[Roboyle]

Hi all,

Here we go, another oil level sensor thread. I find myself in a bit of a (potentially) uncomfortable situation. A few months ago I purchased a 2008 128i with about 67k miles and have since added about 2k miles.

Changing the oil was one of the first things I did. It's consistently been about 3/4 of the way between min and max since then, until 2-3 days ago, when it suddenly started reading right at the full line.

Normally I might chalk this up to a weird sensor quirk and just watch it over time (I'll still be monitoring it), but something else has gotten me concerned. Since I bought the car I've replaced some of the fluids, including the coolant. I didn't fully drain the coolant because the thermostat/pump are original and I figure they'll be going soon, so I'll do a full coolant replacement when they go and probably change some old coolant hoses as well. So for now, all I did was drain through the radiator and molest the coolant hoses to push some more out.

Since then, my coolant has been slowly leaking, from the max to min mark on the coolant level gauge over the course of a couple days. At first I thought it was just air continuing to bleed out, and while the rate of "leaking" has slowed down I believe there still is some loss. I haven't gotten under the car yet to check it, but I hope it's either the radiator petcock that's pretty beat up and needs to be replaced, or a particular coolant hose I felt that has a very brittle spot that might have cracked a bit.

Because the coolant level has been going down slowly, I'm particularly concerned about how this might relate to the oil level sensor going up. I stuck a flashlight at the coolant expansion reservoir today and didn't notice any discoloration of the coolant in there from oil, nice blue all the way down.

I haven't looked into it too much, but I think I remember reading that the oil filter housing is a potential area where coolant and oil may mix if there's a leak.

Regardless, I'm going to just continue to monitor the levels of both fluids and see what happens. If, over the next couple of weeks, the oil level sensor stays at max and doesn't go into the over-filled range I'll just chalk it up to a BMW quirk and leave it be. I'm hoping some of y'all more experienced owners will read my essay above and weigh in with y'alls thoughts. Thanks!