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Coolant Loss on my 2018 Mini Cooper S - What's going on?

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Angela R. · rep 0 · May 22, 7:05 AM · 1 replies · solved · Question

Vehicle: 2018 Mini Cooper S F56

Hey everyone,

I've got a 2018 Mini Cooper S (F56) and I've noticed the coolant level in the expansion tank keeps dropping. I topped it off a couple of weeks ago, and it's low again. I haven't seen any obvious puddles under the car, but I do sometimes smell something sweet, especially after a drive.

The temperature gauge seems normal, and there are no warning lights on the dash yet. I'm worried about potential engine damage if this continues.

Is this a common issue with these Mini models? What are the usual suspects for coolant leaks that aren't always visible? Any advice on what I should check first before taking it to a mechanic? Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 7:05 AM

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ClearTheCode admin answer:

It sounds like you're experiencing a common issue with Mini Cooper models, including your 2018 Mini Cooper S F56, which is a slow coolant leak. Even without visible puddles, a sweet smell is a strong indicator of coolant escaping and evaporating.

Here are the most common culprits for coolant loss in your vehicle:

  1. Water Pump Housing: The plastic housing for the water pump can become brittle over time and develop cracks, leading to leaks. This is often a slow drip that might not reach the ground immediately.
  2. Thermostat Housing: Similar to the water pump, the thermostat housing is also plastic and prone to cracking or gasket failure. Leaks here can be tricky to spot as they might drip onto other engine components.
  3. Coolant Expansion Tank: The tank itself can develop hairline cracks, or the cap might not be sealing properly, allowing coolant to evaporate or seep out under pressure.
  4. Hoses and Clamps: Over time, rubber hoses can degrade, or clamps can loosen, leading to minor leaks. Inspect all visible hoses for signs of wetness or residue.

When to see a shop: Given that you're consistently losing coolant, it's crucial to have this addressed promptly to prevent potential overheating and more severe engine damage. A professional shop will perform a pressure test on the cooling system. This involves pressurizing the system to mimic operating conditions and then visually inspecting for leaks. They can also use a UV dye to pinpoint the exact source of the leak, especially if it's subtle.

While a direct leak might not always trigger an OBD code, if the coolant level drops significantly enough to affect engine temperature readings, you might eventually see codes like:

  • P0117: Engine Coolant Temperature Sensor 1 Circuit Low
  • P0118: Engine Coolant Temperature Sensor 1 Circuit High These indicate issues with the temperature sensor, often a symptom of low coolant or an air pocket in the system.

Don't delay in getting this checked out. A small leak can quickly become a major problem.

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