[How to Fix] Car Engine Temp Spikes Then Return Normal

Car Engine Temp Spikes Then Returns Normal

If you’ve been driving for a while, you might have encountered a situation where your car’s engine temperature gauge shoots up, only to return to normal soon after. While you might be tempted to brush this off, I’m here to tell you—it’s a symptom you shouldn’t ignore. 

In my experience as a mechanic, I have learned that maintaining the proper engine temperature is crucial for your vehicle’s long-term performance and safety.

When your engine operates outside the ideal temperature range, you’re not just risking a breakdown; you could also be causing long-term damage that might cost you more than you some money.

In today’s post, I’ll walk you through the causes behind these sudden spikes in engine temperature and how to diagnose and fix the issue to get things running smoothly again.

Causes of Engine Temperature Spikes

Engine temperature spikes can be disturbing, especially if you don’t know what’s causing them. While some factors can be less harmful, others might signify deeper issues that require immediate attention.

Understanding these underlying causes is the first step to diagnosing and resolving the issue effectively. The following are some of the most common causes;

1. Overheating

Overheating is often the most common reason for temperature spikes, it can occur when your engine works too hard i.e., strenuous driving conditions like steep climbs, heavy loads, or simply running your vehicle for an extended period in hot weather.

Car overheating

2. Faulty Thermostat

The thermostat regulates the coolant flow between your engine and the radiator. When it’s malfunctioning, it can either stick open or closed, causing temperature irregularities. A stuck-closed thermostat will prevent coolant from reaching the engine, causing it to overheat.

3. Radiator Issues

A clogged or damaged radiator will be unable to dissolve heat effectively, leading to increased engine temperature. Additionally, if the radiator fans aren’t working as they should, they won’t be able to cool the coolant, and this leads to more problem.

4. Coolant Problems

Low coolant levels or using the wrong type of coolant can cause temperature spikes. The coolant absorbs heat from the engine and dissipates it through the radiator. If there’s not enough coolant or if it’s the wrong kind, it won’t perform this function effectively.

5. Other Mechanical Faults

Various other issues can lead to temperature fluctuations. These can include problems with the water pump, belts, or even leaks in the cooling system. In some instances, a blown head gasket can also cause spikes, although other, more severe symptoms usually accompany this.

Symptoms to Watch For

When it comes to engine temperature spikes, sometimes the signs are subtle, while other times they’re pretty hard to miss. Either way, it’s important to know what to look out for so you can solve the issue before it escalates into something more severe. Here are some common symptoms to note:

1. Temperature Gauge Rising

One of the most noticeable signs of engine temperature spikes is that the temperature gauge on your dashboard suddenly shoots up. While fluctuations are normal during specific driving conditions, a rapid spike is usually a red flag and a call to check the engine.

2. Warning Lights

Modern vehicles are usually designed with warning lights that alert you to various issues, including overheating. If you see a warning light alongside a rising temperature gauge, it’s a clear sign that you need to check the car’s engine.

3. Unusual Smells

Overheating can produce an unmistakable smell, often described as a “sweet” or “syrupy” odor. This is the smell of coolant burning off, and it’s an indicator that something is wrong.

4. Reduced Engine Performance

You might notice your vehicle struggling with tasks that are typically a breeze, like accelerating or climbing hills. Reduced engine performance can be a byproduct of the engine trying to protect itself from overheating.

Tools and Supplies Needed To Fix The Engine

Before you begin fixing your vehicle, gathering the right tools and supplies is important. Trust me, the last thing you want is to be halfway through a repair only to realize you’re missing something important. Below are what you’ll need to get your car up again.

Basic Tools

  1. Screwdrivers (both flat-head and Phillips)
  2. Adjustable wrench
  3. Pliers
  4. Funnel.

Specialized Tools

  1. Radiator pressure tester
  2. Thermostat tester
  3. Voltmeter (for checking electric fans).


  1. Coolant (The type recommended by your vehicle manufacturer)
  2. Distilled water (for diluting coolant if necessary)
  3. Rags or paper towels
  4. Rubber gloves
  5. Safety goggles
  6. Buckets (for draining old coolant).

