Coolant Leak AFN at Full Load - Head Gasket?

Hello!

After reviewing all the possible posts here about coolant loss, my suspicions are now also leaning towards a blown head gasket.
First, let's start with the initial situation:


-Coolant reservoir was at the maximum level.
- Over the next 500 kilometers, there was a significant amount of high-speed driving.
-Now, the level has dropped by approximately 3/4 of a liter.
- After a longer drive, a hissing sound can be heard with the coolant reservoir cap closed.
-When the lid is opened, it makes a relatively quiet hissing sound. It's as if the pressure isn't very high.
- After releasing the pressure and traveling 1 km, this hissing sound can be heard, and when opening...
very little pressure is escaping.
- No traces of coolant leakage were found in the engine compartment, nor underneath the car.
- Engine oil level remains constant.
- No air bubbles visible in the open container when the engine is idling.
- The coolant is clear and free of oil contamination.


Okay, that was the input .

Perhaps you could provide me with some troubleshooting methods that could lead to the cause.
Could it be that the valve in the lid is opening too early, which is causing the hissing sound?
But then we should be able to see traces of antifreeze around the cap.

Or do I need to prepare for a ZKD replacement?

Does anyone have a repair manual or guide for this hard drive replacement?

It would be nice if someone could help me, because driving with reduced load just to save water and antifreeze is no longer fun .

Best regards, and have a pleasant evening. Christox.

Hello.
It's possible that only the cap is faulty because the system isn't under much pressure. If it were a head gasket or water pump issue, it would create a lot of pressure, causing a loud hissing sound and overflowing.
I would start by testing a new or different lid.
Best regards,
Dirk

Okay, I'll probably do that first before I start taking things apart.

Best regards, Christox.

Of course, it wasn't the lid!
Today, with the new cap installed, I drove on the highway at full speed for about 20 kilometers and lost roughly half a liter of coolant.
On the way back, maintaining a constant speed of 120 km/h, with zero coolant consumption!
So, does everything now point to a blown head gasket, or is there a crack in the cylinder head?

Does anyone have a guide for replacing the timing belt or head gasket on an AFN engine? Also, what are the torque specifications?
What type of screw heads do the terminal block screws have? Are they Torx screws?
What special tools are needed besides the locking tools for the timing belt?

It would be great if someone could help me, because as a student, it's not easy to come up with the €1000 needed for the repair at the dealership.



Best regards, Christox.

Hello.


It seems like there are some AFN los Wochos .

I'm currently experiencing the same phenomenon with my car's coolant system (refill). For some time now, I've also been losing coolant under higher load. The coolant reservoir cap has already been checked -> it's OK. However, I manually adjust the coolant level (SB) forward quite a bit during cold starts and low load. Strangely (or logically ), I experience more coolant loss, or rather, a greater amount of coolant leakage, when the coolant level is adjusted forward. By moving the coolant level forward, the peak pressures inevitably increase, which can then allow combustion gases to more easily enter the coolant system compared to 'normal' pressure conditions. In my opinion, this indicates a slowly weakening head gasket. I don't see any bubbles in the coolant reservoir at idle and at higher RPMs. However, such a 'test' at zero load is not very informative. The coolant also doesn't smell like exhaust gases.

It would be interesting to have more information about the mileage, including how much of it was driven with a trailer, the driving profile, and any potential modifications to the fuel injection system (mechanical, manual, or software-related, etc.).

Good evening, Arno!

My Passat has 140,000 km on the odometer, of which 5,000 km were driven using biodiesel.
The injection timing was adjusted by 1.5° earlier, despite the use of a 2-tank system. This is a relatively small adjustment compared to the 4° earlier adjustment that can be made with a 1-tank system.

Or do you already see this as a 'potential source of problems' for ZKD (zero-pressure, zero-leakage device) failures?

Should I reset the SB (service brake) to the standard setting and observe the KW (wheel load), or should I just address the issue properly and replace it?

...Still looking for tips on how to replace the timing belt/chain...


Best regards, Christox.

