Kühlmittelverlust über die Heizung beim Polo 9N | Posts 32+

I don't understand that either.

The smell might not have any causal connection to the cylinder head gasket (ZKD), or what abstract connection could there be? Is it leaking due to excessive pressure? If so, would it be a permanent issue?

TDI-GTI-4-Motion wrote:

Why would someone replace the gasket when there's a clear smell of coolant, indicating a leak?

1. Because the smell only occurs briefly at the beginning of a journey in heating mode (when the engine is cold!), but surprisingly, nothing is smelled anymore with a warm engine (and increasing cooling system pressure), which contradicts what one would expect from a normal leak.

"Because the dryness of the exposed water tubes and surrounding air ducts, and the absence of white coolant deposits (as far as I could see), cannot, in my opinion, explain the extent of water loss that has occurred recently."

3. Because the excessively high cooling system pressure in the case of a head gasket defect seems like a plausible explanation for a leak at the water pump flange that only occurs under overload conditions and which might disappear again with normal pressures in the cooling system:

Autoservice wrote:

The sealing of the heat exchanger would then also be extremely stressed......

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Why didn't you bridge the WT as originally planned?

Because, given the initially more likely diagnosis of a "ZKD defect" (see above), I thought it would be more sensible to carry out a quick repair rather than continuing to drive for weeks with the possibility of expensive damage: namely,
a. from the combustion chamber dome (ZKD) to the cylinder head (ZK), if the suspected combustion pressure flow path penetrates too deeply into the sealing surface of the ZK.
b. if the water loss suddenly increases to the point where the engine overheats severely and the cylinder head warps before the driver realizes the seriousness of the situation.

matthiasTDI96 wrote:

The smell might not have any causal connection to the timing chain tensioner (TCT), or what abstract connection could there be? Is it leaking due to excessive pressure? If so, wouldn't it be a constant issue, or?}

There is a certain weakness in these explanations.
However, I believe it's possible that coolant could be forced out through the water pump flange on the engine side and then gradually work its way along the valve cover gasket, etc., into the ventilation system. This would explain why the smell only appears in the interior after a significant delay, long after our typical drives (about ½ hour) have ended.
Translation: The portion of the leaking fluid that has reached cooler surfaces instead of evaporating on the hot parts of the WT flange will only have a short-lived odor when starting. By the time any noticeable smell arrives, the vehicle will already be stationary again.

ulf wrote:

1. Because the smell only occurs briefly at the beginning of a journey when the heating is on in "cold" mode (!), but surprisingly, nothing is smelled anymore with a warm engine (and increasing cooling system pressure), which would be expected with a normal leak.

Please don't forget: the nose also gets used to smells and stops noticing them, or notices them only very little, after a certain time.

TDI-GTI-4-Motion wrote:

Please don't forget: the nose gets used to smells, and after a certain time, it no longer perceives them or barely perceives them at all.

I know. But if this effect were playing a trick on me here, the olfactory sensation would have to re-emerge after a sufficiently long period of "muffling."
The pauses can be created (strangely enough) by turning up the heating. However, since the engine is still cold while the smell is present, it doesn't heat up anyway.
By repeatedly switching between cold and warm settings, you can reactivate the scent. However, it will eventually disappear on its own after about 5 minutes from the start of the journey.
After that, even prolonged heating won't help, and turning it to the cold setting prevents the smell from returning.
This also applies to breaks, for example, a multi-hour walk (which should certainly be enough to clear the nose of any lingering odors), followed by a return trip: in that case, I no longer notice any coolant smell at all.
It will probably take at least a day for the smell to disappear.

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3. Because the excessively high cooling system pressure in the case of a head gasket defect seems like a plausible explanation for a leak at the water pump flange that only occurs under overload conditions, and which may disappear again when normal pressures are present in the cooling system.

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Then I drove about 4 km on a country road, pushing the accelerator as much as possible, and again checked the pressure of the coolant flow = not clearly higher than before. I opened the expansion tank again, and only a small amount came out. So, a clear difference compared to before? I would rather say: there is no significant difference compared to before.

