2008 Toyota Highlander Owners Manual - Page 454

4-3. Do-it-yourself maintenance Engine coolant The coolant level is satisfactory if it is between the "FULL" and "LOW" lines on the reservoir when the engine is cold. Reservoir cap "FULL" "LOW" If the level is on or below the "LOW" line, add coolant up to the "FULL" line. n If the coolant level drops within a short time after replenishing Visually check the radiator, hoses, engine coolant filler cap, radiator cap, drain cock and water pump. If you cannot find a leak, have your Toyota dealer pressure test the cap and check for leaks in the cooling system. 426