97 WRX

I cant figure it out. Im losing a header tank ever 70 or 80 miles ish. There are some water marks around the thermostat housing but not enough to justify the amount Im losing.

Also, if I leave the car on tick over for ages it doesnt appear to lose anything and the fan works fine. Its only when Im driving it. The heaters all work fine as well, no steam inside etc.

 

Crack in the plastic end of the rad perhaps?

 

Wouldnt it drip though as I left it on tick over? Left it up on a ramp for an hour earlier and its as dry as a bone.

 

Coming out of the rad cap on load?

 

Does the expansion bottle level go up and down a lot?

 

hate to say but does it get hot?, head gaskets, check your oil filler cap for a cream looking sludge (waster and oil mixing together)

 

Is the cap tight enough? I was losing water and found the cap was a bit slack. steam was escaping under load, hense the water going down.
I bent the tabs a bit on the cap and it seemed to solve it.
Worth a try.