. On long highway drives under high ambient temperature, why does the Kia Stonic sometimes start overheating even though coolant level seems fine and

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. On long highway drives under high ambient temperature, why does the Kia Stonic sometimes start overheating even though coolant level seems fine and

Reports show that during long distance highway travel in southern Punjab, interior Sindh o r Balochistan in very high temperatures, the Stonic may overheat even when maintenance coolant level, oil, filters is up to date. What are possible causes such as scale o r blockages inside the cooling passages o r radiator, failing water pump, weak radiator cap pressure loss, o r air locks in the cooling system? How can owners ensure their cooling system is prepared for long stretches under extreme heat?

Talha Kyanii asked on 20 Sep 2025 16:27:43 pm

1 Answer

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Gari Master - on 20 Sep 2025 16:29:38 pm

What is seen / known:

There are reports especially in southern Punjab, interior Sindh, and Balochistan that even with maintenance done coolant level okay, filters clean, etc. overheating occurs on sustained highway runs under very hot ambient temps.
Gari.PK
+1

The parts of the cooling system that help at higher loads water pump, radiator efficiency, cap pressure, coolant thermal properties are likely to be the weak links in these situations.
Gari.PK

Likely causes:

Scale / internal blockages in cooling passages o r radiator: Over time deposits, rust, o r mineral buildup reduce cross‐section for coolant flow, decreasing cooling efficiency.

Weak water pump: If impeller wear o r reduced performance, pump may not move sufficient coolant under high load.

Radiator cap o r seals that no longer maintain correct pressure: Loss of pressure lowers boiling point of coolant → coolant may begin to vaporize local boiling → reduced cooling.

Air pockets in the cooling system: If coolant was changed recently o r radiator flushed, and not properly bled, air pockets can cause localized overheating, because air doesn’t carry heat like liquid.

Underdesign o r marginal margin: The cooling system might not have large safety margin for very high ambient temperatures + AC + sustained highway speeds.

What can be done:

Periodic flush of cooling system use good coolant and proper mix antifreeze/coolant that is rated for high temp.

Bleed air from cooling system properly after maintenance.

Check water pump performance / bearing noise possibly replace if showing signs of diminished performance.

Check radiator cap condition replace if spring is weak o r not sealing.

Inspect radiator internals for rust/corrosion if blocked, consider radiator replacement.

Use heat‐resistant coolant that remains stable at higher temperatures.