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I drive an old Daihatsu Charade 1993. Just 2 days ago, I heard a bubbling sound from the coolant when I turned off the machine. I didn't really care much until yesterday when the car got hot abnormally (3/4 of the gauge, usually 1/4) while idling, though the heat did lessen when the car moving, but it does imply the car has a trouble. Looking back, I guess it has something to do with the bubbling noise I had heard.

When I checked the coolant container I saw the liquid is still at just below max level which is fine, no leaking on the ground as well.

I drove again this morning, the car didn't get hot and I didn't hear the bubbling anymore, so I thought there wasn't any severe problem (I might be too optimistic). However, that symptom came back again just now when I drove for around 10 minutes. This time I noticed the coolant level got even higher, I still don't have any idea why, but surely it wouldn't be the head gasket thingy since I saw no leaking at all.

Now, as I did some research, there is a tendency saying this is a problem with the radiator cap being melt down or not being pressurized enough, but I'm not sure if it exactly is the case.

I think it'd be better to ask on here before bringing my car to the mechanic so I know the scope of the problem.

Please help if you know, any guesses would do.

nogias
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1 Answers1

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I suspect you have a leaking head gasket, you don't have to see the coolant leak because it can leak into the combustion chamber and exit your vehicle in the form of vapor from the tail pipe. It can also leak into the oil so make sure to check the oil for contamination.

It could also be as simple as a bad radiator cap, you can test them with specialized equipment but they are so cheap I'd just replace it and see if the problem goes away. The job of the radiator cap is to allow the coolant system to pressurize to raise the boiling point. If the cap doesn't' allow the system to pressurize or reduces the amount of pressurization it can allow the coolant to boil and could be the bubbles you are seeing.

There is also an easy way to check the head gasket. They make a combustion gas leak detector that detects CO2 in the coolant indicating a leaking head gasket.

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Uview Combustion Leak Tester

Here is a video of how it works

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