement, still getting "low coolant" warning 2011 335i xdrive sedan I've been fighting with this problem for the past few weeks now and I'm hoping to find a solution on here. I received a low coolant warning and after doing some research on here looked under the hood and noticed some white spots around my expansion tank's seam. Reading that it was a common problem I ordered a new tank (Rein, not OEM, important later) that I installed with minimal issues. A few days later the expansion tank is dry again. I cave and take it to a reputable BMW mechanic who informs me that my water pump and thermostat need to be replaced. $1100 later and it's all replaced, but the low coolant warning will not go away. I performed the bleed procedure 2 times and still nothing. I take it back to the mechanic. He swapped the aftermarket sensor for an OEM one, but the warning still did not go away. He told me that the sensor sits in a cavity underneath the expansion tank and he suspects that the aftermarket plastic might be too thick for the sensor to read the coolant level, hence the warning. Anyone else ever experience this? I know the 2011 expansion tank is different than the older E90s, but this seems crazy. Should i replace the expansion tank with OEM for 4 times the price of the non-oem?
	Appreciate 0 Tweet Quote