One of the worst problems that can happen to your Toyota 4Runner is overheating. Common symptoms of overheating include smoke coming from under the hood, a pegged temperature gauge, and a blown head gasket.
Overheating can cause a lot of expensive damage to the engine. A blow head gasket or a cracked head/block are much more expensive to repair than a thermostat or water pump.
How Your 4Runner’s Cooling System Works
Your 4Runner’s cooling system works by cycling the engine coolant from the engine through the radiator. The water pump pushes the water through the entire system. The thermostat opens up once the engine reaches operating temperature and allows coolant in.
If any part of this system fails, your 4Runner will eventually overheat.
Toyota 4Runner Overheating Symptoms
Here are the most common symptoms of a vehicle overheating.
1. Gauge/Temp Light
Your 4Runner will be equipped with a temperature warning light and/or a temperature gauge. The most common symptom of overheating is the temperature light coming on.
If this light does come on, make sure that you get off the road quickly and safely. Driving while overheating can cause long term engine damage.
2. White Smoke
If your 4Runner’s engine gets hot enough, the coolant will begin to boil over and manifest itself as steam coming up from under the hood. It does this to relieve the pressure on the cooling system before lasting damage can be done to it.
3. Blown Head Gasket
If your 4Runner is run for too long of a period while overheating, the head gasket may blow. Bad head gasket symptoms include white smoke coming from the tail pipe, rough idle, and oil in the coolant. Shutting down before it overheats, or as soon as you see that it is overheating will usually prevent this from happening.
Overheating Causes: Toyota 4Runner
The first thing that you need to do is check your 4Runner’s overflow container. If it is full, you can rule out low coolant or a coolant leak, and skip the next section.
Low coolant is the most common reason that your 4Runner will overheat. Low coolant is a symptom of a cooling system leak of some kind. It doesn’t just randomly disappear. Here are some of the reasons that your coolant may run low:
- Radiator damage
- Cracked/bad radiator hose
- Bad radiator cap
- Thermostat housing damage
- Water pump gasket
There are a lot of places to look for a radiator leak. Make sure that you don’t take the radiator cap off when the engine is warm. In fact, you really should not need to take it off at all, unless the coolant is leaking from the cap itself.
A slow leak can be more difficult to find than a quick leak, since the coolant can evaporate before it has a chance to show itself.
If you are loosing fluid, but can’t readily see the leak, UV dye is a great tool to locate it. It really does work well. If you aren’t finding anything even with the dye, take a look at the rear exhaust. Do you have a lot of white smoke? That’s a very good indication that you have a blown head gasket.
Bad Radiator Fan
While going down the road the movement of air through your 4Runner’s radiator will usually be enough to keep it cool, without the help of the fan. It’s when you are hardly moving that the radiator fan is going to do the work of keeping air flowing into the radiator.
If you have a temperature gauge, you’ll notice that the temp will usually cool down when you get onto the highway and get moving into clean air. When the cooling system itself is bad, usually the opposite will happen.
One of the most common reasons that a vehicle overheats is a bad thermostat. If your radiator overflow is full (and you radiator fan is kicking on), it is very likely that a bad thermostat or bad water pump are causing your 4Runner to overheat. Of these two, the thermostat fails more often than the water pump. It’s also much more affordable and easier to get to.
Bad Water Pump
The water pump is driven by the serpentine belt attached to the 4Runner’s engine. Has your belt been squeaking when you start up, or when you are on the road? That can be an indication of a bad serpentine belt.
When your water pump does go bad, it will often leak water. Or it’ll make a grating noise. This is due to the bearings inside of it going bad. Here’s a great video on how to tell if your water pump is bad.
A good trick to tell if the water pump may be bad is to put it into neutral and rev the engine up a few thousand RPM for a few seconds. If the temperature went down, that can indicate a bad water pump. Why? A dying pump may get spinning enough to move the coolant with the increase in RPM.
Conclusion: 4Runner Overheating Symptoms & Causes
There can be a lot of different reasons that your Toyota 4Runner’s engine would overheat. We hope this helps you find out why. If there is anything that you would like to add, please leave a comment below. Good luck!