Circuit/System Description

WARNING: This page is about a different car, the 2019 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.

The primary source of heat in the 5ET50 transmission is the drive motors. The drive motors are cooled by the transmission fluid. Hot fluid exits the drive motors and flows to the transmission oil cooler through the transmission cooler supply line and thermal bypass valve. The thermal bypass valve assembly is located near the lower left side of the radiator. The cooled fluid returns to the transmission through the transmission fluid cooler pipe assembly and cools the control solenoid assembly. The transmission fluid temperature sensor is located in the control solenoid assembly and is not serviced separately. The Transmission Fluid Temperature parameter on the scan tool should rise steadily to a normal operating temperature, and then stabilize.

The thermal bypass valve is mechanically operated, based on the oil temperature of the transmission in order to maintain optimum transmission operating efficiency. The valve has an activating temperature of 82°C (176°F), with the range to move being 78 - 83°C (172 - 181°F). The full open temperature is 96°C (205°F). The thermal bypass valve assembly begins to open at 82°C (176°F) for optimum transmission operation and fuel economy. The valve has a typical oil flow rate of 9 - 10 lpm (2.4 - 2.6 gpm).

Cold Mode:

82°C (176°F) and below the thermal bypass valve bypasses the oil going to the cooler and sends the fluid back to the transmission.

Mixing Mode:

82 - 96°C (176 - 205°F) the thermal bypass valve is in mixing mode - some of the fluid flows back to the trans and some flows through the transmission oil cooler.

Hot Mode:

Above 96°C (205°F) The thermal bypass valve is fully open and transmission oil flows through the cooler then back to the transmission.