Quote:

So, does everything now point to a blown head gasket, or is it a crack in the cylinder head?

I think it's about 80% done, possibly including the ZK (likely referring to a specific task or component) and maybe some head-scratching/problem-solving.

A qualified professional should be available for the repair.

Despite having a 2-tank system, the start of the injection was adjusted by 1.5° earlier through adaptation.
I also think that 1.5° is not critical, especially with PÖL. In contrast, my forward placement is beyond good and evil .

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

I'm sorry, but I cannot provide a translation without the text you would like me to translate. Please provide the text from the URL you mentioned, and I will be happy to translate it for you.

In my opinion, the two threads are the most helpful for identifying and resolving the problem. At least, that was the case with my test .

The second link is really helpful, thank you!

Today, I had a friend pressure-test the cooling system at 2 bar in his workshop --> It's leak-free.
We also performed a CO test, which yielded a negative result. Interestingly, the test fluid changed color more strongly from my breath than from the coolant vapors.

Can this CO test rule out a head gasket leak?

The oil doesn't rise to the surface, and it doesn't form a gray film.

The kilowatt (kW) consumption today was not above 50 kW at speeds of 140 km/h, but it did exceed that level under full load.

Best regards, Christof.

Quote:

Today, I had a friend pressure test the KW system at 2 bar in his workshop --> It's leak-free.

What are you trying to achieve with a pressure of 2 bar? To detect a leak in the cylinder head or cylinder head gasket, you would need to build up a pressure that is equal to...
Burn pressure equals pressure.

Quote:

Can I rule out a head gasket leak using this CO test?

Theoretically --> Yes, Practically --> Unfortunately, no.



Please read this:

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While these are PD engines, the problem is the same as with the VE engines.

What are you trying to achieve with 2 bar pressure?

--> Only the KW system was connected to the atmosphere. Because after the CO test, the mechanics in the workshop thought that the gas must either escape into the oil or leak out.
I may not have expressed myself clearly.

The only splashes I see are coming from under the KW container.
There, a single drop always accumulates at the overflow nozzle at the bottom, likely condensed steam.

Now I only have two options left:

a) Remove the Pöl-2Tank grapple and request a repair from the seller, as the trailer was purchased from a commercial dealer 5 months ago.

b) Do not remove the Pöl-2Tank rake, and instead, armed with a head gasket, water pump, screws, and a timing belt kit, retreat to the garage for a weekend.


Option a) is still associated with some frustration, as the dealer tried to sell me a used car warranty, according to which I have already 'missed' two service appointments.
This WENA warranty covers service at authorized dealerships, and the customer needs to have the stamp mailed to them on a postcard.

However, doesn't the seller still have a legal warranty obligation even without these services?


Best regards, and thank you for your help.

Now I have certainty.

--> Pressure was released from the coolant reservoir while the engine was still warm.
--> After driving at full throttle on the highway for 10 km, the engine compartment was full of steam, which was coming from the pressure relief valve on the radiator cap. When the cap was opened, gases escaped, causing the fluid level in the reservoir to rise. A quick sniff revealed a smell of exhaust fumes.

So, it's the ZKD after all.

Regarding the CO2 test.

When testing, you need to accelerate strongly a few times to allow the engine to build up proper pressure (it's difficult at idle, but still possible). After that, it will start displaying CO2 readings, but that issue seems to be resolved now.

Quote:

However, the seller's legal warranty still exists even without these services, right?

You're confusing warranty and guarantee.

The warranty covers defects that were present at the time of delivery. And if the water pump was already defective upon delivery, you would have had to immediately report a water leak (which would have already existed). However, it seems that was not the case. Therefore, my opinion is that there is no legal recourse.

Hello!

Okay, the head is now facing down.
The head gasket doesn't show much visible damage, except that it appears to be more corroded in the area where the water channels are located. However, the two outer pistons are discolored white over a large area on the side where the water channels run.
Is that an indication of water ingress into the combustion chamber?
I've now prepared the head for planing and pressing, and it will go back in tomorrow.

Best regards, Christox.