Just fixed the a/c on my car and while i was charging it i noticed this :

 

It could be a number of things but an overfilled expansion tank could be culprit.
The tank is part of the pressurized system and not an overflow tank.

When cold the coolant level should not be higher than the minimum mark,
leaving adequate room for expansion, or just to the top of the fins in the bottom of the tank.

Hope this helps...

 

well i just overfilled it thinking something was wrong, but i havent ever messed with it before. Maybe the mechanic topped it off when i got my spark plug re-threaded...

Thanks for the info. The "temp" gauge on the car hasnt ever budged but i havent driven it rough yet.

 

not to worry you BUT


Maybe the mechanic .... when i got my spark plug re-threaded ....

uggggggg

as we used to say in my office:
the window of opportunity is WIDE open

 

These tanks are not like old tanks that don't do anything except hold extra coolant for when the radiator cools. They are pressurized when the system is hot. It looks like maybe the cap wasn't tight (or is bad) and it spews when hot. (Who doesn't?)

 

Is this the first time it happened? Looking at the video, the expansion tank shows some old, dry stains from the cap. The expansion tanks are known to leak in our cars (especially from the cap). Mine has been doing it for almost 30Kmiles. I just kept an eye on the coolant levels and finally had it replaced when the thermostat was replaced last week. One less thing to check (at least not as often as before) when the bonnet is open :D

 

im sure its not the first time, but its the first time ive noticed. my car seems to be running fine though so i wont sweat it to much. Thanks