Coolant dump

[tkellykbnc]

2013 X1 35i runs great for days, then will suddenly show low coolant followed by about a dump of about a gallon of coolant. Let it cool, refill and doesn’t lose a drop for days, then happens again. All looks dry on top, and 2 different mechanics (including 1 with 30+ years of Bimmer repairs) can’t find the cause. Pressure tested multiple times and it doesn’t lose a drop. The have found several small leaks and repaired them (at this point the don’t even charge me). Still, can’t really drive an otherwise great little car, since I never know when it will happen again.

Any ideas.

TK

[BRK]

Possibly and only a possible- the thermostat. Causes a surge if it fails to open correctly- too much heat in the block and out comes the water.
Had a similar issue with a Toyota Prado. Intermittent fault but (finally) noticed the temp go high then low.

[gJesus_1911]

Did you ever find the root cause of the coolant dump issue?

[SharpAndCunning]

Did you ever find out what was causing this?

[40_roll_bmw]

My car did this exact same thing the day I bought it. Dealer installed a new radiator and retuned it back to me. Happened again 20 minutes after. They replaced the radiator once again (two in a week) and so far I haven’t had this issue. But the exact same thing happened to me. It would run fine then all of a sudden it would dump all the coolant.

[gJesus_1911]

For me it was the radiator plug I believe or you might be having issues with your transmission heat exchanger since I believe it only dumps it when it’s up to temperature.

[maxwmiller]

A loose or broken hose clip is also to be suspected. Could be fine at ambient temperature but come undone at operating temp.