Hey guys,
I need some help...I have 2 questions
My girlfriend just bought a 00 integra gs and she's having some problems with her temp. Gauge...when she let's it idle it goes up to a little below normal temp. But as soon as she hits the gas and starts to accelerate the needle goes all the way down to cold, it doesn't go back up til she let's the car sit and idle, another symptom is when she turns the heat on it only blasts luke warm if that, never hot. I think it may just be an issue with her thermostat and that's a cheap 15 dollar fix but I'm not positive...

And on my 00 civic si only in the winter when I'm cruising on a road with a lot of hills my temp. Gauge will shoot almost all the way up to hot when I'm going down a hill and not touching the gas pedal, just drifting down a hill...I don't know what would cause that neither, I was also thinking a thermostat issue

Thanks in advance for all of your help!!
Would like to get both of these issues fixed saturday!