Hello All,

 

I noticed some rapid loss of coolant from my Skoda Superb 2 recently so I started looking around. I kept my car ON and in idling with bonnet opened for checking on the leak. After sometime, the coolant in the reservoir (expansion tank) rose up inside the tank and started overflowing though the cap. Anyone has any idea of this behavior? The leak only happens when the car is ON. The hoses seem to be fine as no leak signs are spotted and no leak happens when car is OFF.

 

Thanks in advance.

Edited 14 April, 20206 yr by kunalvaidya

Could have numerous causes. Generally coolant rising in the reservoir is due to excess pressure in the cooling system or the coolant is getting too hot and expanding.

 

Excess pressure can be due to combustion gasses leaking into the coolant, but usually with a blown head gasket, when starting the engine with the cap off, depending on the severity I have seen it blow the coolant out of the expansion tank like a fountain, but when it is that bad they don’t start.

You coolant pump impeller may be spinning on its shaft or vanes worn out so no flow in the system causing overheating.

Could have a stuck thermostat either for the engine OR the DSG gearbox if it has one.

The radiator fan may not be running either due to mechanical blockage or loss of electrical feed or earth.

The cap may no longer be able to hold pressure resulting in overheat.

These are just a few to get you thinking.

 

Hey Thanks for your reply, I was just checking around, seems radiator fan is functioning, but I do see that my cap has a broken piece of plastic which keeps the rubber ring in place. Not sure if that can cause such thing.

That would be a nice cheap fix, the cap should hold the pressure in the system, I have a tool which screws on and checks it holds pressure and that the safety valve works. If it has a crack I would replace it anyway, even if it isn’t the cause, you may be lucky. 👍

Thank for this, I will replace the cap and update if that fixes the issue although may take some time due to lockdown in our country due to COVID19. Very bad to have a broken down car in middle of lockdown 😞

Which country are you in and are you a healthcare worker? In the UK you will get FREE AA cover even if you are not a member IF you work for the NHS and need the car to get to work. I think TPS offer an emergency supply of parts via AA or Roadside Assistance if you are going to or from work.

India, here everything is shutdown. We can go out only to buy medicines or travel to hospital. I dont need the car but in case of emergency I was thinking. I do have a Skoda RSA cover, which is similar to AA I think. But that is also of no use in lockdown.

 

Edited 16 April, 20206 yr by kunalvaidya

If your car has the Maxidot display you might be able to get a quick read on the performance of the cooling system by enabling the oil temperature display.

Yes it has Maxidot display, normally it shows around 103 C (217 F) temperature for oil

Update - I just tried to fix expansion tank cap ring it seemed to be in bad shape and it worked, no more coolant leak. The fix is only temporary, I will change the cap once the lockdown is over but till then seems it was a quick and easy fix