My ford ranger is going through alot of antifreeze- about 100 miles and the reservour is empty. I can't find a leak anywhere. I have heat in the truck and the truck isn't overheating. The temperature gauge goes whacky when I am running out of/out of radiator fluid but it doesn't overheat. There is some kind of water trickle noise on the passenger's side by the dashboard- can't figure out what that is either and the check engine light is on. I know it needs new valve gaskets because they are leaking oil. Does the truck need a new headgasket as well?Any ideas?