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Just did a pre-purchase inspection on a 2017 GLC 300, 55k miles. The mechanic discovered a dab of light blue ... something under the coolant cap. He is certain it is not dried coolant; he says that would turn white when it dries. The current coolant is pink.
His concern is it's possible someone preciously put in an additive to "stop leaks" in the coolant. But he can't say for certain, and it might just be something that occasionally shows up in healthy Mercedes.
Does anyone recognize this blue dot (at the tip of the wooden stick) as being something fine or dangerous?
not sure if that is a brass seal or ring around the opening BUT, if you look close it appears the ring has a little oxidation. See where it is rough looking.
metal will rust but brass oxidizes and the oxidation turns blue. it could be a deposit from that. You might want to look at that or have someone look at it
If it is that I wouldn't worry about it. Is it gummy or more like a rust in texture?
You may be onto something, pictures of brass corrosion show a similar colour. Easy to imagine someone putting impure water in the reservoir and causing a tiny amount of rust.
Unfortunately I wasn't there when it was inspected. I expect it's a rust/powder texture but don't know for sure. What would someone think if it was actually gummy?
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
