Not sure how common it is but I just had mine replaced on my 1997 1.8L Sidekick Sport. The easy way to tell is check the tailpipe smoke. If it is white that's water steaming out. Take out the plugs one at a time if one or two plugs looks cleaner than the rest they are getting steam cleaned by the water leaking in. Look at the tops of all pistons w/plugs out, if one or two are shiny or not carboned up they are also getting steam cleaned. If you are losing water from the radiator that could be the problem. The best way to tell is have it dye checked. The radiator cap is removed and a special tool is used to suck up gas from the coolant, if the dye changes color there is exhaust gas escaping, thus leaky head!!! Depending on if the head is warped or not it will cost any where from 400-1200 bucks depending on how much other stuff you want to change once the head is off(timing gears, chains, belts, seals, gaskets, etc.) They are not too bad to do yourself just make sure you have the head planed to insure it's flat and checked for leaks. I hope this helped. Mine only cost $350 but my bro-in-law is a GM mechanic and changed everything you would want to with the head off. GOOD LUCK!!
