EWB555 Posted October 9, 2022 Share Posted October 9, 2022 Had a coolant line blow today on a 2016 granite, dumped several gallons out. Was able to get the hose, refill with about 8 gallons of coolant, its full to the max line however low coolant/stop engine light won't go off. Drove the thing loaded with 70K about 8 miles back to the shop after replacing and filling coolant, never got past 195 degrees. Unfortunately, its clearly in power derate, wouldn't go over 45. Any thoughts on what I should check? Quote Link to comment https://www.bigmacktrucks.com/topic/70538-2016-granite-false-low-coolant-alarmderate/ Share on other sites More sharing options...
Dirtymilkman Posted October 10, 2022 Share Posted October 10, 2022 The crappy sensor in the coolant tank. Not the sensor itself but the float in the tank that the sensor reads. Try tapping on the tank where the sensor goes in. It may jar the float loose. Otherwise you need a new tank. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70538-2016-granite-false-low-coolant-alarmderate/#findComment-511433 Share on other sites More sharing options...
Mackpro Posted October 12, 2022 Share Posted October 12, 2022 (edited) We finally cut up one of the expansion tanks that the low coolant sensor pushes into . The sensor pushes up into a pocket with coolant around it but the pocket is sealed and no coolant actually touches the sensor. There is a floating plastic ring with a metal washer inside it that floats up and down over the pocket that holds the sensor. To test we pulled the sensor out of the expansion tank but still plugged in to the harness. With key on , the low coolant alarm went off. We slid a metal washer over the top of the sensor and the low coolant alarm went off as long as the washer was near the top of the sensor. Slide the washer to the bottom and the alarm cones on. Edited October 12, 2022 by Mackpro Quote Link to comment https://www.bigmacktrucks.com/topic/70538-2016-granite-false-low-coolant-alarmderate/#findComment-511634 Share on other sites More sharing options...
Solution EWB555 Posted October 26, 2022 Author Solution Share Posted October 26, 2022 Thanks guys, had a bottle with new sensor at the shop luckily. Changed it the next day no more issue. Funny how things work sometimes, no issues until it legitimately ran low on coolant. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70538-2016-granite-false-low-coolant-alarmderate/#findComment-513532 Share on other sites More sharing options...
Mackpro Posted October 26, 2022 Share Posted October 26, 2022 When the coolant got low the floating ring slid to the bottom of the expansion tank where it got stuck . After refilling with coolant the floating ring was still stuck to the bottom of the tank and now sets off the low coolant alarm. My theory at least. With low coolant codes I’ve had mostly wiring issues ( CHU mostly due to the way the wires are run) and faulty sensors coming in second. Only a few sticking floating rings . Another weird issue ive seen more than once. Driver puts DEF in the fuel tank, DEF eats up injector cup o-rings and now you got fuel in coolant/coolant in fuel. With a little DEF mixed in with the fuel and coolant it physically swells up the expansion tank and makes it look over pressurized. Quote Link to comment https://www.bigmacktrucks.com/topic/70538-2016-granite-false-low-coolant-alarmderate/#findComment-513562 Share on other sites More sharing options...
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