What happens if you don't bleed air out of coolant system?

If you don't bleed the air out of the coolant system, trapped air can create air pockets that prevent proper coolant circulation. This can lead to overheating, reduced engine efficiency, and potential damage to the engine. Additionally, air pockets can cause erratic temperature readings and hinder the effectiveness of the heating system inside the vehicle. Overall, neglecting to bleed the system can lead to serious mechanical issues over time.