If you put too much antifreeze in car engine will it affect the incar heaters?

Yes, putting too much antifreeze (coolant) in a car engine can affect the in-car heater. The heater core is part of the engine's cooling system, and if the coolant level is too high, it can:

* Overpressurize the system: Excess coolant can lead to higher pressure within the cooling system when the engine heats up. This increased pressure can damage components, including the heater core.

* Cause leaks: The pressure from an overfilled system might force coolant past seals or gaskets, leading to leaks in the heater core. This can result in a loss of heating ability or even coolant leaking into the car's interior.

* Airlocks: An overfilled system can make it harder for the coolant to circulate properly, leading to airlocks that prevent adequate heating.

In short, while the heater might work initially, an overfilled system puts it at risk of damage and reduced effectiveness. It's crucial to maintain the correct coolant level as specified in your vehicle's owner's manual.