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Discussion Starter #1
2012 Mazda 3 Skyactiv. I recently noticed a coolant smell and found coolant dripping from the bottom of the thermostat housing. I had replaced the thermostat about a year and a half ago but this drop just started recently. I replaced the thermostat housing this weekend but the drip is still happening. It just seems to be coming from the bottom screw of the housing.
Has anyone else had this or have any ideas?
 

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Was the engine surface the housing mated to OK? I always use Permatex Aviation sealant No3 when I reassemble thermostats.
 

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Discussion Starter #3
The surface seemed fine. Cleaned up a little bit of build up from where it was dripping but didn't see anything anywhere else on the surface. The original housing didn't have any kind of sealant or gasket, which seems odd. It's just plastic mounted flat against the metal of the engine held on by 3 screws in a Y shape.
 

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Maybe try wiping it down and trying to determine exactly where the drip is originating, Sprinkle talcum powder on the assembly if necessary.

Are you sure your model didn't have a D shaped o ring under the housing? It might be missing or jammed.

Personally I would not try to reassemble any component to an old block without sealant unless there were very compelling reasons not to. I can't see any compelling reasons for a thermostat housing. And when I tighten the housing bolts down I do it evenly - like a cylinder head.
 

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Discussion Starter #5
Maybe try wiping it down and trying to determine exactly where the drip is originating, Sprinkle talcum powder on the assembly if necessary.

Are you sure your model didn't have a D shaped o ring under the housing? It might be missing or jammed.

Personally I would not try to reassemble any component to an old block without sealant unless there were very compelling reasons not to. I can't see any compelling reasons for a thermostat housing. And when I tighten the housing bolts down I do it evenly - like a cylinder head.
I wiped it down and tightened them evenly. I looked up parts diagrams before doing it to make sure I wasn't missing something, but nothing shows a gasket. And my only "compelling" reason for not using sealant is that it didn't have any before (came right off and there was no residue or anything).
 

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Discussion Starter #8
It didn't seem to be leaking through the thermostat gasket. And with the Skyavtiv, it should almost be called a thermostat "cover" instead of a housing because it just goes over the thermostat instead of the thermostat sitting inside it.
 

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Isn't this the part?
That's exactly what the ones I bought for two Gen1 cars looked like. Mine had gaskets (rubber o-ring), and I would be shocked if they don't have a gasket because the torque spec is not very tight, only 7 ft-lbs! No gasket means you must use Permatex Blue or other sealant.

[email protected], did you buy an OEM thermostat? The attached clip from the Gen1 factory shop manual shows a gasket.
 

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Discussion Starter #12
Isn't this the part?
Sorry for taking so long to reply. Very busy couple of weeks.

That's the part for the regular 2.5L engine I believe. For the 2.0L Skyactiv it's different.

I've tried attaching a pic of the Skyactiv part with this post. First time trying, so hopefully it shows up ok.
 

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