I’m still curious exactly how the expansion tank works on the V12.
Two weeks ago, I did my 2 year changing of the coolant. I disconnected bottom radiator hose, AND removed expansion tank to give it a good clean out (it was actually not bad).
I jacked up the front end of the car, with radiator bleed port (left side) up a bit higher than right side. I also opened up the breather I had installed at top of heater hose to help get air out of the system.
I put in about 4 gallons of 50/50 mix, both filling the expansion tank and the radiator. Over the last two weeks, I’ve made sure to run heater a bit and I’ve been topping off the filler tank (at radiator), only needing to add a tiny bit now and then.
Suddenly two days ago, my low coolant light came on. I checked, and the expansion tank was empty!? Yet the level was full at main filler neck. I’ve since filled up the expansion tank. I probably added a good 1/2 gallon.
So what exactly is going on!? I have no leaks and no engine issues.