Coolant pressurized overnight

O.k. so I got an 06 Honda Element with the 2.4 engine. I drove it about 120 miles the other night and everything went beautifully. I let it sit about a day give or take a few hours so I decide to do a fluid check, everything checked out o.k. except when I took the radiator cap off, a little coolant overflowed out, not much at all and no hiss or air sound, but looked to have Some pressure behind it, very little though. Some vehicle specifics and related info:
112,600 miles
Engine temp runs perfect, always has
Coolant and oil looks good, levels look good so far.
I did notice a very small leak on the resovoir.
Some water comes out the exhaust, but nothing I would consider abnormal.
I did change the air intake filter and accidentally unhooked a coolant line.

Other then that, nothing to note. So is a a little pressure in the coolant system abnormal? Thoughts?

It means your radiator cap is doing a very good job of holding pressure.


That seems pretty normal. On my Corolla sometimes it feels like there is a little bit of a vacuum, and sometimes it feels like it is pressurized a little.

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Perfectly normal. Nothing to worry about.

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I think normal. The pressure, often about 15 PSI, slightly expands the rubber hoses. When you relieve that pressure by removing the cap, the hoses relax and the fluid rises at the radiator neck. Please collect spilled coolant and dispose of properly - it is poisonous to animals that might drink it.

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