Can our coolant systems purge excess fluid?

[CERF04ZHP]

Noticed a small puddle of coolant under the front of my car on the driver's side yesterday afternoon. Its been parked in the garage since Friday afternoon, which was a "spirited" drive home from work and parked hot. So I checked the coolant level, which is perfect. Then I checked around to see where it might be coming from. I can see wet evidence all the way up almost to the tank cap. I replaced the expansion tank back in the fall. Is there a chance that I have been driving around with it overfilled this whole time, and it just decided to burp now? Or is it a truly sealed system and I have developed another leak? Possibly a cracked tank again? There was a decent amount of fluid on the ground, and in the belly pan. Strange how the float level still reads as being full.

via EVO.LTE

[BCS_ZHP]

Did you change the expansion tank cap too when you did the tank? The cap can look fine but under high pressure will let a bit of fluid vaporize past the rubber seal and then it condenses back to liquid form. The telltale sign is evidence of coolant stains around and under the cap neck, normally running down the sides of the tank. A new cap is $10 and a quick/easy cure for this problem.

[Avetiso]

When I refilled my car after the accident/repair, I was leaking fluid slowly as well, and this is on the old ET. I think it may have been excess fluid, because it stopped leaking after a while, and the level is still normal.

[CERF04ZHP]

Cool, thanks guys.


Did you change the expansion tank cap too when you did the tank?

Yes, I did replace the cap.

[telijah]

To expand on your question: no, it is not supposed to vent like other vehicles' systems. Our expansion tank is connected directly to the radiator and is supposed to handle the job of capturing excess fluid. Unlike other cars, who have a traditional "overflow" tank, which is connected to the radiator only via a small rubber hose. Excess fluid in those setups is escaped by the radiator cap having a pressure valve, and once the pressure is too high, it opens up and allows coolant to flow into the overflow tank via the little hose.