A vehicle comprising: a driveline retarder; a sensor coupled to the driveline retarder and configured to measure temperature data that is indicative of a temperature of the driveline retarder; and a coolant diverter system including: a coolant diverter body (101, 601, 701) having a coolant inlet opening (102, 602, 702, 808), a driveline retarder outlet opening (104, 604, 704, 809) and a bypass outlet opening; a valve (106, 606, 706, 806) positioned in the coolant diverter body (101, 601, 701), the valve (106, 606, 706, 806) configured in a first valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) in isolation from the bypass outlet opening, the valve (106, 606, 706, 806) configured in a second valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) and the bypass outlet opening; and a valve controller (402, 805) electrically coupled to the sensor, configured to receive operation data regarding the driveline retarder, the operation data comprising the temperature data and configured to selectively place the valve (106, 606, 706, 806) in the second configuration in response to the operation data indicating that a braking event in which a pedal of the vehicle is depressed for more than a nominal amount of time and the temperature of the driveline retarder being below a predetermined temperature threshold. a driveline retarder; a sensor coupled to the driveline retarder and configured to measure temperature data that is indicative of a temperature of the driveline retarder; and a coolant diverter system including: a coolant diverter body (101, 601, 701) having a coolant inlet opening (102, 602, 702, 808), a driveline retarder outlet opening (104, 604, 704, 809) and a bypass outlet opening; a valve (106, 606, 706, 806) positioned in the coolant diverter body (101, 601, 701), the valve (106, 606, 706, 806) configured in a first valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) in isolation from the bypass outlet opening, the valve (106, 606, 706, 806) configured in a second valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) and the bypass outlet opening; and a valve controller (402, 805) electrically coupled to the sensor, configured to receive operation data regarding the driveline retarder, the operation data comprising the temperature data and configured to selectively place the valve (106, 606, 706, 806) in the second configuration in response to the operation data indicating that a braking event in which a pedal of the vehicle is depressed for more than a nominal amount of time and the temperature of the driveline retarder being below a predetermined temperature threshold. a coolant diverter body (101, 601, 701) having a coolant inlet opening (102, 602, 702, 808), a driveline retarder outlet opening (104, 604, 704, 809) and a bypass outlet opening; a valve (106, 606, 706, 806) positioned in the coolant diverter body (101, 601, 701), the valve (106, 606, 706, 806) configured in a first valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) in isolation from the bypass outlet opening, the valve (106, 606, 706, 806) configured in a second valve configuration to fluidly couple the coolant inlet opening (102, 602, 702, 808) to the driveline retarder outlet opening (104, 604, 704, 809) and the bypass outlet opening; and a valve controller (402, 805) electrically coupled to the sensor, configured to receive operation data regarding the driveline retarder, the operation data comprising the temperature data and configured to selectively place the valve (106, 606, 706, 806) in the second configuration in response to the operation data indicating that a braking event in which a pedal of the vehicle is depressed for more than a nominal amount of time and the temperature of the driveline retarder being below a predetermined temperature threshold.