Oil or Rust in Coolant Overflow Reservoir?

[toddtat]

Hi All
First time posting. 2001 VP 7.4Gi w/FWC. Recently pulled the heat exchanger to rebuild and refilled the system with clean 50/50 coolant. Al seemed well, but after running a couple of times I noticed upon shutdown that the pristine green coolant in the plastic reservoir was no longer so pristine. Looked dirty. Upon cooling some rust colored residue settles down at the bottom of the overflow tank. I sucked some out today with a turkey baster and put in a mason jar. Having a hard time figuring out whether it is rust or oil. It settles to the bottom and separates from the coolant, and is rust colored. Is it even possible that engine oil make its way into the FW side of the system? And even if it could, seems like it would turn milky, not rust colored.

An avid DIY guy, but no expert on cooling systems and how this could happen so suddenly.

Thanks for any advice folks, much appreciated!

 

[Scott Danforth]

Was the old coolant orange? Orange and green dont mix

 

[toddtat]

Nope - Green on green.

 

[tpenfield]

Grab that turkey baster again and suck the bottom liquid out of the mason jar for closer inspection.

 

[Scott Danforth]

Nope - Green on green.

look at your manual. for 2001, the coolant should be orange, as in dexcool.

the sludge you see is most likely the result of two coolants attempting to mix. to change from one to the other, requires several flushes of the cooling system.