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2018 Charger R/T Overheating & Low Coolant - DIY Coolant Flush?

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Mike T. · rep 0 · May 24, 3:20 PM · 1 replies · solved · Question

Vehicle: 2018 Dodge Charger R/T

Hey everyone,

I've got a 2018 Dodge Charger R/T with the 5.7L Hemi, and lately, I've noticed it running a bit hot, especially in stop-and-go traffic. The temperature gauge creeps up higher than usual, and I've had the 'Check Engine' light come on a couple of times. When I checked the coolant reservoir, it was pretty low.

I scanned for codes, and I'm getting a P0128, which points to a 'Coolant Thermostat (Coolant Temperature Below Regulating Temperature)' issue. I'm wondering if it's just a stuck thermostat or if I might have a leak somewhere.

I'm fairly handy and was thinking about tackling a coolant flush and thermostat replacement myself. Is this a feasible DIY for my Charger, and what specific type of coolant should I use? Any tips on bleeding the system afterward would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 3:20 PM

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ClearTheCode admin answer:

It sounds like you're on the right track with diagnosing the P0128 code and considering a thermostat replacement and coolant flush for your 2018 Dodge Charger R/T. This is a common issue and can often be a DIY project if you're comfortable with basic automotive tasks.

Here's a breakdown of what you should do:

  1. Inspect for Leaks First: Before flushing, carefully inspect all hoses, the radiator, water pump, and heater core connections for any signs of leaks (pinkish residue from the coolant). A low coolant level could indicate a leak rather than just evaporation.
  2. Thermostat Replacement: The P0128 code strongly suggests a faulty thermostat that's stuck open, preventing the engine from reaching optimal operating temperature, or a sensor issue. Replacing it is a good first step. Ensure you get an OEM or high-quality aftermarket thermostat designed for your 5.7L Hemi.
  3. Coolant Type: For your 2018 Dodge Charger, you must use OAT (Organic Acid Technology) coolant, specifically Mopar Antifreeze/Coolant 10 Year/150,000 Mile Formula or an equivalent that meets Chrysler MS-90032 specification. It's typically purple or pink in color. Do not mix different coolant types, as this can lead to gelling and severe engine damage.
  4. Coolant Flush Procedure:
    • Ensure the engine is cool. Drain the old coolant from the radiator drain plug and the engine block drain plugs (if accessible and recommended for a complete flush).
    • Refill with distilled water, run the engine with the heater on until it reaches operating temperature, then drain again. Repeat until the water runs clear. This flushes out old coolant and contaminants.
    • Install the new thermostat.
    • Refill with the correct 50/50 mix of OAT coolant and distilled water.
  5. Bleeding the System: This is crucial for preventing air pockets, which can cause overheating.
    • With the radiator cap off, start the engine and let it run with the heater on high.
    • Squeeze the upper and lower radiator hoses repeatedly to help dislodge air bubbles.
    • Keep an eye on the coolant level in the radiator and top it off as needed.
    • Some vehicles have a bleeder screw; if yours does, open it until a steady stream of coolant comes out.
    • Once the thermostat opens and the system stabilizes (no more bubbles), replace the radiator cap. Drive the car and recheck the coolant level in the reservoir after a few cool-down cycles.

When to See a Shop:

  • If, after replacing the thermostat and flushing the system, the overheating persists or the P0128 code returns.
  • If you find significant leaks from the radiator, water pump, or heater core, as these repairs can be more involved.
  • If you're uncomfortable with any part of the process, especially draining and refilling, as improper bleeding can lead to severe engine damage.
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