No power /leaking trans cooler

[rocket051]

2018 Red 33aa noticed coolant leaking ( very little ) while coach was parked. left yesterday to take coach 1 1/2 away for service, before our winter trip. i was surprised as soon as i pushed the throttle down to climb the first minor grade no power, hills on the interstate our speed was 25mph even on level with peddle to the floor hardly any speed increase. NO ERROR CODES. Freightliner service found trans cooler leaking ( replacement on order ) minimal coolant loss so i guess they saw no need to top it off. The only idea from Freightliner on the power loss was MAYBE when coach was on a hill it was sensing low coolant and dropped power. NO CODES? Had to drive it home, same result last hill up to our house low coolant come up. OH I should mention the temp gauge only moved up a little going up long hills. ANY BODY EXPERIENCE THIS?? concerned about driving it back down there

[Ray,IN]

Could the exhaust brake be stuck in the on position? If not properly lubed and/or used frequently they can rust/stick in position.

[rocket051]

Thanks for the idea. I did turn it on and off during the trip. I'll have them check that.