35i coolant loss - help?

[E84BMWguy]

I have a 2014 X! 35i w/ 33,000 miles. Yesterday when I started it a warning light appeared on the dash that looked something like (possibly) a radiator graphic. I opened the hood and found streaks of coolant overflow all down the expansion tank. No puddles or evidence of leakage under or around the car. When cool, I opened the expansion tank and could not see any coolant in the tank. The coolant level measurement in the car is not the one shown in the owner's manual and I can't tell how to read it. Also, I could not find anything in the owner's manual that referenced the warning light I had seen. I added about 1/2 quart of tap water (all I had) and started the car. The warning light did not come on and the readout for Check Control said all OK. Today I drove about 10 miles and made three stops. No warning lights or indications of problems. When I stopped the car back at the house I found water poring out of the expansion. I had driven about 100 miles immediately before the problem and now need to drive that same mileage to return home. Any advice on whether I should attempt this drive or should I just call a tow service?

This is a very unexpected development for a car that I've been taking good care of and considered a keeper. Now, not so sure.

Thanks for any help you can provide.

[Njerts]

Coolant Regulator/Thermostat ?

[fiehlsport]

Originally Posted by E84BMWguy

This is a very unexpected development for a car that I've been taking good care of and considered a keeper. Now, not so sure.

It sounds like either the cap wasn't tight, or the cap/expansion tank cracked and failed. No amount of preventative maintenance could have helped this, just a fluke failure. Replace the tank and move on - I wouldn't worry about it. Usually they crack after 100K, but it could have been a defect. Is the car still under warranty?

[E84BMWguy]

Expansion tank split at seam. BMW service advisor said it's a common failure though usually not at such low miles. Fixed and repaired under wty.