Coolant gradually decreases, is it normal? Cultus Carby

[faheemakbar18]

Aslam o Alikum

I'm losing the coolant gradually.

My car details:
Cultus 2007 Carburetor Engine
Auto Fan
Thermostat in place
5w30 Oil
Liquimoly Coolant (8 months old)

I am facing this strange problem. I check the coolant almost daily and there's no noticeable difference. But, then on one day I can notice a gradual decrease.

I have looked but couldn't spot any place with coolant signs except for the reservoir top.

This picture was taken 15 days ago, when I drove it for around 10km and there's some wetness below the cap. (maybe you can see it in the picture)

Now today, I checked again and there's coolant decreased and the top of reservoir has spots of coolant:

The red indicates the coolant being reduced in last 15 days and around 200km of usage)
its hot that's why bit up, it will go back to the bottom point of red line once cooled down

If its overflowing, shouldn't it leave through the dedicated pipe. It happens more with AC, or maybe when in traffic for long.

I do top up with the distilled water every time it reaches the lower point.

What it could be? the reserve cap? or something else, or nothing at all. Its just how it is?

[pwuser166331039855]

The pictures are not downloading and I cannot notice anything.
But generally if the coolant is reducing slowly then its possible there is a minor leak in the system which is not detectable visually.

Such leaks only happens when system is under pressure (car is running at its optimum temperature).

There is a simple way to give air pressure of 10-12 psi to the system. And observe from where its leaking. It might be an old pipe, a clamp, or radiator tank, or heater core, etc.

Which city you are from?

[Thinking]

usually coolant decreases at low pace due to non visible leak. better approach is to keep it topped up at weekly inspection. it will stop once u identify the leak and get it fixed.

for now since the leak is minor, its much more difficult to find it, so just keep a check at the coolant for the time being.

[faheemakbar18]

I detected some leakage in the reservoir near the cap, and I have replaced it. Now waiting to notice something in few days.

[faheemakbar18]

Yes, I just replaced the reservoir bottle with its cap because that's where I found the leak (very small)

Now waiting to see any more reduction

[pwuser166331039855]

I detected some leakage in the reservoir near the cap, and I have replaced it. Now waiting to notice something in few days.

Nope. The cap of expansion/reservoir bottle cannot cause coolant reduction. Because there is no pressure it holds.
All the coolant pressure is upto the cap of Radiator only.
And the tiny pipe you see which is attached very close to Radiator cap and goes to expansion bottle, there is no pressure in it actually. Its mechanism is connected with radiator cap. When the pressure is high, the rad. Cap spring shrinks and it transfer the coolant into expansion bottle and vise versa.

Plz never ignore these small leaks. It may bring a big damage out of nowhere.

I was observing the same minor leak in my premio and luckily found the leak by giving pressure to the system at workshop of Osama (PW ID is Syncview). I will make a separate thread in premio’s section today. Do read it too since I took many photos of whole procedure to find leaks by giving pressure.