Oil in my coolant res. or am I just seeing things?

Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
I have a 2009 BMW 328 with 72k miles. I opened my coolant res. to see the color of my coolant since it was flushed 3 years ago at 64k miles (I am sitting at 72k miles right now) and noticed brown looking liquid. When I push the float down and look directly below the float, the liquid is blue. When I look at the back end of the res. there's that brownish-colored liquid. The Oil filter housing gasket was done around 67k miles. No oil dripping or smell from anywhere. Maybe the coolant is just dirty?

136384140_2705049813094505_5816534949449052980_n.jpg
 

mosaud1998

Thread starter
Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
Update: I just dipped a paper towel in that "Brown liquid" and the paper towel came out to be BMW OE blue coolant.
136748376_736993053906421_2718877789288982866_n.jpg
136400059_704197640263651_6805508232336674283_n.jpg
 

JHZR2

Staff member
Joined
Dec 14, 2002
Messages
46,576
Location
New Jersey
Cant tell from the pictures. A dipped towel won’t always get the oily residue.

If it is an AT vehicle, the cooler in the radiator may have been breached. You might want to look at the ATF as well.
 
Joined
Jun 1, 2015
Messages
1,272
Location
Arizona
The tell will be to look at the oil. If oil enters the coolant the coolant will also usually contaminate the oil. Pull the stick and look for any sign of milky foamy goo.

coolant additives like water wetter will turn to oily brown goo after it breaks down if that had bee added.
 

gathermewool

Site Donor
Joined
Jan 9, 2009
Messages
9,176
Location
New England
Pull the reservoir; if you can't see the oil on top (darker) compared to the coolant on the bottom (lighter), then dump it out into a clear container for a clearer view.

Again, the oil will be on top, so you shouldn't need to pour much to tell. Definitely worth a snapple from your local gas station.
 

mosaud1998

Thread starter
Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
Pull the reservoir; if you can't see the oil on top (darker) compared to the coolant on the bottom (lighter), then dump it out into a clear container for a clearer view.

Again, the oil will be on top, so you shouldn't need to pour much to tell. Definitely worth a snapple from your local gas station.
I took some coolant out with a syringe and it was blue OE bmw fluid. Maybe it’s just the reflection of something?
 

gathermewool

Site Donor
Joined
Jan 9, 2009
Messages
9,176
Location
New England
Good thinking with the syringe. If you were able to sample the entire top layer then it's likely an odd shadow or VERY light conamination.

I always shave a stock of two or three in the basement for odd things like you're experiencing, but mostly for brake and diff jobs.
 

mosaud1998

Thread starter
Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
Good thinking with the syringe. If you were able to sample the entire top layer then it's likely an odd shadow or VERY light conamination.

I always shave a stock of two or three in the basement for odd things like you're experiencing, but mostly for brake and diff jobs.
I got the entire bottom where that “brown” stuff is. I’ll go get some of the top layer right now and see what shows up
 

mosaud1998

Thread starter
Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
Good thinking with the syringe. If you were able to sample the entire top layer then it's likely an odd shadow or VERY light conamination.
I always shave a stock of two or three in the basement for odd things like you're experiencing, but mostly for brake and diff jobs.
I have a water bottle with 50/50 mixed BMW coolant and a non 50/50 Mixed BMW coolant jug in my basement. I went ahead and took some coolant from the tippy top and nada no brown weird stuff. Either way, I'll flush out the coolant in April during my oil change
 

mosaud1998

Thread starter
Joined
Nov 12, 2020
Messages
454
Location
Chicago, IL
I'm curious to see what you find on the top, which is where lighter fluids like oil would be.
The first pic is coolant from way down the bottom of the res.

second one is from the top. Same color no difference.
 

Attachments

  • FDF9579C-6164-4C56-A844-21D8CEE8537F.jpeg
    FDF9579C-6164-4C56-A844-21D8CEE8537F.jpeg
    105.3 KB · Views: 15
  • 9ADF345B-83D9-4AB9-8944-17C06E174F90.jpeg
    9ADF345B-83D9-4AB9-8944-17C06E174F90.jpeg
    76.9 KB · Views: 15
Joined
Sep 21, 2020
Messages
452
Possibly an intermittently leaking oil cooler. They do on occasion seep around gaskets and then stop, not common but does happen might explain the oil residue being on the bottom, it's old.
 
Top