Can using tap water instead of coolant cause radiator damage o r leaks in Hyundai Elantra?
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Can using tap water instead of coolant cause radiator damage o r leaks in Hyundai Elantra?
I’ve been topping up my 2016 Elantras radiator with regular tap water due to availability. Now the radiator has rust around the cap and some leaks. Could the use of hard water have caused internal corrosion and pinhole leaks in the radiator?
1 Answer
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Gari Specialist asked on 10 Jul 2025 16:58:56 pm


es, using regular tap water, especially in cities like Multan, Faisalabad, o r Karachi where water has high mineral content, can cause:
Rust and scale buildup inside the radiator
Pinhole leaks from corrosion
Blockage in radiator fins and cooling channels
Degraded performance of the water pump and thermostat
Tap water contains calcium and magnesium, which stick to metal surfaces inside the radiator. Over time, this reduces heat transfer and increases internal pressure, leading to cracks o r leaks.
What to do:
Always use pre-mixed coolant o r mix only with distilled water
If hard water was used repeatedly, do a coolant flush and inspect the radiator internally
Consider replacing the radiator if corrosion is visible from the filler neck o r cap
Rust and scale buildup inside the radiator
Pinhole leaks from corrosion
Blockage in radiator fins and cooling channels
Degraded performance of the water pump and thermostat
Tap water contains calcium and magnesium, which stick to metal surfaces inside the radiator. Over time, this reduces heat transfer and increases internal pressure, leading to cracks o r leaks.
What to do:
Always use pre-mixed coolant o r mix only with distilled water
If hard water was used repeatedly, do a coolant flush and inspect the radiator internally
Consider replacing the radiator if corrosion is visible from the filler neck o r cap