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Mysterious Coolant Loss on 2021 Ram 1500 Hemi - No Visible Leaks

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Dan C. · rep 0 · May 22, 3:36 AM · 1 replies · solved · Question

Vehicle: 2021 Ram 1500 Big Horn

Hey everyone,

I've got a 2021 Ram 1500 Big Horn with the 5.7L Hemi, just hit 45,000 miles. For the past few weeks, I've noticed I'm having to top off the coolant reservoir every 1000 miles or so. There's no visible puddle under the truck, no obvious drips, and the engine temperature gauge stays normal.

I do smell a faint sweet odor sometimes, especially after driving, but I can't pinpoint where it's coming from. I've checked the radiator, hoses, and water pump area as best I can, but nothing. Are there any common hidden coolant leaks on these Hemi Rams that I should be looking for?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:36 AM

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ClearTheCode admin answer:

Mysterious coolant loss without visible puddles is a frustrating issue, but it's not uncommon on Hemi engines. The sweet smell is a strong indicator of a coolant leak, even if you can't see it. Here are some common hidden areas for coolant leaks on your 2021 Ram 1500 Hemi:

  1. Water Pump Weep Hole: The water pump can develop a slow leak from its weep hole, which might evaporate before hitting the ground, especially if it's a small leak. Look for crusty residue around the pump housing.
  2. Thermostat Housing: The plastic thermostat housing is prone to cracking or gasket failure, leading to slow leaks that can be hard to spot.
  3. EGR Cooler (if equipped): On some Hemi configurations, the EGR cooler can develop internal leaks, allowing coolant to be burned off in the exhaust, producing the sweet smell without external drips.
  4. Heater Core: An internal leak in the heater core would cause coolant to drip into the passenger footwell or evaporate, leading to a sweet smell inside the cabin. Check for dampness on the passenger floorboard.
  5. Valley Pan Gasket: The valley pan gasket, located under the intake manifold, can fail and allow coolant to leak into the valley of the engine, where it can evaporate or slowly drain without being easily visible.
  6. Head Gasket: While less common at 45,000 miles, a very minor head gasket leak could allow coolant to enter the combustion chamber and burn off. Look for white smoke from the exhaust (especially on startup) or oil contamination (milky oil).

When to see a shop:

  • A professional can perform a cooling system pressure test. This involves pressurizing the system and holding it for an extended period, which often reveals leaks that are otherwise invisible.
  • They can also use a UV dye kit in the coolant. The dye will glow under a UV light, making even tiny leaks visible.
  • If internal leaks (EGR cooler, head gasket) are suspected, further diagnostics like a block test (for exhaust gases in coolant) or borescope inspection may be necessary. Addressing coolant loss promptly is crucial to prevent engine overheating and potential severe damage.
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