What Causes High Transmission Oil Temperature in Corolla?
2 Answers
Corolla transmission oil temperature may be high due to either excessive or insufficient transmission fluid level, or a damaged transmission pump. Excessive or insufficient transmission fluid level: Check the oil quantity in the transmission oil pan and adjust the transmission fluid to the specified level. The correct procedure is to park the vehicle on level ground, place the gear shift lever in neutral and lock it. First loosen the oil plug to check if oil leaks out. If excessive oil flows out, drain some of it; if no oil flows out, the level is too low and hydraulic transmission fluid should be added until oil begins to flow. Damaged transmission pump: The transmission pump controls the distribution of high-pressure oil from the torque converter through the transmission distribution valve to the second shaft assembly to achieve forward and reverse movement of the vehicle. A damaged transmission pump will cause poor oil supply to the transmission. With prolonged use of the vehicle, increased wear can lead to internal leakage in the transmission pump, causing transmission pressure and mechanical efficiency to fall below requirements. This results in poor oil supply in the suction line, inadequate lubrication of moving parts, increased friction, and system overheating. It should be noted that air leaks or blockages in the transmission pump suction line can also cause insufficient flow, leading to excessively high oil temperature.
After driving a Corolla for so many years, I believe high transmission fluid temperature is mostly caused by insufficient fluid level or deteriorated fluid quality. If the oil level is too low, excessive gear friction generates heat; if the oil is too old, its viscosity deteriorates, reducing cooling efficiency. Another example is a clogged transmission cooler where dust accumulation affects cooling, making it prone to issues during long summer drives. I've personally encountered this situation and learned to avoid sudden acceleration or prolonged uphill driving. Under high temperatures, internal transmission components may burn out, leading to costly repairs and safety hazards. Regular fluid level checks and timely replacement with quality oil can prevent minor issues from escalating into major problems.
