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Discussion Starter #1 (Edited)
While clearing the snow around my cobalt (NE blizzard of 2016!!!) I noticed a yellowish-greenish stain on whats left of the snow under the car. It was under the rear of the car, driver's side. I think I also saw a little directly above the stain on the underside itself. Note: I cleared the snow yesterday (Sun) but haven't run the car since Wed. Yet the drip was on the little bit of snow I didn't clear... Any thoughts? :thanks

(can't figure out how to attach a photo to show the location...)
 

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It's a chemical reaction with stainless steel. I had a car that did this. Looked for a coolant leak forever until I figured out what it was.
 

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Yeah it's the snow and the stainless. Not exactly sure how it works but it's only ever done it on one car that I've owned so it drove me nuts trying to track down what was leaking. I was online one day and a guy was complaining about the same problems and posted pictures. It was the exact same thing and another member posted a link to a site showing that it was a reaction to stainless and moisture.

---------- Post added at 07:06 AM ---------- Previous post was at 07:04 AM ----------

I drove the car I had for 2 years and never had to top up any fluids. If it helps the only fluid in your car even close is antifreeze, ac, and you don't have power steering fluid so it's not that. If your coolant stays up and your ac pipes aren't stained with refrigerant than it has to be what happened to me.
 

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Discussion Starter #5
I wound up noticing it under both of our cars. Chances of both having the same style of leak is very low. Also checked the coolant in the cobalt which appeared to be orange/red, not neon yellow. So I'm assuming your explanation is the right one :) Thanks for your help!
 

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No problem!
 

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Actually money_man:

Galvanized steel uses zinc as a rust inhibitor.

Zinc, when hot and in the presence of iron and a catalyst, creates yellow zinc oxide in the form of crystals. The connection is the catalyst - salt water - or compacted snow with road salt mixed in. If the snow is able to touch the exhaust heat shields and the exhaust pipes at the same time, the chemical reaction between the two dissimilar metals creates the bright yellow crystals.
 

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Ah good man. I was close!
 

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Discussion Starter #9
Actually money_man:

Galvanized steel uses zinc as a rust inhibitor.

Zinc, when hot and in the presence of iron and a catalyst, creates yellow zinc oxide in the form of crystals. The connection is the catalyst - salt water - or compacted snow with road salt mixed in. If the snow is able to touch the exhaust heat shields and the exhaust pipes at the same time, the chemical reaction between the two dissimilar metals creates the bright yellow crystals.
Interesting. I last drove the cobalt on Wed 1/20. Maybe Thurs 1/21. Then it sat in the unsalted driveway over the weekend when it snowed. The snow drifted under the car. Could any salt on the undercarriage (maybe from pre-treating the roads or past storms) be enough to cause this reaction?
 

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Yes, don't need much salt.
 
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