Kühlmittelverlust über die Heizung beim Polo 9N | Posts 48+

Current status:

Within approximately 2 weeks and about 400 kilometers of driving on country roads, there was no more noticeable water loss, which is a huge improvement compared to before.

What still confuses me somewhat is the apparent water vapor leakage from over the lid of the equalization tank, see.
Okay, I understand. Please provide the German text you want me to translate into English. I will only provide the translation.

However, the lid from the Ibiza (part number 3B0 121 321) now stays dry on the Polo container, and conversely, the lid from the Polo (part number 1J0 121 321 B) also becomes condensation-wet on the Ibiza container – as if the 1J0 121 321 B has a lower opening pressure.

I'm going to exchange the caps again. If the ASZ continues to produce excessive steam, I will replace its cap with a 3B0 cap, and hopefully that will resolve the issue.

Has this been discussed before? Does the Polo have a cooled EGR system? The Golf ASZ only has it as an automatic transmission option...

matthiasTDI96 wrote:

Has this been discussed before? Does the Polo have a cooled EGR system?

No, the Polo's EGR system is not cooled.
What connection do you see with the water loss?

Were the pipes leaking? I wouldn't be surprised, considering how poorly those welds were done.

RedR32 wrote:

Were the pipes leaking? I wouldn't be surprised, given those sloppily prepared welds.

Yes, see https://community.dieselschrauber.org/en/viewtopic.php?t=26626&start=45.

"It's being completely ruled out just because of a potential leak..."

Okay, approximately one and a half years after replacing the water pump with new ARL head bolts and a new coolant hose set to the heater core, our engine suddenly starts losing a significant amount of coolant again .
I just disconnected the heating circuit again (or short-circuited it on the motor side) to rule out this potential failure area, while we will carefully monitor the water level in the coming days.

However, the pipes leading to the heating system are completely dry this time. If the leak were to reappear in the heating area, then the water tank would have to be leaking.

Does anyone have a suggestion as to what it might be this time?
The engine has now covered approximately 115,000 kilometers (about 71,000 miles), and the aforementioned repairs, including a complete timing belt replacement, were carried out about 15,000 kilometers (approximately 9,300 miles) ago.

Quote:

Would anyone like to offer a suggestion about what it might be this time?

What amount of water loss are we talking about?
Have you ever taken a look at the radiator and the hoses?

Autoservice wrote:

What kind of water loss are we talking about?

The order of magnitude is approximately 0.5 liters for an estimated 3,000 kilometers driven, mostly at a comfortable speed on country roads.

Quote:

Have you ever taken a look at the radiator and the hoses?

Not specifically. However, I tend to rely more on my sense of smell in the engine compartment, as it's quite sensitive to the smell of coolant.
Now that summer is here, the large cooling circuit opens up, and if there were a leak somewhere causing the aforementioned loss, I'm quite sure I would be able to smell the unpleasant coolant odor when opening the hood in the still air of the garage... but there's nothing like that.
By the way, unlike the interior: when I ride in it (it's now my partner's car), I still notice a coolant smell on the first few kilometers, strangely enough only when the heating is set to cold (there's no air conditioning).
If I turn up the heating, the smell of coolant disappears immediately. When I switch it back to cold air, the smell returns until it dissipates after a few kilometers.
However, it has never really stopped since those repairs were carried out. Therefore, I believe that there are still coolant residues in the foam seals around the heater core, which evaporate into the cold air duct of the ventilation system when the car is stationary, and then cause a smell during the first few kilometers.

My better half, who usually seems to have a very sensitive sense of smell when it comes to unpleasant odors, doesn't notice the annoying coolant smell at all .

Update:
To further pinpoint the cause, I just removed the fan mounting plate behind the water cooling system. And indeed: in the middle, between the water blocks, the cooling mesh is wet. Touching it and smelling it confirms that it's definitely coolant, meaning at least one of the lower water channels is leaking.
The resulting smell in the engine compartment is so subtle that I haven't consciously noticed it .

"Question: Are there any known cases where leaks like these in aluminum radiators suddenly become much larger, causing a sudden and significant loss of coolant within just a few kilometers, potentially leading to engine overheating?"
The background is that my partner is scheduling the radiator replacement, and until next weekend, there's practically no opportunity .

Hello Ulf,

If the area isn't corroded (i.e., mechanically stable), I would take the risk if it were my car. I would simply bring a few liters of water just in case.

Best regards, Rainer.

dieselschrauber wrote:

If the area is not corroded (i.e., mechanically stable), I would risk it

. Therefore, the radiator is not yet prone to breakage.

Meanwhile, I've been doing something else:
In the attic, I found a nearly new water cooling system (about 20cm narrower, designed for a 9N 1.4L gasoline engine) from when I was planning to install an intercooler next to the narrow water cooling system on my Polo.
I've now installed it, but I had to improvise a bit with the mounting. To prevent air from flowing around the narrow cooler, I inserted a piece of plastic.
The compact cooler (width = 43 cm instead of 63 cm), which allows for unimpeded airflow, is estimated to provide a similar cooling performance to the wider standard AIO liquid cooler with its air conditioning radiator that was used previously, so the ASZ should not constantly run at the edge of overheating .

According to the test drive, everything seems to be working well, and now I can take some time to consider whether the Polo should eventually get a proper automatic transmission cooling system.
Or am I completely wrong in my estimate of the cooling performance (that increasing the network width by about 50% would roughly compensate for a pre-placed air conditioning capacitor), such that the Polo should soon receive a full-size water cooling system again?