Coolant Mysterious Leak

[juussttin]

Hey,

Couldn't seem to find a thread about this but my coolant is leaking at a remarkable rate at the moment. It is at the point where I have to top it up with water twice a week.

I took it to a mechanic to have a look for the issue. He pressure tested the system an entire afternoon, it had no issues, he inspected all the hoses/system and couldn't find any signs of cracks or leaks, so he replaced they top cap (hoping it was maybe the pressure release) and asked me to keep an eye on it.

I have been topping it up with water on and off for like 6 years now starting with a little bit once a year and now at the point where I am constantly doing it is it possible that I have diluted the coolant so much that it is evaporating, meaning I should do a flush and replace all the coolant? or is it a bigger issue?

Thanks,

Justin

[Bora Sport]

I’ve recently been seeing a lot of people with various types of VDubs that are losing water. The common thread seems to be the water pump leaking. A pressure test should have found that though. The only other thought is if you have the twin charged engine then it could have a small head gasket failure. This could be pressurising the cooling system and pumping the coolant out. You should be noticing a drop in performance and poor idle if that was the case.

[juussttin]

I’ve recently been seeing a lot of people with various types of VDubs that are losing water. The common thread seems to be the water pump leaking. A pressure test should have found that though. The only other thought is if you have the twin charged engine then it could have a small head gasket failure. This could be pressurising the cooling system and pumping the coolant out. You should be noticing a drop in performance and poor idle if that was the case.

I have a 77TSI I was having idle issues also, the engine light would come on and and I would loose performance. I would turn the car on and off and it would fix the issue until it happened again. I had a connector thou replaced under transmission for something and it fixed that issue. However it did happen again the other day but that was the first time it had happened in like 6 weeks. I also have a kind of whine/whistle (not the turbo) when accelerating from like 80kms onwards.

[Volksie]

Same issue here. Coolant dissapear every 3 to 4 weeks. Top up about 500ml. Did a pressure test at vw dealership but no issues were found. But me polo have over 200k on the clock. Could be the age

[Transporter]

Same issue here. Coolant dissapear every 3 to 4 weeks. Top up about 500ml. Did a pressure test at vw dealership but no issues were found. But me polo have over 200k on the clock. Could be the age

The experienced and properly equipped mechanic should be able to find where is it leaking from. I say, go elsewhere, there are many cooling testing tools in the market and mechanics should have them. So, even if you losing less than what you said the coolant always leaves the trace.

[Sydneykid]

Where are you topping up the radiator fluid? At the radiator itself or at the overflow (coolant reservoir) tank? When a pressure test is done it only tests the pressure from the radiator cap and around the engine. Any leaks in the coolant system are then identified that way. Pressure testing will not find a leak between the radiator and the coolant reservoir as that is not part of the pressurised system.

I'd suggest carefully checking out the hoses from the reservoir to the radiator and see if there are any leaks there.


Cheers
Gary

[Transporter]

Where are you topping up the radiator fluid? At the radiator itself or at the overflow (coolant reservoir) tank? When a pressure test is done it only tests the pressure from the radiator cap and around the engine. Any leaks in the coolant system are then identified that way. Pressure testing will not find a leak between the radiator and the coolant reservoir as that is not part of the pressurised system.

I'd suggest carefully checking out the hoses from the reservoir to the radiator and see if there are any leaks there.


Cheers
Gary

The cooling system type you described is usually found in Japanese and Korean cars

...however the cooling systems in 6R, 6C have pressurised expansion reservoirs, therefore all under pressure and when you pressure test it with a simple cooling system pressure tester after engine reaches operating temperature (thermostat opened), you’ve pressure tested it all.
Also the radiator doesn’t have the cap and there’s only 1 opening for adding the coolant and that is at pressurised reservoir.