Good morning all and happy holidays.

I’m working through other issues and finally have a Kdcan cable arriving today to help chase another electrical issue.

anyways, I just had the car in the shop last week for a coolant and oil leak. They are a reputable BMW repair place and replaced the oiler filter housing gasket and oiler cooler filter; then replaced the water pump and thermostat and the hose.
well last night I got a low coolant warning and let the motor cool off in my driveway. I opened the reservoir and noticed it was indeed below the low mark.
so I guess I’m wondering, does anyone have any idea what could be happening?
there IS visible coolant where my car sits overnight, and now this morning the reservoir is empty.
I looked all over the engine and coolant pipes to no avail but can def see it dripping off the bottom cover.
since they insure all their work they are asking me to bring it in this morning but I’d love to hear others thoughts.

 

I had a similar coolant reservoir leak and tracked it down using an inspection mirror.

Also, when I had my water pump and thermostat replaced, the reservoir went at the same time due to the heat.

 

Same. The coolant reservoirs are known to have hairline cracks at the base or where the sensor connects to the bottom. You can source a new one from FCP Euro for about $80. I think a new cap runs you extra. Wouldn't hurt to maybe replace it anyways since these are known failure points, but definitely see what the verdict is from the shop before you throw more money at it.