It could have burped an air pocket. They should have bled any air out of the system when installing the engine.
Did you get a warranty with the engine replacement? If yes, use it and insist on a repair.
Coolant warning light remains after engine is replaced? hmmm …that’s a tough one. here’s some ideas anyway
- radiator or hose may be leaking. upon visual inspection (engine cold) is the coolant in the radiator actually low ? if it is low, then something is leaking somewhere. It could be any part of the cooling system including sensors that plug into the cooling jacket, hoses, heater core, radiator, radiator cap etc.
If coolant isn’t actually low
coolant level sensor is faulty
problem in connection between sensor and ecm
ecm malfunction (presuming they re-installed the original ecm)
air bubble in cooling system
Why was the engine replaced btw? Did they do a long block or short block replacement?
It sounds like the air in the cooling system worked its way to the reservoir after being driven and then the cooling system was topped off, there may not be a problem. If the cooling system becomes low again there may be a leak in the cooling system.