2015 579 MX 13 surge tank issues

You using OEM reservoir or aftermarket? Grime in tank usually causes float to stick. If you trust your driver, a magnet taped to the sensor works too.

 

Every paccar mx13 I’ve driven and a bunch of friends have low coolant codes in cool weather upon startup unless you overfill it .

 

I agree there is a fine line between the cold full line and when the light comes on. Not much give there. I also will fill them chock full and they always have room to expand without pushing out any excess. Near impossible to overfill.

 

Just a thought, try a dab of RTV on new sensor when installed or zip tie. Had 2 where heavier than normal vibration (damper) caused the "placement nubs" to wear more than normal allowing then sensor to drop down over time and give false "low" reading even though the tank was good.

 

I have a 2019 T680 with the same problem. I hacked a solution to the problem with a magnet and 2022 version of baling wire. All alarm lights and sounds are off and truck runs fine. Just do your precheck and eyeball the antifreeze reservoir, keep an eye on your engine temperature gauge and use your nose to sniff out any antifreeze odor. You don't need no stinking low coolant sensor. Pics are attached.

 

I have a 2019 T680 with the same problem. I hacked a solution to the problem with a magnet and 2022 version of baling wire. All alarm lights and sounds are off and truck runs fine. Just do your precheck and eyeball the antifreeze reservoir, keep an eye on your engine temperature gauge and use your nose to sniff out any antifreeze odor. You don't need no stinking low coolant sensor. Pics are attached.