Water Leak When Engine Not ON

What is this i know the thermostat is under here but why is it leaking when the engine is off.

Its not bad have not had to add coolant but still wondering if the plastic neck is leaking or something else.

On a 07 Taco Prerunner V6

 

Probably best just to buy a new tstat, tstat housing and the O ring.

1 clamp, 3 nuts and call it good. Probably time to do a coolant change anyways.

 

Something I’ve seen, a slight coolant leak will often not leak while the engine is running but leak as soon as it’s shut off. I’m not 100% sure why. My guess, say it’ll leak at 10.1 psi and not leak 10. While the engine is running at 10, once shut off pressure will spike slightly and leak, I’ve seen it many times. 10 psi number used just for an example.

If I get a coolant leak complaint, and the engine is hot, I don’t want to take the radiator cap off hot. So I’ll rev the engine for a couple minutes then shut it off, sometimes the leak will show. If not, I wait for it to cool for about an hour, then carefully remove the cap to pressure test it.

 

When parts heat up, they expand.
This seals the gap where it’s leaking.
It will eventually get to where it leaks all the time.
I’d do as @nd4spdbh said, change the components.

FWIW, here is the spec on the 3 nuts.

Torque:
9.0 N*m{ 92 kgf*cm , 80 in.*lbf }

 

Also, don’t get worried if the stud comes out with the nut.
It happens, either treat the stud/nut as a bolt.
Or try to separate the 2 and reinstall stud then nut.

 

always look for the pink stain to show where the leak is coming from