One of the worst problems that can happen to your Mercury Mariner is overheating. Common symptoms of overheating include smoke coming from under the hood, a pegged temperature gauge, and (eventually) a blown head gasket.
If your Mariner is overheating, stop driving it immediately to avoid damaging the engine.
Ignoring an overheating engine can lead to serious engine problems. A blown head gasket, engine block, or cracked head are much more expensive than a thermostat or water pump.
If your Mercury Mariner is overheating, the first thing you should do is check the coolant level.
How Your Mariner’s Cooling System Works
Your Mariner’s cooling cycles engine coolant from the engine through the radiator.
- Water Pump– Your Mariner’s water pump pushes the coolant through the entire system. The coolant starts in the radiator, enters the engine, pulls heat out of the block and heads, and returns to the radiator to be cooled again.
- Thermostat– The thermostat opens up once the engine reaches operating temperature and allows coolant in.
- Radiator– Pulls heat from the coolant before it cycles back into your Mariner’s engine.
- Radiator Fan– Your Mariner’s radiator fan pushes extra air onto the radiator when the engine coolant gets too hot. It is needed when driving at lower speeds.
- Radiator Hoses– Connect the radiator to the water pump and engine block.
If any part of this system fails, your Mariner will eventually overheat.
Mercury Mariner Overheating Symptoms
Here are the most common symptoms that your Mercury Mariner is overheating.
1. Gauge/Temp Light
Your Mariner 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 Mariner’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 occur.
3. Blown Head Gasket
If your Mariner 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 tailpipe, rough idle, and oil in the coolant. Shutting down before it overheats or as soon as you see it is overheating will usually prevent significant engine damage.
Overheating Causes: Mercury Mariner
The first thing that you need to do is check your Mariner’s overflow container. If it is full, you can rule out low coolant or a coolant leak, and skip the next section.
Low Coolant
Low coolant is the most common reason that your Mariner 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
Your Mariner’s radiator could be leaking from the front or back. It can also leak from the cap. If that’s the case, you can fill it and replace the cap.
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 losing 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, 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 Mariner’s radiator will usually be enough to cool the engine 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 your engine is overheating in traffic, and the coolant is full, it’s likely a bad radiator fan or a faulty water pump causing your Mariner to run hot.
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.
Bad Thermostat
One of the most common reasons that a vehicle overheats is a bad thermostat. If your radiator overflow is full (and your radiator fan is kicking on), it is very likely that a bad thermostat or bad water pump is causing your Mariner 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 Mariner’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 could indicate a bad water pump. Why? A dying pump may get spinning enough to move the coolant with the increase in RPM.
Conclusion: Mariner Overheating Symptoms & Causes
There can be a lot of different reasons that your Mercury Mariner’s engine would overheat. We hope this helps you find out why.