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Why is My Car Overheating?

By Edited Jun 28, 2014 0 1

It's one of the age-old automotive troubleshooting questions - "why is my car overheating?". Unfortunately, there is no one single answer, which makes these kinds of issues extremely frustrating, especially if you have never worked on vehicles before. The solution to your problem could involve the radiator, thermostat, head gasket, water pump, coolant level, circulation, fan, and even the radiator hoses.

You're here because you need help. You're wondering, "why is my car overheating?" - and I have been in those same shoes before as well. That is one reason I decided to write this article, so you can discover and rule out some of the most common reasons for this.

Below you will see a list of sections divided up into the most prevalent questions related to, "why is my car overheating?". Scroll through and find the heading that is most relevant for your personal situation, and hopefully you will be able to get a better idea of how to fix your automobile problem. Under each section you will see a list of possible causes that are arranged from most plausible to least, generally speaking of course. At the end of this article I will briefly go over each individual cause and how you can troubleshoot/fix it.

Keep in mind that this is all generalized and every vehicle is different in both subtle and obvious ways. It's always nice when you can find answers to questions like "why is my car overheating?" online so conveniently, but sometimes it's just best to have somebody take a look at it to get the most accurate advice. In the meantime, check out the information in this article.

Before reading on, it's important to mention that if your engine is running hot and it reaches the red on your temperature gauge, pull over immediately and turn off your vehicle. Never drive when you're in the red; it's a good way to warp your heads, ruin your engine, and/or blow your radiator. Now, let's get started!

Why is my car overheating even in cold weather?


A lot of people don't realize that this can happen even in the winter months. They figure that since it's cold outside, it will keep the engine cool enough to not have to worry about. However, there are quite a few reasons for why my car is overheating even when the temperatures are below freezing.

Possible Causes
  1. Thermostat stuck closed
  2. Air bubbles in system
  3. Low coolant/leak
  4. Frozen coolant
  5. Faulty water pump
  6. Faulty radiator
  7. Blown head gasket

Why is my car overheating at low speeds?


Low speeds are one of the most common environments to experience this problem. Unfortunately, there are also a lot of possible reasons for it, which leaves a lot of guesswork for you.

Possible Causes
  1. Radiator fan
  2. Low coolant/leak
  3. Air bubbles in system
  4. Thermostat stuck closed
  5. Faulty water pump
  6. Faulty radiator
  7. Pressure/circulation problems
  8. Blown head gasket

Why is my car overheating while I'm idling?


Very similar to the previous question, but if you just skipped straight to this one, I'll tell you this is another common issue with similar possibilities to consider.

Possible Causes
  1. Radiator fan
  2. Low coolant/leak
  3. Air bubbles in system
  4. Thermostat stuck closed
  5. Faulty water pump
  6. Faulty radiator
  7. Pressure/circulation problems
  8. Blown head gasket

Why is my car overheating when the fan still works?


Usually when your engine starts running too hot, one of the easiest and quickest things to check first is the fan; but when you notice that it's still functioning, where do you look next? Sadly, you're just breaking the surface of the list of potential culprits.

Possible Causes
  1. Low coolant/leak
  2. Thermostat stuck closed
  3. Faulty water pump
  4. Faulty radiator
  5. Air bubbles in system
  6. Pressure/circulation problems
  7. Blown head gasket

Why is my car overheating when the coolant level is full?


Other than checking the fan, making sure you have enough antifreeze is a must. Not only should you check the level, but you should also make sure it is the correct mixture of water and antifreeze for the temperatures you're driving in, and also that there are no small leaks. If it's not the antifreeze levels, then it could be any of these:

Possible causes
  1. Radiator fan
  2. Thermostat stuck closed
  3. Air bubbles in system
  4. Faulty water pump
  5. Faulty radiator
  6. Pressure/circulation problems
  7. Blown head gasket

Why is my car overheating with white smoke coming from the exhaust?


If you're asking this question, then I'm sorry to say you have come across the worst-case scenario when it comes to automotive troubles. If you see white smoke coming from the exhaust, and your engine is running hot, there is usually only one horrible culprit…

Possible Causes
  1. Blown head gasket

Why is my car overheating with no coolant leaks present?


If you're not seeing any leaks, and you've never worked on vehicles before, then you may really be scratching your head at this one. Better get someone who knows a thing or two about this subject though, because there's quite a few more reasons why the engine is running hot when there are no leaks present.

Possible Causes
  1. Thermostat stuck closed
  2. Radiator fan
  3. Air bubbles in system
  4. Faulty water pump
  5. Faulty radiator
  6. Pressure/circulation problems
  7. Blown head gasket

Why is my car overheating at high speeds?

