Most cars have a temperature gauge on the dash. Some just have a warning light. The normal reading for a gauge is usually just below halfway. If your temperature gauge should read abnormally high, which I call near or in the red zone, there are some important steps to take to keep from damaging your engine and to keep you safe. It is not unusual to hear a little gurgling sound from under the hood, especially on a very hot day with your air conditioner on. However, puddles of green fluid under the engine are not normal.
It does not take long to damage an engine when it overheats. If your gauge never quite reaches the red zone, then generally you need not worry about damage. However, if it is operated in the red zone while driving or idling,even for a few minutes, you can potentially damage or weaken the engine.
First off you should form a habit of glancing at your gauges periodically. I usually look at all of them when I check how much gas I have.
If you are driving down the highway or sitting in traffic, and the gauge is in or near the red zone, the best thing for the engine is to shut it off and let things cool down. Although it seems counterintuitive, immediately turn on the heater, which will help dissipate heat.
Remember, your personal safety is more important than your engine. So, if you are in heavy traffic on the freeway, get to a place where you feel safe first, then shut off the engine. The easiest thing to do is call AAA or other roadside service and let them take it from there.
If you are so inclined, and make it home and want to see for yourself, proceed with caution. I recommend you use gloves and safety glasses just to be safe.
The most common reason for overheating is low coolant, which is a result of a leak from perhaps the water pump, the radiator, or a coolant hose.
Remember, hot coolant is under pressure and turns to steam when shooting out a small hole, so use CAUTION. If you hear a hissing noise or see steam coming from under the hood, WAIT for the engine to cool down (which may take several hours).
Your owner’s manual will describe in detail your specific cooling system and where to find what. The example I am using consists of a common pressurized cooling system with a non-pressuring overflow jug. If you want to check the coolant level, first locate the radiator cap, follow the small hose which will lead to the overflow jug with a hot (high) and cold (low) level.
Coolant expands and contracts naturally, so the coolant moves from the radiator to the overflow jug as it warms up and then travels the other way when cooling down. This is why an overflow jug has a high and low or hot and cold level marks. The overflow jug is normally see-through, but over time it discolors, making it hard to see the level. So, once again, if there is no steam or hissing noise, you can remove overflow jug cap and look inside. If it is empty, then your radiator is likely low.
Next, if you want to add coolant to the radiator, you must remove the radiator cap and add directly. Remember, you MUST wait until the engine is cool, which may take hours, before removing the radiator cap. A little trick I use is to squeeze the upper radiator hose. If it squeezes easily then the closed system is not under pressure anymore. Next, remove the radiator cap by pushing down while turning counterclockwise about a quarter turn or so. You won’t need any tool for this. Normally, the level should be within an inch of the fill neck. If not, you will need to add a 50/50 mixture of antifreeze and water. Most systems hold about two gallons, so keep track of roughly how much you add as this info is helpful to your service technician. Add the same mixture to the overflow, to the cold level. Replace your radiator cap, start your engine and go on a little test drive. It takes about five to ten minutes for an engine to warm up, so at that time the gauge should read normal.
Coolant does not evaporate, so if it was low, it went somewhere. This is the time to make an appointment with your favorite repair shop to ensure you don’t get stranded or damage your engine. It is helpful to tell the shop the details, like what the gauge read and for how long. Your service advisor will also want to know if you were driving down the road or sitting in traffic, if the air conditioner was on or off, and if the engine has ever overheated before, and if so, what was found.