1. Find a safe place to pull over ASAP. In the shade if there is an option.
2. Turn the vehicle off, open the hood or bonnet, be very careful if there is steam pouring out, you may want to let it cool down for a bit.
2.5. If everything looks “ok” at a brief visual then we need to check if the cooling fan is working. It should be located between the radiator(front grill area) and engine. Start the car. Is the fan running? If not and the gauge reads hot, there is a fan problem. Try turning the a/c on max. If the fan stays on you can drive the car like this. If the fan is still off, then you need to let the vehicle cool right down. Once it cools you can then drive it, avoid stopping for any period of time with the engine running as the vehicle will need airflow to keep it cool.
3. Let the vehicle cool down. At least an hour.
4. You are going to need to remove the radiator cap. You will want to do this very slowly, preferably with a rag or glove to protect your hand. WARNING, there could be very hot steam and pressurized liquid in there. Open it SLOWLY, stopping to allow steam to escape as you go.
5. You will need to fill up the cooling system if it is low, water will do fine for now. Fill it slowly if the engine is still very hot. If it spits liquid back up at you then you need to let the vehicle cool down longer. Do not worry about filling the overflow reservoir. The cooling system will only draw coolant from there when the system cools completely from operating temperature.
6. If coolant stays in the system and is not pouring out, then there is a good chance you can nurse the vehicle to a service station.
7. Prep the vehicle for driving with a bad cooling system: Open the windows. Turn the interior climate control to hot, panel (blowing at your face) vents and turn the fan on full. A/C must be off. This will allow the interior fan to provide some engine cooling through the interior heat system. It is very important that the A/C system be off as that will contribute a lot of extra heat to the vehicles cooling system, this is why I recommend switching the mode to panel vents. Many vehicles cycle the A/C system in any sort of defrost mode. You can also then direct the panel vents away from you and out the window as much as possible.
8. With the coolant cap still off, start the vehicle. If everything sounds more or less normal then top up the water some more if it goes down after starting. Then place the coolant cap on, but don’t tighten it all the way. If it is a screw on one, then just loosen it a little bit. If it is a tabbed one then just turn it on to the first notch. Basically we want the water to stay in the system while driving but not build up to much pressure and increase the rate of leaking.
9. Drive the vehicle very gently. Monitor the heat coming out of the interior vents and the temperature gauge. If the gauge goes high again you will need to repeat the process or get a tow. If you heat stops coming out of the interior heating system, pull over and shut it off. There is a good chance your coolant has all drained out and the system is near empty.
