How do I know if the thermostat valve in my Suzuki Bolan is stuck closed?

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How do I know if the thermostat valve in my Suzuki Bolan is stuck closed?

My Bolan starts to overheat very quickly after just a few minutes of driving. Coolant seems to be present but doesn’t circulate. I’m suspecting the thermostat valve is stuck closed. What are the signs of this, and how can I test it without removing the whole system?

Gari Specialist asked on 10 Apr 2025 12:02:09 pm

1 Answer

22 views |

Gari Master - on 10 Apr 2025 12:17:07 pm

A thermostat stuck in the closed position blocks coolant from flowing into the radiator. This traps heat inside the engine and leads to rapid overheating.

Symptoms of a stuck-closed thermostat:

Temperature gauge rises quickly after just a few kilometers.

Coolant in the radiator doesnt move even after warm-up.

Lower radiator hose remains cold, while the upper one gets very hot.

Overflow bottle may boil o r release steam.

Test method DIY check:

Start the engine cold and let it idle.

Feel both radiator hoses after a few minutes.

If the top gets hot but the bottom stays cold = thermostat may be stuck.

For full confirmation, remove the thermostat and place it in hot water.

If it doesn’t open around 82°C 180°F, it’s faulty.