Abstract: A hydraulic fluid tank for a drilling machine includes a primary chamber and a secondary chamber. The primary chamber is located entirely below the hydraulic pump of the drilling machine, and the secondary chamber is located above and in fluid communication with the primary chamber. The secondary chamber is adapted to maintain a hydraulic fluid level that is above the pump suction centerline of the drilling machine pump as the hydraulic fluid in the tank reaches its normal operating temperature during operation of the drilling machine. The secondary chamber is also sized and configured to allow for thermal expansion of hydraulic fluid in the amount of at least about 5% of the total tank volume as the hydraulic fluid in the tank reaches its normal operating temperature during operation of the drilling machine.