Q: I have nissan Teana 230 JM. Engine is getting hot and some smoke is coming when running 20-30 kms, but not showing any warning...

Of course, first make sure that the engine is fully and correctly configured for CNG. If not, that alone will create problems, including overheating. If the engine is configured for CNG but it is still overheating, you can request an engine overheating diagnostic. The most common causes of overheating include low coolant level (including that due to leaks), a faulty thermostat, a plugged radiator, a faulty radiator pressure cap, collapsed hoses, non functioning cooling fans, and a faulty water pump or drive belt. Certain engine faults, such as a leaking head gasket, poor engine running condition or exhaust blockages can also cause overheating. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request the engine overheating diagnostic that I referred to and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.