Um, I don't quite understand. Did he have the symptoms of a blown head gasket, or not?

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By repeatedly rotating it from cold to warm and back to cold, you can reactivate the scent again and again – until it automatically disappears after approximately 5 minutes of driving. After that, even prolonged heating won't help, and when you turn it to cold, the smell doesn't start again.

As far as I know, the heat exchanger is constantly being flushed with both cold and hot fluids.
As soon as it gets warm/hot, it seals up again. Possibly, coolant is dripping onto the area where cold air flows through.

Autoservice wrote:

Quote: So, a clear difference compared to before? I would rather say: no significant difference compared to before. Öm, I don't quite understand. Did he now have the symptoms of a defective head gasket or not?

Ah, apparently we are not talking about the same "before".
You probably mean before and after the ZKD repair; my reference is to the hose crimp test before and after letting the cows graze for 4 kilometers.

I haven't felt a radiator hose that firm since before your ZKD repair -> so there is a difference, but this check has been quite incomplete until now.

The tire pressure was roughly the same before and after the 4 km run -> no clear difference.

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As far as I know, the heat exchanger is constantly being flushed (with both cold and hot fluids). As soon as it gets warm/hot, it seals again. Possibly, coolant is dripping there where the cold air flows through.

The constant flow of air through the heat exchanger is correct.
It could potentially be as you suspect, but after I spilled about half a liter of water in the area before the repair, it seems highly unlikely that this amount would completely disappear without any trace (other than some odor) from the ventilation duct, meaning without anything accumulating at the lowest point or in the surrounding car carpeting.
To access the WT (presumably a component), you have to remove the "oil pan" of the ventilation unit, and that was completely dry, just like the carpet.

@Ulf,

For me, the head gasket damage wasn't 100% clear yet, because I was missing what I would consider "definitive" feedback (strong overpressure, etc.). Now, in contrast to before (before the repair ), almost no pressure is building up anymore, so the head gasket was probably defective.

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It is hardly conceivable that this amount could completely disappear from the ventilation duct without leaving any traces (except for a smell), i.e., without anything accumulating in the deepest part (or in the car's carpeting around it).

That's not what it was intended for. Even small amounts are enough to produce the smell.

Update:

Earlier, I checked again for any signs of leaks in the area of the water pump (WT). On the engine side, at the very bottom of the pipes, directly in front of the water pump flange, I found a significant amount of pinkish slime that smelled like coolant.

Unfortunately, I don't know whether these traces date from before the ZKD-Rep. era, or whether it continued to leak afterwards.
"Anyway, I've now bypassed the water thermostat (by short-circuiting the coolant hoses on the engine side), and for now, the car will be driven without heating to see if there is still a coolant leak."

If the coolant leak stops, what would your recommendations be for the water heater (which needs to be reconnected by winter at the latest)? Should I replace everything including the pipes, or just replace the seals, or...?


BTW: If the timing chain tensioner wasn't actually defective, then perhaps the repair, including the timing belt replacement, was worthwhile after all.
The timing belt was already 8 and a half years old, and according to the 120,000 km service interval, it would likely have been replaced at around 10-11 years of age -> perhaps this action saved us from engine failure due to a crack in the aged timing belt.
The new ZK screws from ARL comply with the OEM standard based on load requirements.
(You have to find something to be happy about, )

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If the coolant loss stops now, what would your recommendations be for the water heater (which needs to be reconnected by winter at the latest): Should everything, including the pipes, be replaced, or just the seals replaced, or...?

Pressurize with 1 bar of compressed air as far as possible. Spray soapy water on it... (similar to patching a bicycle tire) and first see where the leak is. If it's only the O-rings, I would also just replace those (if accessible from the engine compartment).
If the WT needs to be expanded, everything must be renewed .

Autoservice wrote:

Press with 1 bar of compressed air.

BTW: At what overpressure does the pressure relief valve on the expansion tank actually release?

