Lately i've noticed that my temp gauge has been all over the place, and bought myself a new thermostat. After putting off the thermostat replacement until last night, i found that my rad hoses are being sucked together. I ended up topping off the radiator and was on my way. Now with a full radiator it is still sucking the rad hoses together. Should i go ahead and replace the thermostat or is there something else to be looked at?