lets see...my 7th gen civic lx seems to go through quite a bit of coolant for some reason.i dont know why either.there is absolutely no leaks that are visible.i had a shop check it out also...the thing about it is that my coolant resivouir cap im guessing has been blow off 2 times...i've gone through 2 of them already.i'm like where are they going?but they'll be on and then bam there gone....my question is do you think its a head gasket problem?i use to get about 330 miles to each tank of gas and now i get about 275 miles...maybe 280 max...please give me info...i've done tons of searches and cant seem to find anything that helps...let me know

 

i just had that exact same problem. a new thermostat fixed it

 

really...what about your gas mileage?did that go up?