What's this little blue cap for?

[steve valentine]

whilst tinkering just 'tother day, I found a little blue cap, curiosity got the better of me and I removed it, there was no bang or earth shattering explosion, so now I need to know what it is

It's in the centre of this picture, like a little blue bust cap;

[Image: 198517_1780581586711_1004576529_31992546_2507220_n.jpg]

[andy-womble]

Drain cap to the thermostat housing. Hope you put it back ok otherwise the coolant will leak out of your engine when it is running.

[steve valentine]

yes I put it back

[pk7478]

Steve.
If someday you'll decide to replace coolant, this cap must be removed during pouring of new coolant into system.

[coxy]

Its for bleeding air out of the system after re filling