Brown Milkshake On Top Of Raditor


Active Member
Oct 1, 2005
Cleveland, TN
Found this in my radiator yesterday morning and I immediately thought of oil in my coolant, but my engine oil on the dipstick and under the cap is perfect. If I get the milkshake on my finger and swirl it around, it dries up and turns to dust. I'm just looking for an opinion. Is this rust or oil?

BTW, the car has brand new head gaskets and new Trick Flow heads
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thats not what oil in the coolant looks like when Ive had oil in the coolant.

did you mix orange and green coolant? oil certainly wouldnt dry up and turn to powder.
Just looks like some brown sludge.
Clean the system really good. Not going to be easy and is certainly going to be time consuming.
IMO, take the radiator completely out of the car. You will be shocked at how long it takes before clean water comes out the other end.
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I've been running rusty old coolant in the car for over 2 years until I swapped my new Trick Flow top end kit on (which was 2 weeks ago). I flushed the entire system with the the water neck off the intake until I saw clean water circulate. I filled and bled the cooling system with fresh 50/50 mix, and everything looked clear. So I put the cap on and forgot it for a week until yesterday.

I'm thinking running the car hard with a closed cooling system loosened up more rust in the passages? Is that a possibility?