ISX-15 pushing coolant out of reservoir tank -help-

[Waterloo]

I am thinking air compressor. I just put one on my truck, sounds about what mine was doing. Good for a day or two and than back, coolant fluctuated up and down in the clear jug on my ProStar. Then would blow through the cap, remove the cap coolant would drop. That is where I would start. I picked up a reman Cummins compressor from Haldex. The compressor says reman'd in the USA on the box. Was $850 + 600 core. Yes, $600 core. I found this at FleetPride, cheapest I could find in the Detroit area. A new one from Cummins was $1900, reman from dealer was $1,200 w/$300 core.