1998 Lexus GS 300 Owners Manual - Page 389

ENGINE CHECKING THE ENGINE COOLANT LEVEL 62G004-1 " 1 Reservoir cap 2 Upper line 3 Lower line Park the vehicle at a level spot and look at the see-through coolant reservoir when the engine is cool. The coolant level is satisfactory if it is between the upper and lower lines on the tank. If the level is low, add ethylene-glycol type coolant. The coolant level in the reservoir will vary with engine coolant temperature. However, if the level is on or below the lower line, add coolant to bring the level up to the upper line. Use only ethylene-glycol type coolant. It will prevent freezing and corrosion. Neither supplemental inhibitors nor additives are needed nor recommended. (For information on ethylene-glycol coolant, see also "Engine coolant selection" described below.) 376 If the coolant level drops within a short time after replenishing, there may be a leak in the system. Visually check the radiator, hoses, radiator cap, drain cock and water pump. If you can find no leak, have your Lexus dealer test the cap pressure and check for leaks in the cooling system.