your t stat might be locked shut. for the 10 bucks its worth a shot to change it.

if you fill the rad, then rev the engine rad cap off look inside for bubbles. if you got bubbles you got a bad head gasket.

and 98's have a cast elbow built on the tendioner/alt bracket. it can leak too. when you buy new elbows you need to replace the o ring on the cast one, take it off the unused new elbow.