High speeds will naturally cause the engine to run hot, but the cooling system is supposed to compensate for that. If you're experiencing high temperatures at high speeds it could be any one of the following:

Possible Causes
  1. Thermostat stuck closed
  2. Faulty radiator
  3. Faulty water pump
  4. Air bubbles in system
  5. Pressure/circulation problems
  6. Radiator fan
  7. Blown head gasket

Why is my car overheating in a short amount of time?


Normally you would have to have your vehicle running for a while in order to experience dangerously high temperatures. However, in some cases you will notice right off the bat that you're going to be having a bad day. We can narrow this down usually to a faulty water pump, but every once in a while it can wind up being something else.

Possible Causes
  1. Faulty water pump
  2. Thermostat stuck closed
  3. Air bubbles in system
  4. Low coolant/leak
  5. Pressure/circulation problems
  6. Faulty radiator
  7. Blown head gasket

Why is my car overheating after driving around for a while?


Driving around town for long periods of time and experiencing high engine temperatures is a pretty common occurrence, and there are many reasons why it could be happening.

Possible Causes
  1. Low coolant/leak
  2. Air bubbles in system
  3. Pressure/circulation problems
  4. Thermostat stuck closed
  5. Faulty radiator
  6. Radiator fan

Why is my car overheating when everything seems to be working properly?


If you've already done some research on the possible reasons why you are having troubles, and you did a check on all the obvious things like the radiator fan, coolant levels, water pump, thermostat, head gasket, and leaks, then there are just a couple of things you may have overlooked, as many people do.

Possible Causes
  1. Air bubbles in system
  2. Pressure/circulation problems

Brief Summary of Possible Causes


Thermostat stuck closed - The thermostat is what allows coolant to flow from the engine to the radiator after it reaches a certain temperature. When it's stuck closed, it prevents all the hot coolant in the engine from circulating and thus causes me to ask, "why is my car overheating?". Check to see if the thermostat is working by removing it and placing it in a pot of boiling water. Watch to see if it opens up after a few minutes. If it doesn't, replace it, and make sure you put the new one in facing the correct direction (spring faces towards engine block in most cases).

Air bubbles in system - This is a commonly overlooked issue that can be easily fixed at home. Park your vehicle on a slight incline--engine up--and take the radiator cap off (make sure the engine is cool). Start the ignition and look inside the radiator or thermostat housing to watch the flow of antifreeze. If you see bubbles in the coolant, let the engine run for about 15 minutes to let all the air bleat itself out.

Low coolant/leak - Check under the radiator cap and also in the plastic coolant reservoir to see if the levels are okay. If not, top them off. Check for leaks after you park the vehicle. You will see it dripping onto the ground if there are any significant leaks, and you may also hear a hissing noise and smell something sweet coming from the engine. This is a sign of a small leak. Avoid using store-bought seals that you pour directly into the radiator as these tend to cause more long term problems and you'll soon be asking "why is my car overheating?" more than you can bear. See a mechanic at your earliest convenience.

Faulty water pump - This is something that most people would need to go to a mechanic for. If you hear a weird ticking or screeching noise coming from your water pump or notice it's leaking, it's time to pull that sucker out and slap a new one in, because it's almost definitely why my car is overheating.

Radiator fan - You can check to see if your radiator fan is working by watching it when your engine is hot, or you can also listen for it; either way it's pretty easy to identify. Replacing it is a different story though. It's definitely feasible to do by yourself but it might be best to see an expert.

Pressure/circulation problems - Take your vehicle to a repair shop or an auto parts store and ask them to do a pressure test on your cooling system. Even something as small as a pinhole leak can throw your pressure all out of whack and cause circulation problems, which could very well be why my car is overheating. It could also be an early warning sign of a blown head gasket.

Faulty radiator - It's pretty hard to figure out whether or not your radiator is broken or not. After all other possibilities have been exhausted, I recommend taking your vehicle to a radiator repair shop and have it looked at.

Blown head gasket - Pull out your dipstick and look at the oil. If it's milky white and bubbly, you've got problems. White smoke coming from the exhaust is another red flag, along with the smell of exhaust inside your coolant reservoir. Stop driving your vehicle and call a mechanic as soon as possible, or the question of "why is my car overheating?" will be the least of your problems.

Frozen coolant - If you don't have the correct mixture of antifreeze and distilled water for the temperatures you're driving in, it is possible for your coolant to freeze and cause your engine to get too hot because of poor or no circulation. Make sure you always have the correct mixture of coolant and you'll be fine.

"Why is my car overheating? I don't know yet because I'm still going down the massive list of possible reasons!" Vehicle troubles can be a pain, and even though this particular issue can be frustrating because of all of the potential culprits lurking around, it's actually relatively easy to identify and even fix in many cases when compared to a lot of other automotive glitches. Good luck to you and stay safe!

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Comments

Jun 30, 2010 2:17pm
Philtrate
Well organised and laid out article. I like the fault finding system, and the positive attitude towards non-mechanical people, Thanks
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