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Causes of Excessive Oil Temperature in a Torque Converter
Release date:
2022-05-10 14:43
Source:
Dana torque converter Excessively high operating oil temperature is a common malfunction. When this occurs, the loader becomes inoperable. Moreover, elevated oil temperatures accelerate the oxidation and foaming of hydraulic fluid, compromising its lubricating properties for moving components, leading to seal degradation and impairing the machine’s normal operation. Based on practical examples, this paper provides a detailed analysis of the causes underlying several such failures and proposes corresponding corrective measures.
After the overhaul, a certain loader was used to place ballast inside the culvert. Within less than a month of operation, it was observed that the torque converter–transmission system, when running continuously for half an hour, … Dana torque converter The oil temperature display has reached 120°C, and the bucket noticeably lacks power. At this point, the transmission oil pressure gauge reads 1.1 MPa, indicating that the transmission oil pressure is normal. To accurately identify the root cause of the issue, we started with the transmission oil cooler and systematically investigated all potential factors that could be contributing to the torque converter’s temperature rise.
1. Dana torque converter and the components of the transmission hydraulic system and its cooling principle
The heat generated during the operation of the torque converter and transmission is primarily dissipated through the circulation of transmission fluid. As shown in the figure, the transmission gear pump draws oil from the transmission oil pan via a hose and filter; after filtration, the oil flows to the pressure‑regulating valve (1.1–1.6 MPa). From there, the pressurized oil splits into two paths: one path passes through the clutch cut‑off valve into the transmission control distribution valve, and then, depending on the position of the shift valve spool, enters the I‑gear, II‑gear, and reverse‑gear hydraulic cylinders to engage the respective gears; the other path flows through embedded pipes in the housing wall into… Dana torque converter Then, the oil exits the torque converter and flows through a hose to the radiator. After being cooled by the radiator, the low-pressure oil lubricates the transmission’s overrunning clutch and planetary gear set before returning to the oil pan. This valve regulates the torque converter inlet pressure at 0.4 to 0.55 MPa and the outlet pressure at 0.3 to 0.45 MPa. Heat dissipation from the transmission fluid is achieved primarily through air cooling via the radiator, as well as natural heat loss during flow within the housing.
2. Several factors that cause the torque converter oil temperature to rise excessively
2.1 Insufficient inlet pressure of the system
According to Dana torque converter - The cooling principle of the transmission system: the transmission pump draws working fluid from the transmission oil pan, which then passes through a pressure‑regulating valve. One flow path goes to the torque converter, where it is cooled by the radiator before returning to the oil pan. The other flow path enters the transmission itself. If the system’s inlet oil pressure is insufficient, the oil pressure supplied to the torque converter will be too low, resulting in inadequate oil flow and insufficient oil reaching the cooler. Consequently, the oil cannot be adequately cooled, causing the oil temperature to rise rapidly and leading to excessive transmission temperatures. There are several primary causes for insufficient system inlet oil pressure:
(1) Improper system pressure. The pressure regulator is a critical component of the hydraulic transmission system, controlling the pressure of the working fluid entering the system. If the spool of the pressure regulator is worn and leaking, or… Dana torque converter If the pressure valve fails or becomes stuck and can no longer regulate pressure, it will result in insufficient oil supply and a drop in torque converter pressure.
(2) Wear of the variable‑displacement pump increases the clearance between the gears and the end cover, leading to severe leakage and insufficient oil supply. If the system pressure is too low, the oil flow entering the torque converter will be inadequate. Additionally, if the pump’s suction line leaks or the oil level in the oil pan is too low, the pump may draw in air, also resulting in insufficient oil delivery.
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