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Discussion Starter #1
Hi everyone,

I have a 2015 Forester with about 45,000 miles on it. I was taking a look under the hood and noticed a lot of whiteish/greenish spots all over the engine, but nowhere on any plastic or rubber. It’s powdery and light - light enough to almost blow right off. Can anyone tell me what it is, and if it’s anything to be concerned about? I’ve attached some pictures.

Thank you!!
 

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2017 Forester XT Premium
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552 Posts
Not that it is but coolant leak? And I have seen that on metal parts I have laying outside in my metal recycle pile, alway thought it was mold
 

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2012 XT Touring 4EAT
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It's leaking coolant, probably along the top seam between the plastic top-tank and the aluminum radiator core. It is often difficult to locate this kind of leak, but here are two suggestions:

1) to confirm that it's really a coolant leak, carefully mark the overflow bottle level, say, when the engine is cold (never started for the day). Then, keep watching to see if the level returns to that mark the following day(s). Also, watch this level when the engine is hot - it's going up, right? A properly sealing radiator / cooling system will self-purge any air, at which point the overflow bottle level will only reflect system temperature.

2) the time of greatest system pressure is when you come off the expressway after a long drive and immediately shut the engine down. Both the cooling system temperature and pressure rise significantly. So, next time you pull off the highway, pull over to the roadside or a parking area and pop the hood. Look carefully for steam or 'smoke' or other things coming from the top area of the radiator.

FWIW, your radiator has a lot of excess capacity. So, just because it's not holding full pressure (i.e. leaking) doesn't mean your engine will overheat. It probably won't overheat unless you've got an internal leak - combustion gasses escaping the cylinder(s) and entering the cooling system.
 

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Discussion Starter #5
It definitely can be described to look like mold. I sent these pics to my contact at a local subaru dealership and their service guys also said it’s normal aluminum corrosion, so I’m glad there is some confirmation from you guys.

Regarding the coolant leak: wouldn’t a leak splatter over everything under the hood? The spots in my picture are only found on the metal parts of the engine itself.
 

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2007 Forester Sports XT 4EAT
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@JeffQBP normally the white aluminum oxidation will be only on the untreated aluminum surfaces.

It's not uncommon to get mold growth in the engine compartment, especially if it's not cleaned occasionally. The dusty, wet & warm conditions can be the perfect environment for mold growth. We have this on our engines, so the plan is to some serious engine detailing over this summer! :icon_eek:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
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