Please help! I have a 98 Catera with 57K miles that runs great. A few months ago, the radiator light started to come on after the engine was running for 15-20 minutes. I checked the fluid and noticed some sludge, so I had the radiator flushed and refilled. The light still comes on after 15-20 minutes. I regularly check the fluid level and there are no leaks. Is this something I should worry about? If not, is there any way to get the light to stay off?