Losing coolant in an unusual way.

[bhm1712]

I'm losing coolant and I didn't know why until tonight!

I've been having to top up just a small amount each week. Tonight as soon as I parked up I popped the hood and found coolant on the subframe below the coolant bottle and the coolant bottle itself around the lid was wet and also around the bottles vent pipe.

No bubbles or excess pressure or boiling over. It's topped up to the full hot mark. Now if I depress the front suspension and bounce it a bit the coolant in the bottle sloshes out the cap and vent pipe! And spills onto the subframe. Is it ok to just ignore the marks on the bottle and maintain the level a bit lower?

Also, the bottle lid doesn't have a seal and its just a press fit so I was thinking of cutting a bit of cork sheet to size and pressing it into the lid. Do you think that will work?

[SUPERCHARGEDGTA]

you could seal the lid but make sure you dont seal the vent, the header tank is not intended to hold presure

as long as there is coolant in the bottle whrn cold even if slightly below minimum it will be fine
have you been topping up when hot or cold?
you should check it cold, as the hot mark is a maximum not a recommended level

[bhm1712]

I've been checking when hot as it says FULL HOT so I've maintained it at that level when the engine is up to temp. When it's cold the level is at the FULL COLD mark. I won't seal the vent, just the cap. It is weird for me having the bottle mounted on the inner wing! Seems an awkward place to have it as its bound to move a lot!

[SUPERCHARGEDGTA]

cant remember where mine was

[Big Chief]

all generations of F-Body have the expansion bottle on the inner wings