Step-by-Step Diagnosis

Once you’ve gathered all your tools and supplies, you’re ready to begin diagnosing the issue. While the causes of engine temperature spikes can vary, a step by step diagnosis can help you identify the root problem more efficiently. Here’s how to go about it:

Coolant levels

1. Check the Coolant Levels

  1. Wait for the Engine to Cool: Wait at least 30 minutes after turning off the car before opening the engine. Never open the radiator cap while the engine is hot, this can be dangerous for you.
  2. Open the Radiator Cap: With the use of a rag, carefully open the radiator cap.
  3. Check the Level: The coolant should be up to the “full” line. If it’s below, you may need to add more coolant. Low coolant level can be a sign of a leak, you should keep an eye out for puddles under the car.

2. Inspect the Thermostat

  1. Locate the Thermostat: To find the thermostat, check your car’s manual.
  2. Test Functionality: You can either use a thermostat tester or place the thermostat in boiling water to see if it opens and closes as it should.

3. Check the Radiator and Fans

  1. Visual Inspection: Look for visible signs of damage or clogging on the radiator fans.
  2. Test the Fans: With the car running, observe whether the radiator fans kick in when the temperature rises. If you have electric fans, you can use a voltmeter to check if they’re getting power.
Checking radiator

Other Checks

  1. Belts and Pulleys: Make sure all belts are in good condition and properly tensioned.
  2. Water Pump: Check for leaks and listen for unusual noises that might indicate a faulty water pump.
  3. Leak Test: Perform a pressure test on the cooling system to identify any leaks.

How to Fix the Problem

Now that you’ve identified the root cause of your engine’s temperature spikes, it’s time to fix it. Below are solutions to the problems you may have discovered during your diagnosis.

1. Replacing or Refilling Coolant

  1. Drain Old Coolant: Place a bucket under the radiator drain plug and carefully open it to drain out the old coolant.
  2. Refill: With the use of a funnel, refill the radiator with a mixture of coolant and distilled water, following your manufacturer’s guidelines.
  3. Run Engine: Turn on the engine and let it run for a few minutes with the radiator cap off to let air bubbles escape.
  4. Check for Leaks: Make sure there are no leaks from the radiator or hoses.

 2. Thermostat Replacement

  1. Locate the Thermostat Housing: The thermostat housing can usually be found near the engine block, connected by a radiator hose. However, you can also consult your car manual.
  2. Remove Old Thermostat: Unscrew the bolts holding the housing and remove the old thermostat.
  3. Install New Thermostat: Place the new thermostat into the housing, ensuring it fits snugly.
  4. Reassemble: Screw the housing back into place and reconnect any hoses or wires.

3. Radiator and Fan Repairs

  1. Clean or Replace Radiator: If your radiator is clogged, it may just need a good cleaning. In more severe cases, a replacement may be necessary.
  2. Fan Replacement: If the fans are not operating correctly, and you’ve confirmed it’s not an electrical issue, replace them.

Other Repairs

  1. Water Pump: If your water pump is the issue, it is typically a professional job due to its complexity.
  2. Belts and Pulleys: Replace any worn belts and adjust tension as needed.
  3. Sealing Leaks: If you identified any leaks during your pressure test, use a sealant or replace the leaking component as required.

Preventative Measures to Avoid Future Spikes

Even after you’ve addressed the immediate issue, taking some preventative steps can go a long way in Ensuring that there are no future occurrences of temperature spikes. This is also an excellent way to extend the lifespan of your vehicle. Check the following;

  • Regular Coolant Checks: Check your coolant levels during your regular oil changes or at least every 3-6 months. Low levels can be a precursor to temperature issues.
  • Annual Radiator Flush: An annual radiator flush can remove any debris and build-up, helping your radiator function more efficiently.
  • Thermostat Checks: While thermostats are generally quite durable, it doesn’t hurt to test them periodically. A faulty thermostat can cause a domino effect on your engine’s temperature control system.
  • Regular Inspections: Make it a point to inspect the belts, hoses, and water pump at least once a year. These components wear down over time and are easier (and cheaper) to replace before they fail completely.
  • Stay Vigilant: Keep an eye on your temperature gauge, especially during extreme weather conditions or while driving in strenuous situations. Catching a problem early can save you from bigger headaches later on.
  • Professional Maintenance: At least once a year, have a professional mechanic perform a full check on your cooling system. They can spot issues you might have missed and can provide expert advice tailored to your vehicle’s make and model.

Final Thoughts

Having the right information about your vehicles will save you some trouble and money. We hope that you found this comprehensive guide on how to fix and prevent engine temperature spikes useful.

With this information, you’re well on your way to ensuring your vehicle operates smoothly and efficiently for years. Remember, regular maintenance is key, if you tried some of the tips above and there seem to be some more problems, do not hesitate to consult a professional.

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