“Why am I topping up coolant every few weeks — is thermostat failure the sneaky leak culprit?”

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“Why am I topping up coolant every few weeks — is thermostat failure the sneaky leak culprit?”

Some users say they need to refill coolant more often than expected — even without visible leak spots o r puddles under the car. Could a failing thermostat housing o r valve or its seal/gasket leak internally o r vent coolant under pressure, causing slow coolant loss? o r is frequent coolant top-up in Tiggo 8 Pro mostly due to radiator cap/hoses/radiator issues rather than thermostat itself?

Talha Kyanii asked on 06 Dec 2025 09:26:42 am

1 Answer

6 views |

Gari Master - on 06 Dec 2025 09:27:37 am

A failing thermostat rarely causes coolant loss directly — but it can indirectly cause it.

How thermostat issues cause coolant loss:

If thermostat stays closed → engine overheats → coolant expands too much → overflow tank pushes out coolant

Pressure spikes can push coolant past:

weak radiator cap

aging hoses

small hairline cracks in thermostat housing

Coolant may evaporate as steam instead of dripping

More common reasons for coolant top-up in Pakistan:

Loose hose clamps

Radiator cap not sealing properly

Slow leak from water pump seals

Poor-quality coolant evaporating faster

Micro-cracks in plastic components due to heat

What to check:

Radiator cap pressure rating

Thermostat housing / gasket

Hoses for tiny leaks

Radiator for seepage

Water pump for moisture traces

If the coolant disappears without visible leaks, overheating from a stuck thermostat is a major possible cause.