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2018 Dodge Challenger R/T Overheating - Coolant Flush or Thermostat?

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Melissa G. · rep 0 · May 22, 5:47 AM · 1 replies · solved · Question

Vehicle: 2018 Dodge Challenger R/T

Hey everyone,

I've got a 2018 Dodge Challenger R/T with about 75,000 miles on it, and lately, I've noticed it's running a bit hot, especially in stop-and-go traffic or on longer drives. The temperature gauge creeps up past the halfway mark, sometimes getting close to the red, but it hasn't fully overheated yet. I've checked the coolant reservoir, and the level seems okay, though it's been a while since I've done a full flush.

Could this be a sign that I need a coolant flush? Or is it more likely a failing thermostat? I'm comfortable doing some DIY work, but I want to make sure I'm tackling the right problem. What type of coolant should I be using if I do a flush? Any specific steps or things to watch out for on the 5.7L HEMI?

Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:47 AM

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ClearTheCode admin answer:

It sounds like you're experiencing early signs of an overheating issue, which is wise to address promptly. Given your mileage, a coolant system refresh is definitely a good place to start, but it's important to consider other potential culprits as well.

  1. Diagnose Further: Before jumping to a full flush, observe if the issue is consistent. Does the heater blow hot air when the engine is warm? If not, it could indicate low coolant or a clogged heater core. If you have access to an OBD-II scanner, check for any pending or stored codes, though overheating often doesn't trigger a specific code until it's severe.

  2. Coolant Flush Procedure:

    • Coolant Type: For your 2018 Dodge Challenger R/T with the 5.7L HEMI, you must use Mopar OAT (Organic Acid Technology) coolant, typically dyed purple or pink. Mixing coolant types can lead to gelling and severe engine damage. Always use a 50/50 mix with distilled water.
    • Steps:
      1. Ensure the engine is completely cool.
      2. Place a large drain pan under the radiator draincock (petcock).
      3. Open the draincock and remove the radiator cap to allow the coolant to drain.
      4. Once drained, close the draincock. You can optionally flush with distilled water until it runs clear, but ensure all water is drained afterward.
      5. Refill with the correct 50/50 OAT coolant mix through the radiator fill neck.
      6. Start the engine with the radiator cap off and heater on full blast. Allow it to warm up, squeezing the upper and lower radiator hoses to help burp air out. Top off coolant as needed.
      7. Once the thermostat opens and coolant circulates, install the radiator cap. Check the reservoir level and top off if necessary.

  3. Thermostat Check: A failing thermostat is a common cause of overheating. If it's stuck closed, coolant won't circulate properly. You can test it by observing the upper radiator hose: it should get hot once the engine reaches operating temperature. If the engine is hot but the hose is cool, the thermostat might be faulty. Replacing it is a relatively straightforward DIY task.

  4. Other Potential Causes:

    • Radiator Fan: Ensure your cooling fans are engaging when the engine gets hot, especially in traffic.
    • Water Pump: A failing water pump can lead to poor coolant circulation. Look for leaks around the pump or listen for unusual noises.
    • Clogged Radiator: External debris or internal blockages can reduce cooling efficiency.

When to See a Shop: If a coolant flush and thermostat replacement don't resolve the issue, or if you notice significant coolant leaks, steam from the engine bay, or persistent high temperatures, it's crucial to take your Challenger to a qualified mechanic. Ignoring persistent overheating can lead to serious engine damage, including head gasket failure or a cracked block.

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