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At what pressure does the pressure relief valve of the expansion tank actually release?

Try it out . It should be around 1.3 bar.

A pressure of 1 bar will allow an intact well to survive.

Hi Ulf,
I came across your sentence:

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The cylinder head gasket (ZKD) was replaced (and at the same time, the timing belt tensioner (ZR) was also replaced with a new one), and the cylinder head (ZK) was reinstalled using the stronger 12.9 grade screws from an ARL engine.

You might have a problem by using cylinder head bolts of a higher strength class. The 12.9 grade bolts have a higher tensile strength. You may not even reach that value with the tightening torque specification for the existing engine, but in any case, the tensile stresses achieved through angle-controlled tightening are higher, and possibly uneven.
My recommendation: go outside again.
hg
Herbert.

Herbert wrote:

Hi Ulf, I came across your sentence: Quote: The cylinder head gasket (ZKD) was replaced (and at the same time, the timing belt tensioner (ZR) was also replaced with a new one), and the cylinder head (ZK) was reinstalled using the stronger 12.9 grade screws from an ARL engine. You might have a problem by using cylinder head bolts of a higher strength class. The 12.9 grade bolts have a higher tensile strength. You may not even reach that value with the tightening torque specification for the existing engine, but in any case, the tensile stresses achieved through angle-controlled tightening are higher, and possibly uneven. My recommendation: go outside again. hg Herbert

.
The ARL is essentially the same as its engine.

Best regards, Rainer.

Herbert wrote:

You might have a problem installing cylinder head bolts of a higher strength class. The 12.9 grade screws have a higher tensile strength limit. You may not even reach this value with the tightening specifications for the existing engine, but in any case, the tensile stresses achieved through torque-angle tightening are higher, and possibly uneven.

I know what you mean, but...
The ARL has the same key features as the ASZ.
"I've heard of some modified ASZ engines that were retrofitted with aftermarket connecting rod bolts, but I haven't yet encountered any subsequent problems related to the cylinder head or cylinder head gasket."

"Edit: See also Rainer's response."

Please provide the German text you would like me to translate into English. I will then give you only the translation, without any explanations.


Earlier, I removed the pipes leading to the water treatment system and found one defective section: see item No. 1 in the attachment below. Therefore, the pipes definitely need to be replaced.

I'm not entirely convinced that this is the sole cause of the water loss. The used test hose had black deposits in it, for which I haven't found any other explanation besides soot from combustion gases, which again suggests a problem with the cylinder head or head gasket.
On the other hand, I have never noticed any soot particles in the expansion tank .

We would greatly appreciate any further insights or opinions you may have.

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2. I have heard of some modified automatic transmissions that were later fitted with ARL screws, but I haven't yet encountered any subsequent problems in the area of the torque converter/clutch disc.

The screws have been working even with the softer AJM engine block for the past 7 years. An increased oil consumption due to possible thread damage in the engine block has also not occurred.

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Because black grime had accumulated in the used test tube, for which I have so far found no other explanation than soot from combustion gases, which again suggests a problem with the cylinder head or cylinder head gasket. On the other hand, I have never noticed any soot particles in the expansion tank icon_eek.gif

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If it was soot, that's fine. --> Still, continue to monitor the situation.

If it's oil droplets, the oil/water heat exchanger (oil cooler) would be a likely culprit.
If this were to leak badly, it would be a real mess.
Okay, I'm ready. Please provide the German text you want me to translate into English. Just paste it here, and I will give you the translation.

Autoservice wrote:

If it's oil droplets, then the oil/water separator (oil cooler) would be a likely candidate... /viewtopic.php?t=26278

At least, that's not how it looks with the Polo, because the symptom

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In this vehicle, the coolant reservoir is completely full to the top edge with verschandeln black engine oil

hasn't even shown up in a drip yet, and those would have to be floating on top.
I haven't noticed any water on the dipstick so far either.

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If it was soot, that's okay. --> but continue to monitor it.

Makes sense!