Car Specs: Suzuki Alto VXR 2005 Model + Manual + Petrol

Usually, my car's temperature gauge gives a perfect idea of the engine, in normal weather usually it behaves normally when I'm driving in the city and temperature reaches a little bit higher the fan is automatically switched on. it kept on until its coolant the temperature.

In winter when I'm driving on highways at the speed of 110-120 km/H. the temperature gauge reduces to zero or below and the car starts jerking. when I stop for a moment or two, the temperature gauge goes higher and higher and within no time temperature goes to normal and I can drive again without facing any jerks.

Around 10 minutes after this again temperature drops to zero and I have to face the same problem.

A few mechanics inspected my car and couldn't find any issue in it.

  • 1
    A malfunctioning/wrong thermostat comes to mind - if it opens too soon, then the water (engine) never really heats up. In the old days at least, replacing it was a "cheap fix". Was its operation tested by the shop? – mike65535 Nov 29 '18 at 13:34

It may be that your thermostat isn't closing or isn't closing fully. The thermostat is designed to include the radiator in the path that circulating coolant follows only when it reaches a specified temperature. This will typically be around 88 degrees Celsius and most vehicles are designed to operate at an optimum temperature (typically around 90 degrees Celsius).

If your thermostat doesn't close properly, the radiator will cause the coolant temperature to drop below the optimum running temperature which can cause poor running.

Another reason for this behaviour may be that there is an air lock / air bubble trapped somewhere within the system. When filling or topping up the coolant it is important the seat the HVAC controls for full heat in the cabin to prevent air getting trapped in the heater matrix. It's also important to "burp" the system which is usually done by running the engine briefly with the coolant cap removed and squeezing the bottom hose (different vehicles have a different procedure, some have bleed screws).

Finally, it may be that you simply don't have a strong enough concentration of anti-freeze in the system and the coolant is partially icing up in the system.

Out of all scenarios, I'd think that the thermostat the most likely. Draining the system, replacing the thermostat and filling with new, correctly mixed coolant, would solve all three scenarios.

NOTE: It is possible to test the operation of the thermostat by submerging it in boiling water in a clear container (that can withstand the temperature) and watching to see that it opens cleanly. Removing it from the water you should be able to watch it close again. If it doesn't move, it's faulty.

  • thanks a lot for your recommendation. will check that out today and will get back it does not resolve my problem. – Aay Que Nov 29 '18 at 11:42
  • Thanks for pointing out my problem, I wish I had 10,000 points for you. Today the temperature of the car was good but still if faced a little bit jerk. is there anything else without the thermostat(Previously there was no thermostat). – Aay Que Dec 3 '18 at 5:41

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