Q: I added green antifreeze to my car when it had red in it before. Would mixing the two cause a problem with the intake gasket?

It is not advisable to mix coolant types. Over time, a chemical reaction happens between them. This can cause corrosion issues, and the mixture can begin to gel, clogging small coolant passages in components such as the radiator, intake manifold, or heater core. If these components become clogged, the coolant will not circulate properly and can cause overheating issues. If your vehicle is older with high mileage, odds are the intake manifold gasket was in poor condition already.

Mixing coolants would not have caused an immediate failure of the gasket but could contribute to it over a long period of time. If it was running hot and low on coolant, odds are the gasket may have already been leaking and got worse over time.

I recommend having a certified technician, such as one from YourMechanic, come to your location to replace the intake manifold gasket and flush the cooling system, refilling it with the correct coolant as soon as possible.